-----------------------------------------
07 Ford 500...............................            O           192               113               (24 km/h)
                                                                       -----------------------------------------
07 Ford Edge..............................            O           129     (24 km/h)       No data     (24 km/h)
07 Ford Edge..............................            N           148       No data            67       No data
07 Ford Expedition........................            O           151      To Stops           137     (24 km/h)
07 Jeep Commander.........................            O      To Stops           175           155     (24 km/h)
07 Jeep Commander w/lam...................            O       No data       No data            73       No data
07 Mazda CX9..............................            N            76       No data            67       No data
07 Saturn Vue.............................            O      To Stops           130           191            28
08 Dodge Caravan..........................            O           112       No data           162     (24 km/h)

08 Ford Taurus X..........................            O           110       No data       No data     (24 km/h)
                                                                       -----------------------------------------
08 Subaru Tribeca.........................            O           180               106               (24 km/h)
                                                                       -----------------------------------------
09 Chevy Equinox..........................            O           149       No data           200     (24 km/h)
Average...................................  ............          140           112           132            15
Standard Deviation........................  ............         36.5          55.7          56.7          39.0
----------------------------------------------------------------------------------------------------------------

                           Table 12--Front Row Window, 16 km/h Impact, 6 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. A1       Pos. A2       Pos. A3       Pos. A4
----------------------------------------------------------------------------------------------------------------
03 Navigator..............................            O      To Stops            74      To Stops           -30
03 Navigator w/lam........................            O           157           -36           137       No Data
04 Volvo XC90.............................            O           161            73            78           -22
04 Volvo w/lam............................            O            96            26            59       No Data
05 Chevy Trailblazer......................            O           121           192           124       No Data
05 Chevy Trailblazer w/lam................            O       No Data           102       No Data       No Data
05 Chevy Trail. w/lam. (4 hole)...........            O       No Data            92       No Data       No Data
05 Honda Odyssey..........................            O       No Data            69            77           -54
05 Infinity FX35..........................            O            88            22            40             9
05 Nissan Pathfinder......................            O           117           104           195            43
05 Toyota Highlander......................            O           205           210           152            69
06 Dodge Durango..........................            O           138           135           167            13
06 Dodge Durango w/lam....................            O       No Data       No Data           142       No Data
06 Dodge Dur. w/lam. (4 hole).............            O            97            58           145       No Data
06 Mercury Monterey.......................            O           222           183       No Data            35
06 Toyota Land Cruiser....................            O           146           207           229            16
06 Volvo C70..............................            O           135     No Target     No Target     No Target
07 Chevy Silverado........................            O           145           244           115            -7
07 Chevy Tahoe............................            O            42             6            10          -136
                                                                       -----------------------------------------
07 Ford 500...............................            O           151               58                      -16
                                                                       -----------------------------------------
07 Ford 500 w/lam.........................            O            96       No Data       No Data       No Data
07 Ford Edge..............................            O           103           -42             7           -56
07 Ford Edge..............................            N           123       No Data            33       No Data
07 Ford Expedition........................            O           141           205           109             3
07 Jeep Commander.........................            O           255           144           136           -89
07 Jeep Commander w/lam...................            O       No Data            56            62       No Data
07 Jeep Commander w/lam. (4 hole).........            O       No Data            50            60       No Data
07 Mazda CX9..............................            O            54           -38            44           -53
07 Mazda CX9..............................            N            67       No Data            31       No Data
07 Saturn Vue.............................            O           184           180           186            72
08 Dodge Caravan..........................            O            85           -39           121          -141
08 Ford Taurus X..........................            O           104           -13            39           -88
                                                                       -----------------------------------------
08 Subaru Tribeca.........................            O           122               77                       -1
                                                                       -----------------------------------------
08 Toyota Highlander......................            O            36             0            54           -62
08 Toyota Highlander......................            N           119       No Data            52       No Data
09 Chevy Equinox..........................            O           125            25           178           -46
Average...................................  ............          125            82            99           -25
Standard Deviation........................  ............         50.1          87.2          61.1          58.1
----------------------------------------------------------------------------------------------------------------

                          Table 13--Second Row Window, 24 km/h Impact, 1.5 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. B1       Pos. B2       Pos. B3       Pos. B4
----------------------------------------------------------------------------------------------------------------
03 Ford Navigator.........................            O      To Stops       No data       No data            40
04 Volvo XC90.............................            O     (20 km/h)       No data       No data            69
04 Volvo XC90 w/lam.......................            O            92       No data       No data            62
05 Chevy Trailblazer......................            O           122       No data       No data            35
05 Honda Odyssey..........................            O           152           193            71            80
05 Infinity FX35..........................            O           148       No data       No data            47
05 Nissan Pathfinder......................            O           167       No data       No data           133
05 Toyota Highlander......................            O           152       No data       No data           154
06 Dodge Durango..........................            O            86            82            76            91
06 Mercury Monterey.......................            O           171           193            72            78
06 Toyota Land Cruiser....................            O           159           157            75     No Target
07 Chevy Silverado........................            O           153     (20 km/h)            78           117

07 Chevy Tahoe............................            O     (20 km/h)           161            24            74
07 Chevy Tahoe w/lam......................            O       No data            48       No data       No data
07 Ford 500...............................            O           184            50           102           157
07 Ford 500 w/lam.........................            O            91       No data       No data           111
07 Ford 500 w/lam. (4 hole)...............            O       No data       No data       No data            99
07 Ford Edge..............................            O            39            21           -22            27
07 Ford Edge..............................            N            51            33       No data            26
07 Ford Expedition........................            O           164            55            66            75
07 Jeep Commander.........................            O           140     (20 km/h)            64       No data
07 Mazda CX9..............................            O            36             2            51             9
07 Mazda CX9..............................            N            22       No data            44       No data
07 Saturn Vue.............................            O     No Target           144            66     No Target
08 Dodge Caravan..........................            O            59            27           -16            -7
08 Ford Taurus X..........................            O            45            34            22            31
08 Subaru Tribeca.........................            O           133            85            80           111
08 Toyota Highlander......................            O           106           110            55           109
08 Toyota Highlander......................            N           125           144       No data           133
08 Toyota High. w/liner...................            N           133           138       No data            77
09 Chevy Equinox..........................            O            72            22            39            45
Average...................................  ............          112            89            53            76
Standard Deviation........................  ............         49.2          63.0          32.7          44.0
----------------------------------------------------------------------------------------------------------------

                          Table 14--Second Row Window, 20 km/h Impact, 1.5 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. B1       Pos. B2       Pos. B3       Pos. B4
----------------------------------------------------------------------------------------------------------------
03 Ford Navigator.........................            O      To Stops       No data       No data           -14
04 Volvo XC90.............................            O           183       No data       No data     (24 km/h)
04 Volvo XC90 w/lam.......................            O            94       No data       No data     (24 km/h)
05 Chevy Trailblazer......................            O            68       No data       No data             8
05 Honda Odyssey..........................            O           134            84            42            34
05 Infinity FX35..........................            O            90       No data       No data            21
05 Nissan Pathfinder......................            O           143       No data       No data           111
05 Toyota Highlander......................            O           110       No data       No data           106
06 Mercury Monterey.......................            O           155            52            42            51
06 Toyota Land Cruiser....................            O           127           128            53     No Target
07 Chevy Silverado........................            O           114           232     (24 km/h)           101
07 Chevy Tahoe............................            O           249       No data     (24 km/h)     (24 km/h)
07 Ford 500...............................            O           152       No data            89           128
07 Ford Expedition........................            O           146            23     (24 km/h)     (24 km/h)
07 Jeep Commander.........................            O           122           107     (24 km/h)       No data
07 Saturn Vue.............................            O     No Target           111            40     No Target
08 Subaru Tribeca.........................            O           105       No data     (24 km/h)       No data
08 Toyota Highlander......................            O       No data            67     (24 km/h)            88
08 Toyota Highlander......................            N            92            89       No data           110
Average...................................  ............          130            99            53            64
Standard Deviation........................  ............         43.4          59.3          20.7          49.9
----------------------------------------------------------------------------------------------------------------

                           Table 15--Second Row Window, 16 km/h Impact, 6 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. B1       Pos. B2       Pos. B3       Pos. B4
----------------------------------------------------------------------------------------------------------------
03 Ford Navigator.........................            O           126       No data       No data           -27
04 Volvo XC90.............................            O           189       No data       No data            29
04 Volvo XC90 w/lam.......................            O            63       No data       No data             9
05 Chevy Trailblazer......................            O           127       No data       No data            47
05 Honda Odyssey..........................            O           121            28            12            55
05 Infinity FX35..........................            O            64       No data       No data            20
05 Nissan Pathfinder......................            O           111       No data       No data            78
05 Toyota Highlander......................            O           143       No data       No data           110
06 Dodge Durango..........................            O            36            18             3            71
06 Mercury Monterey.......................            O           223           142            54            54
06 Toyota Land Cruiser....................            O           107           113            49     No Target
07 Chevy Silverado........................            O           124           194            53            63
07 Chevy Tahoe............................            O           120           -83           -21            15
07 Chevy Tahoe w/lam......................            O            66       No data       No data       No data
07 Chevy Tahoe w/lam. (4 hole)............            O            58       No data       No data       No data
07 Ford 500...............................            O           133            -3            56            94
07 Ford 500 w/lam.........................            O            64       No data       No data       No data
07 Ford Edge..............................            O           -16           -40           -76           -25

07 Ford Expedition........................            O            89           159            22            34
07 Jeep Commander.........................            O           107            99            27            57
07 Mazda CX9..............................            O           -15           -58             5           -35
07 Saturn Vue.............................            O       No data           138            26       No data
08 Dodge Caravan..........................            O           -58           -29           -55           -56
08 Ford Taurus X..........................            O           -17           -19           -13           -40
08 Subaru Tribeca.........................            O            76            19            28            20
08 Toyota Highlander......................            O            49            59            32            57
08 Toyota Highlander......................            N            87           105       No data            93
09 Chevy Equinox..........................            O            15           -51             1           -14
Average...................................  ............           81            44            12            31
Standard Deviation........................  ............         63.9          84.5          37.2          46.8
----------------------------------------------------------------------------------------------------------------

                          Table 16--Third Row Window, 24 km/h Impact, 1.5 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. C1       Pos. C2       Pos. C3       Pos. C4
----------------------------------------------------------------------------------------------------------------
05 Honda Odyssey..........................            O       No data     (20 km/h)       No data           175
06 Mercury Monterey.......................            O           188     (20 km/h)           119       No data
06 Toyota Land Cruiser....................            O             NC            NC          180             NC
07 Chevrolet Tahoe........................            O            91     No Target           194     No Target
07 Chevrolet Tahoe w/lam..................            O       No Data           106           141       No Data
07 Ford Expedition........................            O     (20 km/h)       No data            81           186
07 Jeep Commander.........................            O           229           155           120           102
08 Dodge Caravan..........................            O           -42           112            35           -41
08 Ford Taurus X..........................            O     No Target      To Stops            48     No Target
08 Toyota Highlander......................            O           -42            42            92       No data
08 Toyota Highlander......................            N       No data       No data           110       No data
08 Toyota Highlander w/liner..............            N       No data       No data            42       No data
Average...................................  ............           85           104           106           106
Standard Deviation........................  ............        126.1          46.6          53.1         104.5
----------------------------------------------------------------------------------------------------------------

                          Table 17--Third Row Window, 20 km/h Impact, 1.5 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O*         Pos. C1       Pos. C2       Pos. C3       Pos. C4
----------------------------------------------------------------------------------------------------------------
05 Honda Odyssey..........................            O       No data      To Stops            58           122
06 Dodge Durango..........................            O       No data      To Stops            66       No data
06 Mercury Monterey.......................            O           147           212            75       No data
06 Toyota Land Cruiser....................            O             NC            NC          128             NC
07 Chevrolet Tahoe........................            O            58     No Target       No data     No Target
07 Ford Expedition........................            O           241       No data       No data            51
07 Jeep Commander.........................            O       No data           115           102       No data
08 Ford Taurus X..........................            O     No Target            86     (24 km/h)     No Target
08 Toyota Highlander......................            N       No data       No data            88       No data
Average...................................  ............          149           138            86            86
Standard Deviation........................  ............         91.5          66.0          25.8          50.6
----------------------------------------------------------------------------------------------------------------

                           Table 18--Third Row Window, 16 km/h Impact, 6 Second Delay
----------------------------------------------------------------------------------------------------------------
                  Vehicle                       N/O *        Pos. C1       Pos. C2       Pos. C3       Pos. C4
----------------------------------------------------------------------------------------------------------------
05 Honda Odyssey..........................            O      To Stops      To Stops            44           80.
06 Dodge Durango..........................            O       No Data       No Data            52      No Data.
06 Mercury Monterey.......................            O           186           204           142          225.
06 Toyota Land Cruiser....................            O             NC            NC           98             NC.
07 Chevrolet Tahoe........................            O            30     No Target            64    No Target.
07 Chevrolet Tahoe w/lam..................            O       No Data            57            66      No Data.
07 Ford Expedition........................            O           233       No Data            49           34.
07 Jeep Commander.........................            O           170           104            92           56.
08 Dodge Caravan..........................            O           -91            34           -42         -113.
08 Ford Taurus X..........................            O     No Target            60             7    No Target.
08 Toyota Highlander......................            O       No Data           -23            37      No Data.
Average...................................  ............          106            73            55           56.
Standard Deviation........................  ............        133.4          76.5          48.2        120.6.
----------------------------------------------------------------------------------------------------------------

Trends in Performance of Ejection Mitigation Systems by MY Using Old
Impactor
    Based on the vehicles the agency tested, there appears to be a
trend toward improved performance as each model year passes. This is
demonstrated by increased coverage of the window opening in the more
recent MY vehicles tested and the ability of the countermeasure to
restrain displacement of the impactor. While it is difficult to
quantify this trend, the trend is shown graphically below by plots of
displacement values by model year for the 1st row (Figure 2) and 2nd
Row (Figure 3). These graphs are restricted to the 24 km/h-1.5 second
test using the old impactor and exclude any testing with advanced
glazing.

    Note: Not shown in the figure are data from older vehicles which
often had no curtain coverage at a particular target. If there was
no curtain coverage, we did not test the target since the 100 mm
displacement limit would have been exceeded. Although these vehicles
are not shown on the graph, their improved curtain coverage in
recent MY vehicles is indicative of improved performance over time.

    Since the graphs span multiple vehicles, there is scatter in the
data. Nonetheless, when a trend line is plotted through the data for
each impact location it shows decreasing displacement for newer models.
[GRAPHIC] [TIFF OMITTED] TR19JA11.001

[GRAPHIC] [TIFF OMITTED] TR19JA11.002

    One comparison to note for illustration purposes is the improved
performance of the MY 2008 Highlander in comparison to the MY 2005
Highlander. Table 19 shows the change in displacement values for the
two model years of the Highlander at each target location and across
impact speeds. The largest change in displacement value was for the 16
km/h tests at targets A1 and A2 (169 mm and 210 mm, respectively). On
an average basis, the MY 2008 Highlander had 103 mm less displacement
across all tested target locations, for a 76 percent overall reduction.
This is illustrative of the improved performance of later MY vehicles.
We believe that the MY 2008 Highlander had increased coverage of the
ejection mitigation curtain and increased size of the inflated chambers
which helped to restrain the impactor.

  Table 19--Old Impactor, Absolute and Percentage Change in Displacement (mm) Between MY2005 and MY2008 Toyota
                                                   Highlander
----------------------------------------------------------------------------------------------------------------
                Test vel.                     A1          A2          A3          A4          B1          B4
----------------------------------------------------------------------------------------------------------------
24......................................  ..........         -96         -88        -104         -46         -45
16......................................        -169        -210         -98        -131         -94         -53
                                         -----------------------------------------------------------------------
Average (mm)............................                                   -103
----------------------------------------------------------------------------------------------------------------
24......................................  ..........        -70%        -62%        -90%        -30%        -29%
16......................................        -82%       -100%        -64%       -190%        -66%        -48%
                                         -----------------------------------------------------------------------
Average (%).............................                                   -76%
----------------------------------------------------------------------------------------------------------------

Comparing Results of Tests With Old and New Impactors
    Several vehicles (the MY2008 CX9, Edge and Highlander) were tested
using both the old and new impactor.
    Table 20 shows the difference in displacements measured at target
locations where both impactors were used.\55\ Not surprisingly, these
data generally indicate that the new impactor tends to result in
greater displacement (positive difference); we believe this is due to
lower dynamic friction. Yet, the old impactor displacement exceeded the
new impactor (negative difference) at several targets as well.
---------------------------------------------------------------------------

    \55\ In some cases average values were used to calculate the
differences.
---------------------------------------------------------------------------

    The CX9 was the only vehicle that was impacted multiple times at
the same targets by both the old and new

impactor. A student's t-test was performed to determine if the
difference in the results were significant.\56\ Table 21 shows the
displacement values and statistics for targets A1 and A3. The
difference in displacement was statistically significant (p<=0.05) for
the A1 target, but not the A3 target.
---------------------------------------------------------------------------

    \56\ The one sided t-test was performed assuming equal variance
to determine if the new test device had produced larger displacement
values compared to the old device.

                                         Table 20--Change in Displacement Between Old and New Impact Test Device
--------------------------------------------------------------------------------------------------------------------------------------------------------
                 Vehicle                        Test vel. (km/h)          A1          A3          B1          B2          B3          B4          C3
--------------------------------------------------------------------------------------------------------------------------------------------------------
08 Ford Edge.............................  24.......................        29.0        69.0        12.0        12.0  ..........        -1.0  ..........
08 Mazda CX9.............................  24.......................        15.5         3.0       -14.0         0.0        -7.0         0.0  ..........
08 Toyota Highlander.....................  24.......................        38.5        23.0        19.0        34.0  ..........        24.0        18.0
08 Ford Edge.............................  20.......................        18.5  ..........  ..........  ..........  ..........  ..........  ..........
08 Toyota Highlander.....................  20.......................  ..........  ..........  ..........        22.0  ..........        22.0  ..........
08 Ford Edge.............................  16.......................        19.5        26.0  ..........  ..........  ..........  ..........  ..........
08 Mazda CX9.............................  16.......................        13.0       -13.0  ..........  ..........  ..........  ..........  ..........
08 Toyota Highlander.....................  16.......................        83.0        -2.0        38.0        46.0  ..........        36.0  ..........
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                           Average..................        31.0        17.7        13.8        28.5        -7.0        20.3        18.0
--------------------------------------------------------------------------------------------------------------------------------------------------------
                             Average All                                                  21.6
--------------------------------------------------------------------------------------------------------------------------------------------------------

                                   Table 21--Impactor Comparison for Mazda CX9
----------------------------------------------------------------------------------------------------------------
                                                          A1                                  A3
            Test Vel. (km/h)             -----------------------------------------------------------------------
                                                 Old               New               Old               New
----------------------------------------------------------------------------------------------------------------
24......................................                94               110                84                90
                                                        98               113                89                89
Average.................................              96.0             111.5              86.5              89.5
Std.....................................               2.8               2.1               3.5               0.7
                                         -----------------------------------------------------------------------
P-Value.................................                 0.013
                                                         0.180
----------------------------------------------------------------------------------------------------------------

    Despite the differences in test results, the test results from the
old impactor provided useful data to assess the relative performance of
ejection mitigation countermeasures. The results from the impactor are
useful when analyzing data obtained from the old impactor alone, to
compare vehicles to each other or to previous model year vehicles, or
compare data from impact points on a vehicle.
Research Testing With New Impactor
    As part of our analysis of the data, we evaluated data from only
the new impactor to avoid confounding the comparison of data by
impactor differences. Table 22 shows the change in displacement between
the 24 km/h-1.5 second, 20 km/h-1.5 second and 16 km/h-6 second tests
at various target locations for the MY 2007 Edge, MY 2007 CX9 and MY
2008 Highlander. The 24 km/h-1.5 second test always had greater
displacement than the 20 km/h-1.5 second test. On average this
difference was 38.3 mm when averaged over all vehicles and target
locations. This is an expected result because the only difference is
the impact speed.

              Table 22--New Impactor, Change in Displacement (mm) Between 24 km/h 1.5 Second, 20 km/h 1.5 Second and 16 km/h 6 Second Tests
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                         Test
                              Vehicle                                 comparison      A1          A3          B1          B2          B4          C3
--------------------------------------------------------------------------------------------------------------------------------------------------------
07 Ford Edge.......................................................        24-20          28          88  ..........  ..........  ..........  ..........
07 Mazda CX9.......................................................        24-20          36          23  ..........  ..........  ..........  ..........
08 Toyota Highlander...............................................        24-20  ..........  ..........          33          55          23          22
07 Ford Edge.......................................................        24-16          53         122  ..........  ..........  ..........  ..........
07 Mazda CX9.......................................................        24-16          45          59  ..........  ..........  ..........  ..........
08 Toyota Highlander...............................................        24-16         -17          25          38          39          40  ..........
07 Ford Edge.......................................................        20-16          25          34  ..........  ..........  ..........  ..........
07 Mazda CX9.......................................................        20-16           9          36  ..........  ..........  ..........  ..........
08 Toyota Highlander...............................................        20-16  ..........  ..........           5         -16          17  ..........
                                                                    ------------------------------------------------------------------------------------
Average All--24-20..............................................................                       38.3
Average All--24-16..............................................................                       44.7
Average All--20-16..............................................................                       15.7
--------------------------------------------------------------------------------------------------------------------------------------------------------

    There were only two vehicles/target locations that had more than
one impact at multiple test speeds. Although this is extremely limited
data, they allow a t-test to be performed.\57\ The results are given in
Table 23. The results indicate that the 16 km/h-1.5 second impact had
statistically significant less displacement than both the higher speed
tests at target A1.
---------------------------------------------------------------------------

    \57\ The one sided t-test was performed assuming equal variance
to determine if the 24 km/h impact produced larger displacement
values compared to the 20 km/h impact.

          Table 23--New Impactor, Comparison of Target A1 Displacement as a Function of Impact Velocity
----------------------------------------------------------------------------------------------------------------
             Vehicle                                CX9                                    Edge
----------------------------------------------------------------------------------------------------------------
            Test Type               16 km/h-6 sec.     24 km/h-1.5 sec.     16 km/h-6 sec.     20 km/h-1.5 sec.
----------------------------------------------------------------------------------------------------------------
                                                  75                 110                 126                 152
                                                  59                 113                 119                 143
----------------------------------------------------------------------------------------------------------------
Average.........................                67.0               111.5               122.5               147.5
Std.............................                11.3                 2.1                 4.9                 6.4
----------------------------------------------------------------------------------------------------------------
P-Value.........................                   0.016
                                                   0.024
----------------------------------------------------------------------------------------------------------------

b. Field Performance

    The agency evaluated available crash data to better understand the
field performance of the current fleet equipped with side curtain air
bags. A focus of this evaluation was the performance of the rollover
sensors and their ability to detect the rollover event and activate
deployment of the side curtain air bags. We also sought to understand
the occupant containment provided by the vehicle system. Several
sources of available data were reviewed. These included detailed
analysis on a limited number of rollover crashes by NHTSA's Special
Crash Investigation (SCI) division, case reviews of NASS CDS cases from
the target population of the final rule, and data from a new Rollover
Data Special Study project. Detailed reviews of some of these cases can
be found in the technical report accompanying this final rule.
SCI Cases Presented in the NPRM
    The following seven SCI cases were discussed in the NPRM. The
agency's SCI division analyzed seven real-world rollover crashes of
Ford vehicles where the subject vehicles contained a rollover sensor
and side curtain air bags. (Ford had agreed to notify SCI of the
crashes.) The subject vehicles were Ford Expeditions, a Ford Explorer,
a Mercury Mountaineer, and a Volvo XC90. Table 24 gives details about
each case.
    In each case, the rollover sensor deployed the side curtain air
bag. Of the seven cases, there were a total of 19 occupants, 15 of whom
were properly restrained. All were in lap/shoulder belts, except one
child in a rear facing child restraint system (CRS). A single crash
(DS04-016) had all of the unrestrained occupants, serious injuries,
fatalities and ejections in this set of cases. Two of the four
unrestrained occupants were fully ejected from the vehicle, resulting
in one fatal and one serious injury. The fatality was a 4-month-old
infant, seated in the middle of the 2nd row. The ejection route was not
determined. The seriously injured occupant was an adult in the left 3rd
row, ejected through the uncovered right side 3rd row window. One non-
ejected, restrained occupant received a fatal cervical fracture
resulting from roof contact and another was seriously injured. The
injuries to the remaining occupants were ``none'' to ``minor.''

                                                                                Table 24--Ford SCI Rollover Cases (Presented in the NPRM)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Occupants                                                                            Deploy
              Case                     Make            Model            MY       ------------------------------------------------   \1/4\ Rot.   ---------------------------------------------------------------------------------------
                                                                                Row 1           Row 2           Row 3                           Angle                   Time (ms)                         Rate (deg/s)
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
CA02-059........................  Mercury.......  Mount.........  2002..........  1R............  1R............  ..............  1.............  17............  ..................................                            17 to 25
CA04-010........................  Ford..........  Expl..........  2003..........  1R............  ..............  ..............  1.............  43............                                  20                                  75
IN-02-010.......................  Ford..........  Exped.........  2003..........  1R............  ..............  ..............  2.............  45............                                 146                                 111
2004-003-04009..................  Ford..........  Exped.........  2003..........  1R............  2R............  ..............  5.............  Yes...........                             Unknown                             Unknown
DS04-016........................  Ford..........  Exped.........  2003..........  2R............  2R,             1R,             5.............  Yes...........                             Unknown                             Unknown
                                                                                2NR[dagger].    2NR[dagger].
DS04017.........................  Ford..........  Exped.........  2004..........  1R............  ..............  ..............  12............  Yes...........                             Unknown                             Unknown
2003-079-057....................  Volvo.........  XC90..........  2003..........  1R............  1R............  ..............  6.............  Yes...........                             Unknown                             Unknown
----------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
R = Restrained, NR = Not Restrained.
[dagger] One NR 2nd and 3rd row occupant ejected (total of 2 ejected).

Rollover Data Special Study (RODSS)
    RODSS is a new source of rollover crash data that began in April
2007. NHTSA initiated RODSS as a pilot project to obtain additional
field data for rollover crashes not covered by other agency databases.
Cases were identified through the FARS database. NASS CDS and SCI cases
were excluded from consideration because detailed information from
those crashes would be available from those databases. However, remote
SCIs were performed on selected cases.\58\ The technical report for
this final rule includes a discussion of the RODSS study conducted for
this final rule.
---------------------------------------------------------------------------

    \58\ A remote SCI is one where, for a variety of reasons, the
investigator is not able to physically examine the crash location
and vehicles. The investigation is done through the use of police
accident reports, scene diagrams and photographs.
---------------------------------------------------------------------------

    RODSS is not a random sample and is not intended to be
statistically representative of all rollover crashes nationally. Also,
the sample size is small and becomes even smaller when separating the
data into subcategories. Accordingly, observations based on the RODSS
data about the relationship of side curtains and ejection are
inherently limited.
    To become part of the RODSS sample, the vehicle had to be exposed
to a rollover crash and have a side curtain air bag and/or electronic
stability control (ESC)/rollover stability control (RSC). The curtain
air bag did not have to be deployable in a rollover, i.e., the curtain
air bag could be an FMVSS No. 214 side impact air curtain without a
rollover sensor, but some vehicles did have a rollover sensor.
    The study first reviewed a total of 328 crashes occurring in 2005
through 2008. Of these 328 case vehicles, 315 were coded as exposed to
a lateral rollover. Of these 315 case vehicles, 115 were believed to be
equipped with side curtain air bags. Of these 115 case vehicles, 21
were believed to have a rollover sensor (rollover curtain). Of these 21
case vehicles, 18 had their curtains deploy during the rollover and 3
did not. These three cases of non-deployment are of interest relative
to sensor performance and will be discussed in more detail later, along
with a non-deployment SCI case.
    Curtain deployment coding was tied to the driver or passenger,
i.e., if there was someone seated on the side of the vehicle where the
curtain deployed, it was coded as deployed for that occupant. There
were 120 side curtain air bags deployed adjacent to occupants of the
vehicles (58 drivers and 62 passengers). Limiting RODSS occupant
selection to those in vehicles exposed to a lateral rollover, and those
who had a known ejection status, then separating by known curtain
deployment, results in Table 25, below. This table shows 119 occupants
(57 drivers and 62 passengers) who were exposed to a curtain deployment
and 496 (244 drivers and 252 passengers), who were not.

  Table 25--RODSS Driver and Passenger in Lateral Rollovers With Known
               Ejection Status by Known Curtain Deployment
------------------------------------------------------------------------
                                                                  All
          Curtain deployment             Drivers   Passengers  occupants
------------------------------------------------------------------------
Yes...................................         57          62        119
No....................................        244         252        496
                                       ---------------------------------
    Total.............................        301         314        615
------------------------------------------------------------------------

General Observations From RODSS About Ejection Rates Relative to
Curtain Air Bags
    Again, any observations made based on the RODSS data about the
relationship of side curtains and ejection must be prefaced by the fact
that RODSS is not a random sample and is not intended to be
statistically representative of all rollover crashes nationally.
    The data from the 615 occupants in Table 25 form the basis of a
comparison on ejection status versus curtain air bag deployment found
in Tables 26 and 27. The ``curtain deployed'' group is made up of
vehicles that had a rollover sensor and vehicles that did not (the
latter vehicles may have had a side impact sensor only). The ``curtain
not deployed'' group is made up of vehicles equipped or not equipped
with a curtain, i.e., one possible reason for the curtain not deploying
is that it did not exist.
    We studied the data to see if side curtains had an effect in
mitigating rollover ejections. We were aware that care should be taken
in drawing conclusions from these results. Most of the curtain-equipped
vehicles exposed to lateral rollovers had only FMVSS No. 214 side
impact curtains (94 vehicles), rather than rollover curtains (21
vehicles). It is possible that if a side impact curtain deployed during
the crash, the crash might be different than a crash where a side
impact curtain did not deploy. An important difference when examining
ejection data is rollover severity as quantified by number of quarter-
turns. To help determine if there was an obvious bias in the data, we
examined the difference between the quarter-turns in the rollover
crashes where the side impact curtains deployed and the number of
quarter turns in the rollover crashes where they did not deploy.
    RODSS data indicate that deployment of any curtain (even a side
impact curtain) has a positive effect on reducing the rate of side
window ejection. Table 26 shows that 10.9 percent [13/119] of all
occupants adjacent to a curtain air bag deployment were ejected through
the side windows, in comparison to 27.6 percent [137/496] of those
occupants who were not adjacent to a curtain deployment.
    Restricting the data to occupants protected by a curtain deployed
by a rollover sensor, 5.3 percent [2/38] were ejected. The cases
involving the two occupants who were ejected, even though the rollover
curtain deployed, are discussed in a later section.

[GRAPHIC] [TIFF OMITTED] TR19JA11.003

    Table 27 examines the subset of occupants from Table 26 who were
unbelted. Table 27 shows that 22.7 percent [10/44] of unbelted
occupants in vehicles with curtain air bag deployment were ejected
through the side windows, in comparison to 51.9 percent [108/208] of
those unbelted occupants in vehicles where the curtain did not deploy.
Rollover severity (as represented by number of quarter-turns) does not
seem to account for the difference in the ejection rates for these two
unbelted groups.
    When the data are restricted to only unbelted occupants protected
by rollover curtains, 10.0 percent [1/10] were ejected through the side
window, as compared to 26.5 percent [9/34] of unbelted occupants
protected by side impact curtains. We note that two unbelted occupants
were not ejected in vehicles with deployed rollover curtains.
[GRAPHIC] [TIFF OMITTED] TR19JA11.004

Cases Where Occupants Were Ejected Through Rollover Curtain-Equipped
Windows
    We examined SCI rollover crashes, NASS CDS cases from the target
population of the final rule and data from the RODSS project and found
six case vehicles where occupants were ejected through the side window
opening that a rollover deployed curtain presumably covered. These
cases are listed in Table 28, along with the number of quarter turns,
occupant seating position, belt use, occupant age, degree of ejection,
ejection route, and level of injury.
    The average number of quarter-turns was 5.5. These six crashes
involved nine occupants, six of whom were partially or completely
ejected through a protected side window. Four occupants were partially
ejected and two were completely ejected. All six were front seat
occupants, although one was ejected through a second row window. Four
of the ejected occupants were killed in the crash. One fatal partial
ejection was ejected through a window protected by both a curtain and a
laminated window. Four of these cases involved curtain damage. In two,
the A-pillar tether detached. It is not possible to know if these
instances of curtain damage occurred during the rollover or post-crash
due to extrication.

               Table 28--RODSS, NASS CDS and SCI Cases With Occupants Who Were Ejected Through Side Windows Protected by Rollover Curtains
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                 1/4                      Seat
         Case ID            Year/Make/Model     Turns     Curt. depl.     pos.      Belt use      Age        Eject.          Route         Injury/ MAIS
--------------------------------------------------------------------------------------------------------------------------------------------------------
          RODSS

7238 *..................  06 Ford Explorer...        6  Yes...........       11  No...........      84y  Comp.........  Row 1 L........  Fatal.
8289 *..................  03 Lincoln Aviator        8+  Yes...........       11  Yes..........      62y  Part.........  Row 1 L........  Fatal.
                           [Dagger].
8289 *..................  03 Lincoln Aviator        8+  Yes...........       12  Yes..........      28y  No...........  NA.............  Serious.
                           [Dagger].
8289 *..................  03 Lincoln Aviator.       8+  Yes...........       23  Yes..........      65y  No...........  NA.............  Moderate.

        NASS CDS

2003-04-048 *...........  02 Ford Explorer...        4  Yes...........       11  Yes..........      54y  No...........  NA.............  1.
2003-04-048.............  02 Ford Explorer...        4  Yes...........       13  Yes..........      49y  Part.........  Row 1 R........  1.
2006-79-089.............  04 Lexus RX330.....        1  Yes...........       11  No...........      27y  Part.........  Row 2 L........  Fatal.
2008-03-108.............  08 Honda Pilot.....        6  Yes...........       11  No...........      48y  Part.........  Row 1 L........  3.
2008-12-159.............  05 Mercury Mont....        8  Yes...........       11  No...........      23y  Comp.........  Row 1 L........  Fatal.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* These are also SCI cases.\59\
[Dagger] These seating positions had laminated glazing adjacent to them.

Non-Deployed Rollover Curtains in Rollover Crashes
---------------------------------------------------------------------------

    \59\ Both RODSS cases were made into SCI remote investigations
to facilitate documentation of photographs and other crash details.
The SCI case numbers are CA09069 (RODSS 7238) and CA10006 (RODSS
8289).
---------------------------------------------------------------------------

    We examined SCI rollover crashes, NASS CDS cases from the target
population of the final rule and data from the RODSS project to find if
the rollover sensors deployed the rollover side air curtains in a
rollover. In general, field data indicate that rollover sensors have
been recognizing a rollover and deploying rollover curtains in rollover
crashes.
    We found five case vehicles where the vehicle was apparently
equipped with a side curtain air bag that was supposed to be deployed
by a rollover sensor and the curtains did not deploy in the rollover
event (see Table 29). There were two completely ejected occupants and
one partial ejected occupant in these crashes. The results of these
ejections were 3 fatalities. All of these ejections were through side
windows except one where the front passenger door was dislodged from
the vehicle and provided the ejection route for the unbelted driver.
    Consistent among these non-deployment cases is that the rollover
was preceded by a significant frontal impact. Four of the five non-
deployment cases had a significant frontal impact that preceded the
rollover. The MY 2006 Ford Explorer in RODSS case 6121 had a right
front corner impact with a large tree prior to the rollover. The MY
2003 Lincoln Aviator in RODSS case 7242 had an offset frontal impact
with an oncoming vehicle prior to the rollover. The MY 2006 Cadillac
SRX in SCI case DS07009 impacted a large tree prior to the rollover.
The EDR data from this case indicated that the tree impact had a
longitudinal and lateral [Delta]V of - 38.9 mph and - 10.2 mph,
respectively. The EDR also indicated that the rollover sensor status
was ``invalid'' and the curtain deployment was not commanded. The MY
2009 Dodge Journey had a narrow offset frontal impact with another
vehicle, which the crash investigator stated disrupted the power supply
from the battery. The frontal air bags deployed in the above four
crashes. (There is some doubt as to whether RODSS case 6121 (SCI
CA9062) was definitely equipped with a rollover sensor, since the
system was an option on this vehicle. Ultimately, no definitive
determination was made.) For the cases involving initial frontal
impacts, these impacts may have destroyed the vehicle battery and thus
eliminated the primary power source for deploying the rollover curtain.
    In RODSS case 5032 (SCI CA9061), it appears the sensor may not have
been able to make a determination that a rollover occurred. However, in
studying the details of this case, the vehicle's kinematics were very
complex and may have included some motion not typical of a lateral
rollover.

                                    Table 29--RODSS and SCI Rollover Cases Where the Rollover Curtain Did Not Deploy
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                               Quarter                    Seat
         Case ID            Year/Make/Model     turns     Curt. depl.     pos.      Belt use      Age        Eject.          Route         Injury/ MAIS
--------------------------------------------------------------------------------------------------------------------------------------------------------
          RODSS

5032 *..................  04 Lincoln Aviator         3  No............       11  No...........      68y  Comp.........  Row 2 R........  Fatal.
                           [Dagger].
6121 *..................  06 Ford Explorer...        4  No............       11  No...........      23y  Comp.........  Door (13)......  Fatal.
7242 *..................  03 Lincoln Aviator         3  No............       11  Yes..........      28y  No...........  NA.............  Serious.
                           [Dagger].
7242 *..................  03 Lincoln Aviator         3  No............       13  Yes..........      26y  No...........  NA.............  Serious.
                           [Dagger].
7242 *..................  03 Lincoln Aviator.        3  No............       21  CRS..........       3y  No...........  NA.............  Serious.
7242 *..................  03 Lincoln Aviator.        3  No............       23  Yes..........       7y  No...........  NA.............  Serious.

           SCI

DS07009.................  06 Cadillac SRX....        4  No............       11  No...........      81y  Part.........  Row 1 L........  Fatal.
DS09071.................  09 Dodge Journey...        4  No............       11  Yes..........      63y  No...........  NA.............  2.
DS09071.................  09 Dodge Journey...        4  No............       13  Yes..........      60y  No...........  NA.............  1.
--------------------------------------------------------------------------------------------------------------------------------------------------------
* These are also SCI cases.\60\
[Dagger] These seating positions had laminated glazing adjacent to them.

X. Response to Comments and Agency Decisions
---------------------------------------------------------------------------

    \60\ These three RODSS cases were made into SCI remote
investigations to facilitate documentation of photographs and other
crash details. The SCI case numbers are RODSS 5032 (CA09061), RODSS
6121 (CA9062) and RODSS 7242 (CA9063).
---------------------------------------------------------------------------

    Laboratory and field data indicate that window curtains covering
side windows can substantially reduce ejections in rollovers. NHTSA
issued the NPRM to require that the side windows next to the first
three rows of seats be subject to performance requirements that ensure
the vehicle has an ejection mitigation countermeasure that would
prevent an 18 kg headform from moving more than 100 mm beyond the zero
displacement plane of each window when the window is impacted.
    The NPRM proposed requirements for: (a) The impactor dimensions and
mass; (b) the displacement limit; (c) impactor time and speed of
impact; (d) target locations, and (e) testing the targets. We also
discussed: (f) glazing issues; (g) test procedure tolerances; (h) test
device characteristics; and (i) a proposal for a telltale requirement.
The NPRM did not specifically require a rollover sensor. A 3-year lead
time and 4-year phase-in was proposed, along with allowance of advanced
credits to meet phase-in requirements. Costs, benefits, and other
impacts were discussed in a PRIA accompanying the NPRM.

a. Impactor Dimensions and Mass

1. NPRM
    The component test involves use of a guided linear impactor that is
designed to replicate the loading of a 50th percentile male occupant's
head and upper torso during ejection situations. The portion of the
impactor that strikes the countermeasure is a featureless headform that
was originally designed for the upper interior head protection research
program (FMVSS No. 201).\61\ It averages the dimensional and inertial
characteristics of the frontal and lateral regions of the head into a
single headform. The NPRM specified that the headform is covered with
an approximately 10 mm thick dummy skin material whose outer surface
dimensions are given in Figure 4, below. The Technical Analysis report
accompanying the NPRM discusses other dimensional attributes of the
headform, such as the curvature of the outer surface.
---------------------------------------------------------------------------

    \61\ ``Ejection Mitigation Using Advanced Glazings: A Status
Report,'' November 1995, Docket NHTSA-1996-1782-3; ``Ejection
Mitigation Using Advanced Glazings: Status Report II,'' August 1999,
Docket NHTSA-1996-1782-21; ``Ejection Mitigation Using Advanced
Glazings: Final Report,'' August 2001, Docket NHTSA-1996-1782-22.
---------------------------------------------------------------------------

    There are many possible ways of delivering the impactor to the
target location on the ejection mitigation countermeasure. Both the old
and new impactors used in agency research propel the shaft component of
the impactor with a pneumatic piston. The shaft of the old impactor
slides along a plastic (polyethylene) bearing. The new impactor uses
curved roller bearings for part of the shaft support, which reduces the
energy loss due to friction. The impactor has an 18 kg mass.\62\
---------------------------------------------------------------------------

    \62\ Since the performance criterion for this ejection
mitigation standard is a linear displacement measure (a linear
displacement measure would correlate to the actual gap through which
an occupant can be ejected), a linear impactor is a suitable tool to
dynamically measure displacement. The impactor can be placed inside
the vehicle for testing the ejection mitigation curtains and glazing
covering window openings.
[GRAPHIC] [TIFF OMITTED] TR19JA11.005

    The mass of the guided impactor was developed through pendulum
tests, side impact sled tests, and modeling conducted to determine the
mass imposed on the window opening by a 50th percentile adult male's
upper torso and head during an occupant ejection (``effective
mass'').\63\ Briefly, the pendulum impact tests were conducted on a
BioSID anthropomorphic test device (50th percentile adult male) to
measure effective mass of the head, shoulder, and upper torso. The
BioSID was chosen because it was originally configured for side impact,
unlike the Hybrid III dummy, and has a shoulder which the Side Impact
Dummy (49 CFR 572, subpart F) used for FMVSS No. 214, ``Side impact
protection,'' does not have. A linear impact pendulum weighing 23.4 kg
was used to strike the head and shoulder of the dummy laterally
(perpendicular to the midsagittal plane) using two impact speeds (9.7
and 12.9 km/h) and four impact surfaces. In addition to the rigid
impactor face, three types of padding were added to the impactor face
to increase the contact time and replicate advanced glazing impacts.
---------------------------------------------------------------------------

    \63\ ``Technical Analysis in Support of a Notice of Proposed
Rulemaking for Ejection Mitigation,'' supra.
---------------------------------------------------------------------------

    Effective mass was calculated by dividing the force time history
calculated from the pendulum accelerometers by the acceleration time
history from the dummy sensors. In general, higher speed impacts and
impacts with softer surfaces generated higher effective mass. Based on
these pendulum tests, a range for the effective mass of the head and
upper torso was estimated to be 16 to 27 kg.
    In the sled tests, we used a side impact sled buck with a load
plate representing a door and two load plates representing the glazing
to measure shoulder and head impacts with three different stiffness
foams. The purpose of these tests was to determine the effect lower
body loading would have on the combined head and upper torso effective
mass. Two impact conditions were simulated, one condition was described
as being representative of a rollover event and the second was
described as being representative of a side impact event.
    In the rollover condition, the impact speed was intended to be 16.1
km/h (10 mph) and the dummy was positioned leaning towards the door
such that the head and torso would contact the simulated glazing at the
same time. This leaning position was intended to be more representative
of an occupant's attitude in a rollover. For the test designed to be
more representative of a side impact condition, the dummy was seated
upright and the impact speed was intended to be 24.1 km/h (15 mph).
    In the preamble of the NPRM, we described the agency's analysis of
these tests as follows. As was done for the pendulum data, the
effective mass was calculated by dividing the force time history
calculated from the pendulum accelerometers by the acceleration time
history from the dummy sensors. Using this method, the effective mass
of the head and upper torso calculated for the 16.1 km/h impact
condition showed a quick rise to about 18 kg by about 5 ms, followed by
an increase to about 40 kg at about 30 ms. The effective mass for the
24.1 km/h impact condition showed an initial artificially high value or
spike prior to 5 ms because of a lag between the force measured in the
load plates and the acceleration measured at the upper spine. This
spike was also seen in some pendulum shoulder impacts. The effective
mass settled to about 9 kg at about 10 ms, with a slow rise to about 18
to 20 kg at about 25 to 30 ms. Looking at the results, we deferred to
the 18 kg effective mass since the test condition more closely
represented a rollover. In addition, the 18 kg value was within the
range of the pendulum impactor results discussed above, which showed an
effective mass range between 16 and 27 kg.
    For this final rule, we have reanalyzed these sled tests primarily
for the purpose of determining impact energy, which we address in
detail later in this preamble.\64\ However, this analysis also
generated estimates of the effective mass of the dummies in these
tests. For the 24.1 km/h test, three methods (represented by equations
2-4, infra) gave a range of the combined head and shoulder effective
mass of 12.2 to 13.1 kg. We believe that a reasonable estimate is 13
kg. The analysis for the 16.1 km/h test is more complex due to the time
dependent dummy orientation. After making estimates of the impact
energy using a simple sprung mass model, we back calculated the
effective mass assuming the impact energy is equal to the kinetic
energy prior to impact (represented by equation 3, infra). We also used
the sled velocity as a surrogate for relative dummy speed and
calculated effective mass directly by using an equation 4, infra. From
these calculations we estimated a combined head and shoulder effective
mass of 22 kg.
---------------------------------------------------------------------------

    \64\ The video from these tests and the data from the dummies,
load wall and sled can be accessed from the NHTSA Biomechanics
Database at http://www-nrd.nhtsa.dot.gov/database/aspx/biodb/querytesttable.aspx. The test numbers are 10282 through 10287. Tests
reanalyzed in detail were 10282 (24 km/h test) and 10285 (16.1 km/h
test).
---------------------------------------------------------------------------

    In the NPRM preamble, we reported that the agency also performed a
computer modeling analysis of an 18 kg impactor and 50th percentile
Hybrid III dummy impacting simulated glazing (foam). The comparison
found that the total energy transferred by the 18 kg impactor was
within the range of the total energy transferred by the entire dummy.
For a 16.1 km/h dummy model impact with the foam, the effective mass
that came in contact with the foam was between 12.5 kg and 27 kg.
    We noted in the NPRM that the 18 kg proposed mass is consistent
with that used by General Motors (GM) in 16.2 km/h (10 mph) tests of
ejection mitigation curtains.\65\ GM based this value on test results
from 52 full-vehicle rollover tests that estimated the effective mass
of occupant contact with the first row side window area. A more
detailed analysis of this study can be found later in this preamble.
---------------------------------------------------------------------------

    \65\ O'Brian-Mitchell, Bridget M., Lange, Robert C., ``Ejection
Mitigation in Rollover Events--Component Test Development,'' SAE
2007-01-0374.
---------------------------------------------------------------------------

    The estimated effective mass for most belted tests was about 5 kg
and all were less than 10 kg. The majority of belted tests had
effective masses which were a combination of both the near and far side
occupants. The effective mass for the unbelted occupants ranged from 5
to 85 kg.
    In summary, the proposed impactor mass was based on the
determination of an effective mass calculated through both pendulum and
sled test impacts and modeling. These methods resulted in a large range
of effective mass values. In the end, we deferred to the 18 kg
equivalent mass seen during the sled test that was intended to be more
representative of a rollover event, which was also the equivalent mass
calculated from pendulum impact into the dummy shoulder. For this final
rule we have reanalyzed the sled tests and estimated a range of
effective mass from approximately 13 to 22 kg. Thus, the 18 kg
effective mass is still considered to be a reasonable representation of
an occupant's head and a portion of the torso. An effective mass more
representative of just the head would be substantially smaller, and an
equivalent mass accounting for more torso and lower body mass would be
substantially more. The 18 kg mass is well within the GM estimates from
vehicle rollover tests, and is consistent with the impactor that GM
uses to evaluate side curtains.

2. Comments
    There was general support from the vehicle manufacturers and
suppliers for using a linear impactor and performance metric based on
the displacement of that impactor in a compliance test. There were only
a few comments on the impactor dimensions and mass. These few comments
were in favor of the proposed mass. While VW and others had comments on
the impact energy imparted by the mass, which is an issue which will be
addressed in a later section below, VW stated that ``the 18 kg mass for
the impactor is well established * * *'' The Alliance referenced the
fact that the GM test procedure for ejection mitigation uses an 18 kg
linear impactor in stating that ``[t]he Alliance supports the use of
the 18 kg headform proposed in the NPRM.''
    Some parties commented on the design of the headform. Takata stated
that simulated animations have shown relative movement of head skull
and headform, and that ``the incomplete fixation of the head skull is
influencing the displacement behavior of the head form [sic].'' Takata
suggested enlarging the head skull fixation in the lower portion, by
adding a skull cap or enlarging the chin area in the rear for example.
Similarly, TRW said that it found that the headform skin can become
dislodged from the skull during testing and suggested using a backplate
of smaller size on the headform to better clamp the headform skin
flange to the skull. TRW also said that the headform skin can become
displaced from the lower (chin) area of the skull.
    AORC recommended that NHTSA adopt specifications for the skin
stiffness, skin friction coefficient, and skull surface finish, to
address the headform skin partially dislocating on the headform as a
result of friction between the countermeasure and the headform.
    TRW suggested changes to the preparation of the headform for
testing. It stated that frictional attributes of the headform skin
affect the manner in which the headform interacts with the rollover
curtain, so talc, chalk, or other coatings could affect test results.
TRW suggested that the standard specify that ``no coatings shall be
applied to the headform skin during testing'' and asked, as did AORC,
that the standard specify that prior to the test, the headform skin
must be cleaned (TRW suggested cleaning the headform with isopropyl
alcohol). TRW suggested changes to the headform drawing package to
address: The outer surface finish requirements of the skull; the
thickness tolerance and durometer hardness of the skin; inner/outer
surface finish and tolerance requirements of the skin material type and
material properties corridor for the skin; the definition of frictional
characteristics of the skin, including the performance corridor; and
test procedure and measurement technique for frictional characteristics
of skin.
3. Agency Response
    We are adopting an 18 kg headform substantially similar to the
device described in the NPRM.
    We are declining Takata's and TRW's requests to add a skull cap or
modify the backplate of the headform. The modification is unnecessary
as the new headform has not exhibited the problem these commenters
describe. Further, the effect of the modification on actual test
results has not been quantified by the commenters. Using modeling,
Takata estimated about a 3 mm increase in displacement between the
proposed headform and one with the suggested modification, but it is
not clear this modeling is representative of an actual impact test.
    NHTSA is not inherently opposed to improvements in the headform
design to possibly allow for a longer period of head skin use before it
needs to be replaced. However, it has not been shown that there is a
need to improve the headform at this time. If improvements are feasible
and the effect of changing the headform on ejection mitigation
countermeasure performance can be better assessed, we are open to
considering fine-tuning adjustments to the headform at a future date.
    With respect to TRW's comments about the additions and revisions to
the drawing package, the NPRM's drawing package already included
specifications for the skin material type, thickness and durometer. It
also included a specification for preparing the outer surface finish of
the skull. TRW did not provide any reason to change these
specifications, so they will remain as proposed in the final rule.
    We deny TRW's other requests that we specify the inner/outer skin
surface finish, skin frictional characteristics, friction performance
corridor and friction measurement technique. We do not believe there is
a need for these specifications. NHTSA has not before found a need to
specify skin surface finish and frictional characteristics for test
dummy skin. The commenter provided no justification as to why the
material properties provided were insufficient or how the requested
parameters would improve the objectivity of the standard.
    We are denying the request to place a requirement in the regulatory
text to clean the headform skin with isopropyl alcohol as per FMVSS No.
201, ``Occupant Protection in Interior Impact.'' The commenters provide
no data showing the necessity of such provision. FMVSS No. 201 has no
requirement that the free motion headform be cleaned with alcohol prior
to the testing. There is no FMVSS that specifies in the regulatory text
that the dummy skin should be cleaned prior to vehicle testing.

b. Measurement Plane and Displacement Limit (100 mm)

1. NPRM
    We proposed that the linear travel of the impactor headform must be
limited to 100 mm from the inside of the tested vehicle's glazing as
measured with the glazing in an unbroken state. The 100 mm boundary
would be first determined with the original glazing ``in position''
(up) and unbroken. Then, for the test, the original glazing would be in
position but pre-broken if it were advanced glazing; or down or removed
altogether if it were tempered glazing. It was proposed that advanced
glazing would be in position but pre-broken for both the 1.5 second
test and the 6-second test.
    The NPRM included a window-breaking procedure that damages but does
not destroy advanced glazing, while it will obliterate tempered
glazing. It was proposed that vehicle manufacturers may remove or
completely retract tempered glazing since it would be destroyed in the
pre-breaking procedure and would have no effect on the ejection
mitigation results. When tested with the original glazing in position
but pre-broken or with the glazing removed, the linear travel of the
impactor headform must not exceed the 100 mm limit. If a side curtain
air bag is present, and we anticipate that most, if not all, vehicles
will have an ejection mitigation curtain, the curtain would be
deployed.
    In the test, the ejection mitigation countermeasure must prevent
the headform from exceeding the 100 mm limit. The principle underlying
the 100 mm displacement limit is to ensure that the countermeasure does
not allow gaps or openings to form through which occupants can be
partially or fully ejected. In the research tests, targets that had
displacements of less than 100 mm did not allow ejections in dynamic
testing.
    In research tests, the TRW and Zodiac prototype ejection mitigation
countermeasures were tested on a CK

pickup to the proposed impactor test procedure.\66\ The TRW prototype
had no coverage at position A1 (front window forward lower position).
These systems were later tested on the DRF with the 50th percentile
male, 5th percentile female and 6-year-old dummies in upright seating
positions, and a prone 6-year-old dummy aimed at approximately the
target positions A1 and A2 (front window rear lower position). When
tested on the DRF, the arms of the upright dummies flailed out of the
window opening up to the shoulder at the sill (A1 and A2) and the prone
6-year-old dummy was completely ejected at A1.
---------------------------------------------------------------------------

    \66\ There were only some slight variations in target locations.
---------------------------------------------------------------------------

    We recognize that dummy ejection did not occur all the time at
targets that had displacements of over 100 mm. When tested with pre-
broken laminated glazing, at position A1, the TRW system had 181 mm of
displacement at the 24 km/h (1.5 second delay) test and 104 mm of
displacement in the 20 km/h (1.5 second delay) test, but did not eject
either the prone or seated dummies in DRF tests. Nonetheless, the
component and DRF testing indicated that there was an increased
likelihood that an opening could be formed between the curtain and the
window opening through which an occupant could be ejected if the
displacement were over 100 mm in the headform test. In addition, a 100-
mm limit would also help guard against the countermeasure being overly
pliable or elastic so as to allow excessive excursion of an occupant's
head and shoulders outside of the confines of the vehicle even in the
absence of a gap.\67\
---------------------------------------------------------------------------

    \67\ The agency further notes that an advantage to the
displacement limit is that the linear displacement of the headform
can be measured in a practicable and relatively straightforward
manner, unlike a real-time dynamic measurement of a gap during an
impact.
---------------------------------------------------------------------------

    NHTSA also noted in the NPRM that a 100-mm performance limit is
used in several regulations relating to occupant retention. In FMVSS
No. 217, ``Bus emergency exits and window retention and release,'' (49
CFR 571.217), bus manufacturers are required to ensure that each piece
of glazing and each piece of window frame be retained by its
surrounding structure in a manner that prevents the formation of any
opening large enough to admit the passage of a 100-mm diameter sphere
under a specified force. The purpose of the requirement is to minimize
the likelihood of occupants being thrown from the vehicle. This value
is also used in FMVSS No. 206, ``Door locks and door retention
components,'' (49 CFR 571.206, as amended 69 FR 75020), to mitigate
occupant ejection through unintentional door openings in a crash. In
FMVSS No. 206, the door is loaded with 18,000 N of force and the space
between the interior of the door and the exterior of the door frame
must be less than 100 mm.
    In addition, NHTSA also considered that a value of approximately
100 mm is used by the International Code Council (ICC) in developing
building codes used to construct residential and commercial
buildings.\68\ The ICC 2006 International Building Code and 2006
International Residential Code require guards to be placed around areas
such as open-sided walking areas, stairs, ramps, balconies and
landings. The guards must not allow passage of a sphere, 4 inches (102
mm) in diameter, up to a height of 34 inches (864 mm). The ICC explains
in the Commentary accompanying the Codes that the 4-inch spacing was
chosen after considering information showing that the 4-inch opening
will prevent nearly all children 1 year in age or older from falling
through the guard.
---------------------------------------------------------------------------

    \68\ The ICC is a nonprofit membership association that works on
developing a single set of comprehensive and coordinated national
model construction codes. http://www.iccsafe.org/news/about/.
---------------------------------------------------------------------------

    The NPRM noted that GM has developed a test procedure that uses a
100 mm displacement limit but in GM's procedure, the zero displacement
plane is a plane tangent to the exterior of the side of the vehicle at
the target location.69 70 Displacement is measured
perpendicular to this excursion plane. Thus, the allowable GM
displacement is approximately 100/cos([thgr]) mm, with [thgr] being the
angle with the vertical of the exterior plane, if other aspects of the
test were identical to those of the NPRM. If [thgr] were 20 degrees,
the GM limit would be approximately 106 mm. The GM method also results
in a slightly different allowable final displacement position than the
proposed method because of the separation between the flat excursion
plane and the inside surface of the window at the target location.
---------------------------------------------------------------------------

    \69\ O'Brian-Mitchell, Bridget M., Lange, Robert C., ``Ejection
Mitigation in Rollover Events--Component Test Development,'' SAE
2007-01-0374.
    \70\ GM explained that its justification for the 100 mm
displacement limit is that it represents half the height of the 50th
percentile male Hybrid III head.
---------------------------------------------------------------------------

2. Comments
    There was general support for the use of a linear impactor as
opposed to some other impacting device and performance metric based on
the displacement of that impactor.\71\ However, many commenters had
opinions about the 100 mm performance limit and how the displacement
should be measured. In general, the net effect of the vehicle
manufacturers' requests was to increase the allowable displacement,
while that of the glazing manufacturers and consumer groups was to
reduce it.
---------------------------------------------------------------------------

    \71\ This is aside from commenters who want the agency to use a
completely different test method, i.e., full vehicle dynamic
rollover.
---------------------------------------------------------------------------

    Both the Alliance and AIAM suggested that the final rule measure
displacement from an initial reference point other than the point of
contact of the headform with the glazing. Both requested that a method
similar to that used by GM be used. This measurement method defines a
line tangent to the side of the vehicle at the window opening. (We note
that although the Alliance calls the longitudinal plane that passes
through this line the excursion plane, see Figure 5, extracted from the
Alliance comments, there would likely be a unique excursion plane at
every target location due to the curvature of the vehicle sides.)
    Under the Alliance method, the headform contact with the excursion
plane for that target location defines the point of zero displacement.
The Alliance explained this zero plane by stating that ``the risk of
injury is more closely tied to the amount of occupant excursion from
the outside of the vehicle's structure as opposed to the side glass.''
The AIAM stated that its procedure ``takes into account the shape of
the vehicle body near the side windows and the contribution the body
makes in providing additional space before the occupant contacts the
ground.''
    The Alliance and AIAM methods differ after the zero excursion plane
is determined. For the Alliance, the maximum excursion plane is defined
by translating the excursion plane 150 mm laterally. The point of
contact of the headform with the maximum excursion plane provides the
limit on displacement. The Alliance justifies its request for a 150 mm
excursion limit by stating ``that the impactor mass and impact energy
are based on the 50th male.'' Therefore, it believes that ``a 150 mm
excursion limit based on the diameter of a 50th percentile male head
(Hybrid III--153 mm, WorldSID = 159 mm, Featureless = 177 mm) is more
appropriate.'' The Alliance and Volvo commented that excursion should
not be based on the size of a child's head and impact energy of an
adult male. For the AIAM, the maximum excursion plane is defined by
translating the

excursion plane by 100 mm along a line normal to the excursion plane,
rather than 150 mm laterally.
[GRAPHIC] [TIFF OMITTED] TR19JA11.006

    Honda agreed with the 100 mm displacement limit in the NPRM because
it believes it to be appropriate to account for the size of a child's
head. It also agreed that the horizontal measurement of the impactor
displacement was appropriate because of its ``feasibility and
measurement accuracy.'' However, Honda concluded ``that the proposed
procedure * * * doesn't accurately simulate the degree of ejection
toward the outside of the vehicle.''
    Honda suggested that the measured displacement should begin at the
same location as proposed in the NPRM, i.e., the point of contact of
the headform with the inside surface of the glazing. However, Honda
suggested drawing a line normal to the glazing at the target
center.\72\ The window cross-section in the lateral plane is then
projected 100 mm along the normal line. The headform is then translated
laterally and horizontally until it contacts the projected window
cross-section, which provides the limit of displacement.
---------------------------------------------------------------------------

    \72\ Honda's diagram in its comment shows a line projected from
the point of contact with the window, rather than the target center.
(The target or target outline was defined in the NPRM as the x-z
plane projection of the ejection headform face. The center of the
target outline would be the target center.) We assume the graphic
represents the intent of Honda's comment. The line emanates from the
point of glazing contact with the headform. Honda also stated that
the line projected from the point of contact is normal
(perpendicular) to the window. However, most side windows curve out
of the longitudinal vehicle plane and any normal to the window would
not be contained in a lateral plane. Thus, we have assumed that only
the component of the normal line in the lateral plane is of
interest, i.e., only the line normal to the lateral cross-section of
the glazing.
---------------------------------------------------------------------------

    TRW agreed with the measurement method and excursion limit of 100
mm, with one caveat. The commenter noted that ``during an impact test,
there can be considerable deflection of the door/window frame, door
structure, door hinges, etc.'' TRW stated that ``[s]ince the objective
of the Standard is to limit headform displacement to no more than 100mm
beyond the zero displacement plane, movement of the plane due to the
door system deflection should be considered during the test.''
    IIHS suggested that the 100 mm displacement limit might be
unnecessarily small. It stated that ``[s]electing this value based on
its use in other safety standards with very different test conditions
or in building codes for guardrails on balconies and stairs may be
unreasonable.'' IIHS indicated that the 12 vehicles tested by NHTSA, as
reported in the NPRM, would have failed to comply with the 100 mm
displacement limit, yet ``the crash performance of these vehicles has
not been assessed to demonstrate a need for improved ejection
mitigation systems.'' IIHS also stated that the potential negative
effects of requiring air bags to be stiffer to meet a 100 mm
displacement requirement are unknown.
    In general, glazing suppliers recommended that the final rule use
the passage of a 40 mm sphere to assess any gaps in the
countermeasures. They suggested we use industry standards published by
the Society of Automotive Engineers (SAE), SAE J2568, ``Intrusion
Resistance of Safety Glazing Systems for Road Vehicles,'' or by the
British Standards Institution (BSI), BSI AU 209, ``Vehicle Security,''
which provide glazing intrusion resistance requirements from external
impact (as opposed to ejection mitigation). These industry standards
specify that after testing there must not be separation within the
glazing or between the glazing and vehicle body that would allow for
passage of a 40 mm diameter sphere. The EPGAA stated that it is
necessary to ``specify a maximum opening after impact in addition to an
excursion limit to adequately address the remaining gaps leading to
partial ejections.'' It goes on to state that ``NHTSA currently
requires gap quantification limitation for windshields to resist
occupant ejection in FMVSS [No.] 205, which mandates compliance with
ANSI/SAE Z26.1 where glazing tears are measured and limited after
impact.'' In contrast, Batzer and Ziejewski indicated that the 100 mm
displacement appeared appropriate.

    Advocates suggested that the proposed displacement limit be reduced
by 50 percent, to 50 mm. It stated that a 100 mm displacement limit
``allows enough excursion to permit serious injuries and deaths outside
the vehicles. The 4-inch limit also devalues the major contribution
that advanced glazing can make to reduce the chances of occupant
ejections, including excessive occupant excursion outside side
windows.''
3. Agency Response
    NHTSA does not agree with the requested changes to the displacement
measurement method from the vehicle manufacturers and TRW, which would
all effectively increase the allowable displacement. We also disagree
with the additional post-impact gap measurement suggested by the
glazing suppliers. We also do not concur with the requests of some
commenters to increase the displacement limit, and of some to reduce
it. We believe that the 100 mm limit strikes the appropriate balance
between stringency and practicability. We address the issue of
stringency and practicability further in a later section on the time
delay of the impacts and impactor velocity.
Suggested Methods Would Increase the Displacement Limit
    We do not believe that the methods suggested by the commenters
provide a better method of measuring the performance of the ejection
countermeasure. No data was presented to support why the suggested
methods are preferable to the method proposed in the NPRM.
    In the NPRM and the technical analysis supporting the NPRM, the
agency estimated that the GM measurement method allowed about 6 percent
more displacement than the proposed method of measurement. Below we
analyze the displacement measurement methods requested by the
commenters and compare the associated performance limits of the
respective methods to the performance limit discussed in the NPRM. For
this comparison, we used a graphical representation of a two
dimensional lateral cross-section of the headform contact with the side
window. For convenience, we used an approximation of the headform
profile rather than the exact cubic equation prescribed in the NPRM.
The vehicle cross-section included the window as well as the structure
in its vicinity.
    Figure 6 shows how the 100 mm displacement put forward in the NPRM
is measured from the contact point of the headform at the A2 target
point with the side window glazing. In this example, the lateral cross-
section A-A of the glazing is represented by a 15 degree arc segment
having a 201 cm radius, with the base of the arc oriented approximately
7 degrees from the vertical.
[GRAPHIC] [TIFF OMITTED] TR19JA11.007

    Figure 7 shows the displacement measurement methods that Honda and
the Alliance recommended in their comments. In the Honda method, the
lateral cross-section of the glazing is projected 100 mm along the
normal line at the point of contact of the headform. Using the Honda
method, the headform's horizontal displacement at the A2 target is 101
mm from the NPRM zero displacement point. The Alliance-recommended
measurement method defines a line tangent to the side of the vehicle at
the window opening as the zero excursion plane. The maximum excursion
plane is defined by translating the excursion plane 150 mm laterally.
Using the Alliance method, the headform's horizontal displacement at
the A2 target is 161 mm from the NPRM zero displacement point. This 161
mm value is the sum of the 11 mm distance between the contact point
with the window and the excursion plane ([Delta] excursion plane) and
the 150 mm

additional displacement to the maximum excursion plane.\73\
---------------------------------------------------------------------------

    \73\ In doing this analysis, we have assumed that the point of
contact with the glazing is along the centerline of the headform. If
we did not, the difference between the NPRM method and the Alliance
and AIAM proposals would be even greater.
[GRAPHIC] [TIFF OMITTED] TR19JA11.008

    AIAM also recommended a displacement measurement method similar to
the Alliance method in that an excursion plane is located tangent to
the side of the vehicle window opening. However, the maximum excursion
plane is defined by translating the excursion plane by 100 mm along a
line normal to the excursion plane rather than 150 mm laterally.
    Because of the similarities between the Alliance and AIAM methods,
once the angle of the excursion plane is known, a simple mathematical
relationship can be used to calculate the AIAM displacement limit with
respect to the NPRM measurement method from the limit determined by the
Alliance method. From Figure 7 we see that the excursion angle is 17
degrees from the vertical. Thus, the horizontal translation of the AIAM
maximum excursion plane is 105 mm = 100/cos(17 deg.). The total AIAM
displacement allowance from the headform when in contact with the
window plane is the sum of the [Delta] Excursion Plane (11 mm) plus the
horizontal translation of the excursion plane (105 mm), resulting in a
value of 116 mm at target A2.
    The displacement measurement methods suggested by Honda, the
Alliance, and AIAM are all more sensitive to the particular target
location, the curvature and angle of the window, as well as the profile
of the vehicle structure around the window opening, than the NPRM
method. Figure 8 shows the NPRM displacement measurement at target A4
for a side window having twice the base angle (13 degrees) as the
previous example. The window curvature remains the same. Figure 9 shows
a graphical determination of displacement measurements for Honda (109
mm) and the Alliance (156 mm) at A4. Using the mathematical
transformation described above, we calculate the AIAM value (114 mm).

[GRAPHIC] [TIFF OMITTED] TR19JA11.009

[GRAPHIC] [TIFF OMITTED] TR19JA11.010

    The same exercise was performed for target position A2 with a 13
degree window and for target position A4 with a 7 degree window. Figure
10 shows the displacement limits calculated for the three commenters'
methods at target positions A2 and A4 with a 7 and 13 degree window,
subtracted from the 100 mm limit in the NPRM. The Honda

method provides the smallest differential with the NPRM method (1 to 9
mm), the Alliance method provides the largest (55 to 61 mm). Again, the
results will vary for other target locations and window/vehicle
geometries. However, there does not appear to be a situation where any
of the suggested methods will result in a lateral displacement limit of
less than 100 mm. That is, each suggested method would reduce the
stringency of the test by permitting the openings to be greater than
100 mm. As explained in the section below, this we cannot accept.
[GRAPHIC] [TIFF OMITTED] TR19JA11.011

    TRW requested allowing the zero reference plane to move with the
door frame. We are declining this request. It is unclear to us why
allowing the reference plane to move in the manner suggested is
preferable from a safety standpoint than simply maintaining the
position of the zero plane with respect to ground. The latter (NPRM)
method is preferable because the door frame provides a reaction surface
for the curtain air bags or advanced glazing. The door frame is part of
the system designed to retain the occupant in the vehicle. If the zero
reference plane is tied to movement of the door frame, a weak door
frame could render the displacement limit meaningless. For example,
under the TRW method, a vehicle that allows an impactor displacement of
150 mm with 50 mm of door deflection would be considered compliant, as
would a vehicle that allows an impactor displacement of 100 mm with 0
mm of door deflection.
    Further, the TRW suggestion would also add a significant amount of
complexity to the testing. There would need to be a determination as to
the sufficient number of measurement locations on the door and how the
agency would assess movement of the door frame. The suggestion requires
further study to properly integrate it into the test procedure and we
are unable to conclude that use of our resources to pursue the matter
would be warranted.
Unrealistic Assumptions
    The methods of measurement suggested by the Alliance, AIAM and
Honda are dependent on assumptions about the performance of the vehicle
that may not be realistic. The Alliance and AIAM methods are very
similar. Both these methods use a tangent to the side of the vehicle
(zero excursion plane), translated some distance, as the limit of
displacement (maximum excursion plane). The assumption apparently is
that occupant excursions within this zone will be protected.
    We do not agree with this assumption. For example, if vehicle A's
exterior skin protrudes farther outboard than vehicle B's, but A's
protruding exterior skin consists of only sheet metal or plastic or

some like material that provides little if any crush resistance, we do
not agree that A's maximum excursion plane should be farther outboard
at the bottom of the window opening than B's. More displacement of the
headform would be permitted for vehicle A even though in a real-world
crash, A's exterior skin could be easily leveled. Since the
countermeasure of A would be permitted to allow more headform
displacement outside of the window plane than that of B, the suggested
approach would provide A's occupants less minimal protection in a
rollover or side impact than the NPRM approach.
    Relatedly, when the excursion plane is derived from the undeformed
vehicle structure, if the roof structure has significant lateral
deformation after impact, the original excursion plane may have very
little relevance to occupant protection.
    With Honda's method, it seems there is an underlying assumption
that if ground contact occurs with the vehicle rotated 90 degrees, the
door structure will be the initial point of contact, so that targets
near the upper part of the glazing on a vehicle with a highly inclined/
curved glazing could be permitted to displace farther than targets at
the center. Under this method, the greater the inclination and/or
curvature of the glazing in the lateral plane, the more displacement is
allowed compared to the NPRM's approach (9 percent more at A4 with the
13 degree glazing). A vehicle with a more highly inclined glazing would
be allowed more headform displacement at the top and bottom of the
window compared to the NPRM. Given the unpredictable nature of rollover
crashes, we cannot agree with this assumption. A vehicle might be
rotated greater than 90 degrees during ground contact, resulting in
initial contact near the upper glazing. Thus, to allow more
displacement at the top of the glazing relative to the initial glazing
position does not seem warranted.
Adding Complexity
    The measurement methods suggested by the Alliance, AIAM, Honda and
TRW are more complicated to implement than the method proposed by the
agency. The NPRM's method of measuring displacement is actually very
simple and straightforward. The point of zero displacement is simply
the contact point with the side window glazing. From there, it is only
necessary to keep track of how far the linear impactor translates along
its axis of motion. No digitization or CAD techniques are required. To
find the zero displacement point for the Alliance or AIAM method, one
must hold a relatively thin straight edge in a lateral vehicle plane,
aligned with the target center, against the outside of the vehicle.
Headform contact with this straight edge defines the point of zero
displacement. This can be done by digitizing the exterior of the
vehicle. However, it is somewhat more onerous than the NPRM method. The
Honda method is just as simple as the NPRM method in finding the point
of zero displacement, but after that, we believe the method would
require a digitization of the glazing. This digitized glazing would
then need to be manipulated in a CAD program to determine the allowable
displacement. The complexity of the TRW method has been discussed
above.
Increasing the Displacement Limit
    The agency is declining the requests to increase the allowable
displacement limit.
    The Alliance and Volvo believe the limit should not be based on the
size of a child's head and the impact energy of an adult male. (In
contrast, Honda commented that basing the requirement on the size of a
child's head was appropriate.) We disagree with the Alliance and Volvo
on this point. It is reasonable for the agency to adopt a displacement
limit based on the anthropometry of a child since the standard is
intended to mitigate ejection of all sizes of occupants, not just the
mid-size male. It is possible for a child occupant to interact with an
ejection mitigation countermeasure with relatively high impact energy
if a large portion of their mass is considered. For example, an average
5-year-old child weighs about 18 kg (the same mass as the linear
impactor). Due to the size of this child relative to a window opening,
it would be much easier for their entire body mass to interact with the
window opening than it would be for an adult. Also, the ejection
mitigation countermeasure could be double-loaded by more than one
occupant simultaneously during the rollover event, e.g., a child in the
rear seat and the driver in the front seat or two unbelted occupants in
the same row. The 100 mm limit reduces the likelihood that openings
will form during the rollover that are large enough to pass the head or
other body part of a child or an adult.
    The principle underlying the 100 mm displacement limit is to ensure
that the entire window opening is covered, and covered by a
countermeasure resilient enough to withstand the forces that could be
imposed on it in a rollover without forming gaps or openings.\74\ We
chose a 100 mm displacement limit as a reasonable and objective measure
of acceptable performance, taking into account the practicability of
meeting the displacement limit, safety need, and the SAFETEA-LU goal of
a standard that reduces complete and partial ejections of vehicle
occupants. We adopt a displacement limit that will ensure that the
countermeasure covering the entire window is wide enough and strong
enough to mitigate ejection of a child's head, limb or body, or those
of an adult, in the chaotic and unpredictable phases of a rollover.
---------------------------------------------------------------------------

    \74\ 74 FR 63193.
---------------------------------------------------------------------------

    IIHS believed that the NPRM selection of 100 mm displacement,
partially based on other standards (FMVSS Nos. 206 and 217) and
building codes, may be unreasonable. It noted that the vehicle testing
reported in the NPRM did not show any that passed all the target points
at 100 mm of displacement even though the field performance of these
vehicles may be acceptable. IIHS stated that if the displacement
requirement is too stringent it will lead manufacturers to make their
air bags too stiff, with unknown consequences from this increased
stiffness.
    We understand the merits of having extensive field data that
correlates the performance in the proposed test against ejection
mitigation in the field. At the time of the NPRM development, there
were very few rollover curtain-equipped vehicles in the available field
data and the vehicles then-tested by the agency were not designed to
have full window coverage as the NPRM requirements contemplated. Now
more field data is available to us, and we have tested many more
vehicles some of which have been designed to have extensive window
opening coverage. However, the data set is still insufficient to
correlate various displacement values and field performance.
    Nonetheless, we do not accept IIHS's argument that the 100 mm value
may be unreasonable because the value is used in FMVSS No. 206 and 217
and in the architectural code. These other standards and the
architectural code referenced by the agency have basically the same
purpose: retaining occupants, including children, in a vehicle in a
crash event, or retaining children behind a barrier (railing). These
precedents are supportive of the selected value. They were developed
taking into consideration the size of children's heads and limbs and
the ease or difficulty with which the parts can fit through openings.
If the window opening countermeasure can limit the

opening to 100 mm when impacted by the headform at the prescribed
velocities, the countermeasure is more likely to be able to restrict
the opening as needed when impacted by a lower mass at the same or
higher velocity, or the same or larger mass at a lower velocity.
Requests to Decrease Displacement Limit
    Advocates suggested that the proposed displacement limit be reduced
by 50 percent to 50 mm. It believed that such a stringent requirement
will ``ensure dramatic reductions in occupant ejection, including
partial ejection * * *.'' It stated further that the proposed 100 mm
value ``devalues the major contribution that advanced glazing can
make'' and that more lives would be saved by ``a standard that
effectively would encourage the use of advanced glazing in combination
with air curtains * * *.'' \75\ The suggestion to reduce the
displacement limit was made by other commenters as well, including
glazing manufacturers.
---------------------------------------------------------------------------

    \75\ NHTSA-2009-0183-0022, p. 3.
---------------------------------------------------------------------------

    NHTSA does not believe that the level of stringency requested by
Advocates and others is warranted. We believe that the 100 mm limit
will be highly effective in the reduction of both complete and partial
ejections. Certainly, ejections will continue in situations where the
severity of the crash and resulting occupant energy will overwhelm the
capacity of the countermeasure. However, the 100 mm limit strikes the
appropriate balance between stringency and practicability.
    There is no available data that can correlate various displacement
values with field performance at this time. We cannot conclude that
reducing the displacement limit by 50 percent will reduce ejection or
side impact fatalities and injuries by a corresponding amount. The
commenters did not provide data on this issue. On the other hand, we
can estimate possible costs of indirectly requiring advanced glazing to
be installed at side windows to meet a 50 mm displacement limit. In the
FRIA, we estimated that the incremental difference in costs for going
from tempered glass to laminated advanced glazing for a standard size
side window in the first or row is $15. Thus, for a two row vehicle the
total incremental cost would be $60. In addition, we believe that any
costs associated with advanced glazing must be combined with the
curtain bag incremental cost since a system with movable advanced
glazing alone would not be able to perform to the level required for
this standard. In comparison, the agency has determined that
incremental cost of meeting the final rule with only curtain air bags
will be $31 dollars per vehicle. The cost per equivalent fatality of a
system comprised of a partial curtain in combination with laminated
glazing was twice that of a system utilizing only a curtain.
Requests To Add Another Requirement
    Many glazing manufacturers were in favor of applying an additional
post-impact requirement in which a 40 mm sphere is used to determine
the size of any remaining gaps. According to the commenters, this
requirement would be intended to eliminate gaps that can exacerbate
partial ejections. It is our interpretation of the comments that this
test is to be applied to all vehicles, i.e., those using a combination
of advanced glazing and side curtain air bags to meet the standard, and
those using only side curtain air bags.
    We do not agree with this suggestion. First, the requirement is not
appropriate for vehicles with only side curtain air bags, given that
there is a time dependence associated with a curtain's ejection
mitigation performance. Once deployed, the pressure in the air bag
continuously decreases. The 16 km/h test is done at 6 seconds to assure
that the pressure does not decrease too quickly. It does not seem that
the 40 mm gap test could be done after the 6-second impact, in any
timeframe which is related to rollover and side impact ejections.
Second, there is no shown safety need for the requirement. We cannot
show that ejections that would not be prevented by the primary 100-mm
displacement requirement would be prevented by a secondary 40-mm
requirement. Third, it would seem that the 40-mm requirement would
indirectly require installation of advanced glazing. As discussed
above, the costs associated with advanced glazing installations at the
side windows covered by this standard are substantial in comparison to
a system only utilizing rollover curtains. For these reasons, the
agency does not accept this suggestion.

c. Times and Speed at Which the Headform Impacts the Countermeasure

    We have determined that there is a need for a relatively high speed
impact shortly after countermeasure deployment and a lower speed impact
late in the deployment. The two time delays correspond to relatively
early and late times in a rollover event.\76\ The first impact is at 20
km/h, and at 1.5 seconds after countermeasure deployment (1.5 second
time delay). (The 20 km/h speed is reduced from the NPRM's proposal of
24 km/h; the rationale for which is discussed later in this preamble.)
The second is a 16 km/h impact initiated 6 seconds after deployment.
---------------------------------------------------------------------------

    \76\ Each impact takes place on a test specimen (e.g., a
curtain) that was not previously subject to an impact test.
---------------------------------------------------------------------------

1. Time Delay (Ejections Can Occur Both Early and Late in the Rollover
Event)
i. NPRM
    Two impacts were proposed because ejections can occur both early
and late in the rollover event. In the advanced glazing program, NHTSA
performed a series of simulations to recreate three NASS-investigated
rollover crashes with ejected occupants.\77\ The vehicles were a MY
1991 Toyota pickup, a MY 1986 Toyota Corolla and a MY 1985 Volkswagen
Jetta.\78\ Vehicle handling simulation software \79\ reconstructed the
vehicle motion up to the point where the vehicle started to roll. The
linear and angular velocity at the end of the vehicle handling
simulation was then used as input to a MADYMO \80\ lumped parameter
model of the vehicle to compute its complete rollover motion. The
motion of the vehicle obtained from the MADYMO vehicle model was used
as input to a MADYMO occupant simulation. Head and torso velocities of
a Hybrid III 50th percentile male driver dummy were calculated for the
three rollover simulations.
---------------------------------------------------------------------------

    \77\ ``Ejection Mitigation Using Advanced Glazings: A Status
Report,'' November 1995, Docket NHTSA-1996-1782-3. Pg. 6-1.
    \78\ The circumstances of the Toyota pickup rollover was that
the vehicle was traveling at 96 km/h and went into a sharp turn and
yaw, which resulted in a rollover. In the case of the Corolla, it
was also traveling 96 km/h on a gravel road. The vehicle went out of
control and left the road, resulting in roll initiation. The
Volkswagen was traveling at 88 km/h when the driver fell asleep and
the vehicle left the road. It struck a rock embankment and rolled
over.
    \79\ VDANL software user's manual V2.34, STI, 1992.
    \80\ MADYMO user's manual V5.1, TNO, 1994.
---------------------------------------------------------------------------

    Table 30 shows the simulation resultant head velocity through the
open window at the time of ejection. As indicated in the table, for the
unrestrained simulations, the occupant of the pickup was completely
ejected early (1st quarter-turn for Toyota truck) while the occupants
of the other vehicles were ejected late (last quarter-turn for Corolla
and Jetta) in the rollover event.

    Table 30--Head and Torso Velocities of a Hybrid III 50th Percentile Male Dummy in 3 Rollover Simulations
----------------------------------------------------------------------------------------------------------------
                                            \1/4\ Turns                      Head to      Head to      Torso to
           Vehicle             Vehicle \1/  at complete    Restraint use   opening (km/ glazing (km/ glazing (km/
                                 4\ turns     ejection                          h)           h)           h)
----------------------------------------------------------------------------------------------------------------
Toyota PU....................           12  ...........  Yes.............           20           20            7
                               ...........            1  No..............            5           20           16
Toyota Corolla (86)..........            6  ...........  Yes.............           15           15           11
                               ...........            6  No..............           13           13           10
Volkswagen Jetta (85)........            4  ...........  Yes.............           14           14           10
                               ...........            4  No..............           22           18           16
----------------------------------------------------------------------------------------------------------------

    The agency also considered other data indicating that very early
occupant contact with the window area is possible in rollover crashes.
Table 31 gives information on 30 rollover tests the agency performed
from the mid-1980s to the mid-1990s. This data set included Rollover
Test Device (RTD) tests, 208 Dolly tests, guardrail tests and pole
tests.\81\ A film analysis of dummy motion within the vehicles showed
that, excluding a pole impact test, occupant contact with the window
opening and surrounding area first occurred between 0.16 and 0.88
seconds after the event began.\82\ We note, however, that the majority
of these dummies were belted, which means they would be most
representative of potential partial ejections. In addition, where the
time of window breaking is known, most of these first contacts occurred
prior to the window breaking due to roof contact.
---------------------------------------------------------------------------

    \81\ These tests were done as part of a research program
evaluating full scale dynamic rollover test methods, occupant
kinematics, and vehicle responses. The RTD tests were similar to the
208 Dolly test except that the vehicle was initially 4 feet off of
the ground instead of 9 inches, and hydraulic cylinders were used to
push the vehicle from the cart and produce an initial roll rate. The
guardrail tests used a guardrail as a ramp to initiate a vehicle
roll. The pole tests rolled a vehicle into a pole. Twenty-four of
these were RTD tests on passenger cars, pickups and vans (the RTD
testing was not geared towards ejection testing since all of the
test dummies were belted), and four were 208 Dolly tests on Ford
Explorers. The test films are available at the National Crash
Analysis Center (NCAC) at George Washington University
(www.ncac.gwu.edu).
    \82\ ``Evaluation of Full Vehicle Rollover Films,'' 2008, Docket
NHTSA-2006-26467.

                                               Table 31--NHTSA Full Vehicle Rollover Testing Film Analysis
--------------------------------------------------------------------------------------------------------------------------------------------------------
                                                                                Tilt                Vehicle
  Test             Make                  Model             MY           Test type         angle    Roll axis  speed (km/    \1/4\    Total time
                                                                                (deg.)     (deg.)       h)        Turns       (sec)
--------------------------------------------------------------------------------------------------------------------------------------------------------
878...............  Honda...............  Accord..............         84  RTD.................         41         45       33.8         2          1.29
888...............  Chevrolet...........  Celebrity...........         82  RTD.................         41         45       37.0         4          3.58
920...............  Dodge...............  Omni................         79  RTD.................         41         45       37.0         2          0.96
939...............  Mercury.............  Zephyr..............         82  RTD.................         41         60       37.0         2          2.08
1255..............  Ford................  Bronco..............         88  RTD.................         30         45       37.0         2          1.17
1266..............  Dodge...............  Caravan.............         88  RTD.................         30         45       48.3         1          0.50
1267..............  Chevrolet...........  Pickup..............         88  RTD.................         30         45       48.3         4          2.58
1274..............  Nissan..............  Pickup..............         88  RTD.................         30         45       48.3         6          3.76
1289..............  Nissan..............  Pickup..............         89  RTD.................         30         45       48.3         2          0.83
1391..............  Dodge...............  Caravan.............         89  RTD.................         30         45       48.3         8          5.08
1392..............  Ford................  Bronco..............         89  RTD.................         30          0       48.3         8          3.60
1393..............  Nissan..............  Pickup..............         89  RTD.................         30          0       48.3         4          2.35
1394..............  Nissan..............  Pickup..............         89  RTD.................         30          0       48.3         4          1.33
1395..............  Pontiac.............  Grand Am............         89  RTD.................         30          0       48.3         2          1.54
1471..............  Dodge...............  Colt................         89  RTD.................         30         90       48.3         2          0.99
1520..............  Ford................  Ranger..............         88  RTD.................         30          0       48.3         2          0.75
1521..............  Dodge...............  Ram.................         88  RTD.................         30          0       48.3         4          1.42
1530..............  Dodge...............  Caravan.............         88  Guardrail...........         NA         NA       96.6         1        N/A
1531..............  Nissan..............  Pickup..............         88  Guardrail...........         NA         NA       96.6         4        N/A
1546..............  Plymouth............  Reliant.............         81  RTD.................         41         45       33.8         6          3.00
1851..............  Volvo...............  240.................         91  RTD.................         30          0       48.3         6          2.50
1852..............  Volvo...............  740.................         91  RTD.................         30          0       48.3         8          3.00
1925..............  Nissan..............  Pickup..............         90  RTD.................         30          0       48.3         8          3.04
1929..............  Nissan..............  Pickup..............         90  RTD.................         30          0       48.3         6          2.25
2141..............  Nissan..............  Pickup..............         90  RTD.................         30          0       48.3         8          4.25
2270..............  Nissan..............  Pickup..............         89  RTD.................         30          0       48.3         8          3.50
2514..............  Ford................  Explorer............         94  208.................         23          0       48.3        11          5.50
2553..............  Ford................  Explorer............         93  208.................         23          0       48.3        10        N/A
3012..............  Ford................  Explorer............         94  208.................         23          0       48.3        11        N/A
3635..............  Ford................  Explorer............         94  208.................         23          0       48.3        12          5.17
--------------------------------------------------------------------------------------------------------------------------------------------------------
Analysis of 5+ \1/4\ turn Tests:
    Average..........................................................................................................       47.2         8.3        3.7
    Maximum..........................................................................................................       96.6        12          5.5
    Average +2 standard deviations...................................................................................       55.2        12.3        5.8
--------------------------------------------------------------------------------------------------------------------------------------------------------

    The agency proposed that the ejection mitigation countermeasure be