Unfortunately, a question remains about whether the NHTSA proposed
method and criterion is, by itself, adequate to limit long single
glances.\207\
---------------------------------------------------------------------------

    \207\ Ibid, p. 4.

    Professor Young presents hypothetical data to create a scenario,
demonstrating that the combined effects of the three eye glance
criteria proposed by NHTSA (mean glance duration, TEORT, and proportion
of long glances) allow for the possibility of single glances as long as
---------------------------------------------------------------------------
3-6 seconds in duration.

    If the criteria above are applied to hypothetical data, it
becomes apparent that, in theory, tasks with 7 to 10 average glances
of 1 sec each could have one single glance as long as 3-6 sec and
still meet NHTSA glance criteria.\208\
---------------------------------------------------------------------------

    \208\ Ibid.

    Although the inclusion of a long-glance criterion is positive,
Professor Young argues that because of the hypothesized connection
between long glances and attention shifts, a separate criterion is
---------------------------------------------------------------------------
needed:

    Simply tightening the single glance duration limit to be lower
than the 15% criterion is not recommended because it does not
address the underlying problem of the attentional shifts that give
rise to long single glance durations. Instead, it is recommended
that an additional event detection and response test (above and
beyond glance measures) is required to evaluate the effect that a
device or task has on the underlying attentional processes which
contribute to controlling long single glances.\209\
---------------------------------------------------------------------------

    \209\ Ibid, p. 12.

    To summarize, Professor Young is making the following arguments:
    1. Long-duration glances are implicated in crash causation.
    2. Long-duration glances are more likely to reflect attentional
processing than shorter-duration glances.
    3. Glance-based metrics do not provide all the information
necessary to determine where the driver's attention is directed.
    4. Proposed NHTSA criteria still permit occurrence of single long-
duration glances.
    5. An event-detection metric, which requires responses to targets,
provides better information about where a driver's attention is
directed than any of the glance-based metrics.
    Evidence of Professor Young's influence is evident in comments
received from the Motor & Equipment Manufacturers Association.

    He [Professor Young] notes that the longest glance time--not the
total glance time or the average glance time--plays a different role
in ``event detection' and, thus, requires more coverage in the
guidelines. * * * MEMA urges the agency to consider event detection
in the applicable performance tests.\210\
---------------------------------------------------------------------------

    \210\ Comments received from Motor & Equipment Manufacturers
Association, p. 3. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0091.
---------------------------------------------------------------------------

b. NHTSA's Response
    NHTSA shares these commenters' concerns about the negative effects
of long eye glances away from the forward road scene on driving safety.
Accordingly, NHTSA included a long eye glance-based task acceptability
criterion to its Driver Distraction Guidelines not present in the
Alliance Guidelines: that, for at least 21 of 24 test participants, no
more than 15 percent (rounded up) of the total number of eye glances
away from the forward road scene have durations of greater than 2.0
seconds while performing a task one time. Professor Young points out
\211\ that a task can have one single long glance (in the 3 to 6 second
range) and still meet all of NHTSA's task acceptance criteria. This is
correct; NHTSA agrees that our current long eye glance criterion does
not completely resolve this issue. While we think that it is a step in
the right direction, secondary tasks that involve short term levels of
high cognitive distraction are not screened out by our current task
acceptance criteria.
---------------------------------------------------------------------------

    \211\ Comments received from Professor Richard A. Young,
Attachment 2, p. 4. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0106.
---------------------------------------------------------------------------

    Some commenters thought that long eye glances away from the forward
road scene might have a greater effect on driving safety than does a
longer TEORT. NHTSA does not know whether this is the case but suspects
that both long eye glances away from the forward road scene and a
longer TEORT have negative effects on driving safety. Fortunately,
NHTSA does not have to resolve this question since our task acceptance
tests can (and do) have multiple acceptance criteria.
6. Eye Glance Measurement Issues
a. Summary of Comments
    Two comments were received addressing procedural details of the
collection and use of eye glance data for determining the total eyes-
off-road time. Comments provided by the Swedish Road and Transport
Research Institute (VTI) addressed the precision and

repeatability of recording gaze direction, recommending that a well-
calibrated eye tracker would be preferable to manual coding of gaze
direction from face video:

    To ensure sufficient accuracy, precision, and repeatability of
an eye tracker, it is not sufficient to use manual coding of gaze
direction. A more objective way of doing this is to use a number of
fixed gaze targets (for example on the simulation screen) that the
driver is instructed to look at. It is then an easy task to measure
the deviation between the location of the gaze target and the eye
trackers estimate of the drivers gaze. This procedure is commonly
used in head mounted eye trackers, and could easily be adopted for
remote eye trackers as well. Crisp thresholds for accuracy and
precision could then be established instead of the soft boundaries
that follow from manual coding.\212\
---------------------------------------------------------------------------

    \212\ Comments received from the Swedish Road and Transport
Research Institute, pp. 3-4. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 056.

    The following comment from Volvo was directed at the level of
effort required to accomplish manual reduction of video data to obtain
---------------------------------------------------------------------------
glance information required by the guideline metrics:

    * * * reduction of eye glance location from full motion video is
very time consuming, especially considering the vast number of tests
that would need to be conducted if following the recommended test
procedures.\213\
---------------------------------------------------------------------------

    \213\ Comments received from Volvo Car Corporation, p. 5.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 108.
---------------------------------------------------------------------------

b. NHTSA's Response
    While NHTSA shares many of VTI's concerns about the accuracy of
manual coding of gaze direction from face video, we also have concerns
about eye tracker accuracy. NHTSA has had extensive experience with eye
trackers during driver distraction testing performed by its Vehicle
Research and Test Center (VRTC) over the last five years.
Unfortunately, VRTC's work has found numerous eye tracker accuracy
issues.
    Therefore, NHTSA is not prepared to recommend the use of an eye
tracker as the sole method for eye glance data reduction. In VRTC's
experience, both methods of eye glance data reduction are resource
intensive and have reasonable, but not excellent, accuracy. For this
reason, NHTSA has included both eye tracker and manual coding of gaze
direction from face video as acceptable methods for eye glance data
reduction in its Guidelines.
    NHTSA shares many of Volvo's concerns about the resources need to
reduce eye glance data either with an eye tracker or through manual
coding of gaze direction from face video. This is one reason that we
have included Occlusion testing in NHTSA's list of recommended task
acceptance test protocols. In our experience, Occlusion testing
provides comparable results but uses fewer resources.
7. Occlusion Acceptance Test Criteria Issues
a. Summary of Comments
    Comments were provided about the Occlusion Task Acceptance Test
protocol contained in the proposed NHTSA Guidelines. Some comments
raised more general concerns about the method, while others addressed
the specific criterion value proposed by NHTSA.
    Chrysler presented comments that were critical of the occlusion
method. After acknowledging some benefits of occlusion, including the
fact that no simulator is required, the relatively low effort and cost,
and harmonization with the Alliance Guidelines, Chrysler identified
several problems with the procedure, which were discovered in their own
use of the procedure:

    * * * the occlusion apparatus forcibly restricts single glance
duration which does not reflect real world conditions. This was
noted by the participant's lack of peripheral vision during the
occlusion intervals. Because the individual is temporarily blinded
when the shutters on the goggles close, there is a tendency for some
individuals to lose kinesthetic awareness. The individual's body and
hands have tendency to drift while the shutters are closed,
something that doesn't normally happen during actual driving. For
these reasons, the OCC method has not been and continues to not be
preferred by Chrysler.\214\
---------------------------------------------------------------------------

    \214\ Comments received from Chrysler Group LLC, p. 5. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0095.

    Volkswagen Group of America (VW) provided detailed comments on the
proposed 9-second Total Shutter Open Time (TSOT) criterion value,
referring extensively to the results of a report \215\ released by
NHTSA in support of the guidelines proposal:
---------------------------------------------------------------------------

    \215\ Ranney, T.A., Baldwin, G.H.S., Smith, L.A., Martin, J. &
Mazzae, E.N. Driver Behavior During Visual-Manual Secondary Task
Performance: Occlusion Method Versus Simulated Driving. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0077.

    The report found that the 9 second TSOT criterion was too
stringent, in that both radio tuning and destination entry did not
meet the criterion. The 9 second TSOT criterion was derived from the
12-second TEORT [Total Eyes-Off-Road Time] criterion established
based on testing in another study. * * * NHTSA refers to the assumed
3:4 relationship between TSOT and TEORT as the ``75 percent field
factor.'' However, this assumed ``field factor'' proves to be
unsupported by the data in the subject report which finds that both
a regression analysis and a comparison of mean values showed that
the relationship between TSOT and TEORT was near 1:1. In spite of
this contrary finding, and the fact that the Prius radio tuning task
did not meet the NHTSA criterion of 9 seconds TSOT, NHTSA
nevertheless put forward a final acceptance criteria of 9 seconds
for TSOT.\216\
---------------------------------------------------------------------------

    \216\ Comments received from Volkswagen Group of America,
Attachment, p. 4. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0101.

    Volkswagen was critical of a re-analysis of TSOT data that was
---------------------------------------------------------------------------
described in the above-mentioned technical report:

    * * * the analysis of TSOT data was redone using a subset of the
data collected, re-stratified into different age groupings, and
discarding the older test subjects. Only after discarding the data
from the older subjects was it possible to claim support for the
finding that the Prius radio tuning task met the 9-second TSOT
criterion, while the destination entry task did not. This type of
data manipulation to support a desired result is not consistent with
sound scientific or engineering practices. We also note that the
contradicted assumption that there is a 3:4 relationship between
TSOT and TEORT has yet to be addressed by NHTSA.\217\
---------------------------------------------------------------------------

    \217\ Ibid.

    Volkswagen also cited the findings of a separate study presenting
results of a survey of experts on various issues relating to the
---------------------------------------------------------------------------
guidelines proposal. They cite the following finding from that report:

    The experts agree that the 15 seconds total shutter open time
was not excessive and seemed a good value to use.\218\
---------------------------------------------------------------------------

    \218\ Ibid, p. 2.
---------------------------------------------------------------------------

b. NHTSA's Response
    Initially, NHTSA shared Chrysler's concerns about occlusion
testing. However, based on NHTSA experience using this protocol in its
own research and a careful review of the occlusion literature, we think
that these concerns are more theoretical than real. Occlusion testing
has substantial advantages: no driving simulator is required,
relatively low effort is involved in implementing the protocol, the
protocol is easy for test participants to comply with, testing cost is
lower than other available methods such as driving simulation based
methods, and results are repeatable. While NHTSA has learned that many
manufacturers currently perform occlusion testing to support their
product development research, NHTSA notes that groups who do not prefer
the occlusion method are free to use the Eye Glance Measurement

Using Driving Simulator Testing protocol to assess their products'
conformance to the NHTSA Guidelines.
    In response to Volkswagen's comments critical of NHTSA's Occlusion
Testing acceptability criterion, NHTSA revisited its basis for the
specific value proposed. NHTSA agrees with Volkswagen that its 2011
study did not support a 75 percent field factor relating occlusion
testing TSOT to TEORT for driving glances. The 2011 NHTSA study showed,
both through regression analysis and a comparison of mean values that
the relationship between TSOT and TEORT was near 1:1.
    In addition to the 2011 NHTSA study, other sources of information
consulted in determining the Occlusion Testing criterion included:
     Occlusion testing theory: assumes that every time a driver
looks away from the forward roadway (for occlusion testing, each such
eye glance is assumed to be 2.0-seconds long), the first approximately
0.50 seconds is spent transitioning the driver's eyes from the roadway
to the object being looked at.\219\ As a result, only 1.5 seconds of a
2.0-second eye glance are actually focused on the device being used.
---------------------------------------------------------------------------

    \219\ Perez, M., Hulse, M., and Angell, L., ``Support for NHTSA
Visual-Manual Guidelines: Expert Review of the Visual Occlusion
Method and How It Compares to Driver Eye Glance Behavior,'' p. 12,
DOT HS number not yet available, April 2012, accessible at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0075.
---------------------------------------------------------------------------

     ISO Standard 16673:2007 specifies an occlusion vision
interval (shutter open time) of 1.5 seconds.
    [cir] Based on occlusion testing theory that the 1.5-second shutter
open time is equivalent to an off-road glance duration of 2.0 seconds,
this would give a ratio of 0.75 (i.e., 1.5/2.0 = 0.75). Applying this
ratio to the TSOT/TEORT relationship results in a field factor of 75
percent.
     JAMA Guidelines: These Guidelines specify a maximum TSOT
value of 7.5 seconds and a maximum TEORT value of 8 seconds.
    [cir] These values give a TSOT/TEORT ratio of 0.8875.
     Hashimoto and Atsumi (2001), cited by the Alliance in
explaining their basis for an occlusion TSOT criterion, found that a
TEORT value (they refer to as ``TGT'' or total glance time) of 8
seconds was equivalent to a TSOT value of 7.1 s.
    [cir] These values give a TSOT/TEORT ratio of 0.9375.
    These sources suggest a TSOT to TEORT ratio ranging from 0.75 to 1.
In the proposed NHTSA Guidelines, NHTSA relied on occlusion testing
theory and ISO 16673:(2007) for the 75 percent field factor.
Accordingly, NHTSA determined an initial occlusion TSOT criterion of 9
seconds based on the driving glance TEORT criterion of 12 seconds.
    Since publication of the proposed NHTSA Guidelines, additional
research has found the TSOT/TEORT ratio to be closer to 1.0. In
addition to the April 2012 research report cited by Volkswagen,
recently completed NHTSA-sponsored research conducted by the University
of Washington and University of Wisconsin \220\ directly compared
secondary tasks using both driving simulator and occlusion protocols
and found that use of a 12-second criterion for occlusion TSOT provided
task acceptability results that were more consistent with results based
on a 12-second TEORT criterion for driving glances. Consistency of the
outcomes of these two protocols is important, since the NHTSA
Guidelines specify both of these protocols as options for assessing
conformance. Given that two research studies now cast doubt on the
equivalency of the originally proposed 9-second occlusion TSOT
criterion value with the 12-second TEORT for driving glances, NHTSA
believes that reconsideration of the TSOT criterion is warranted. Based
on the results of the two recent NHTSA research studies, NHTSA believes
that a TSOT criterion value of 12 seconds is more appropriate based on
the current state of knowledge in this area and anticipates that a 12-
second TSOT criterion will be more likely to provide comparable results
for task acceptability as compared to outcomes obtained using the Eye
Glance Measurement Using Driving Simulator Testing protocol and its
associated 12-second TEORT criterion.
---------------------------------------------------------------------------

    \220\ Boyle, L., Lee, J., Peng, Y., Ghazizadeh, M., Miller, E.,
Wu, Y., Huimin, X, and Chrysler, S., Text Reading and Text Input
Assessment in Support of the NHTSA Distraction Guidelines: Final
Report. DOT HS (number not yet available), October 2012, accessible
at www.regulations.gov, Docket NHTSA-2010-0053.
---------------------------------------------------------------------------

    Although the TSOT criterion has been amended, we are retaining the
1.5-second unoccluded viewing interval for occlusion testing. Given
NHTSA's research showing a 1:1 relationship between TSOT and TEORT, a
1.5-second viewing interval corresponds to 1.5 seconds of driving
simulator eyes-off-road time. The 1.5-second viewing interval duration
is specified in ISO 16673:2007 and is generally consistent with data
showing mean glance durations for radio tuning of between 0.9 and 1.4
seconds. Specifically, the Dingus \221\ and Rockwell \222\ studies
cited in the Alliance Guidelines indicated mean glance durations of
1.10 seconds and 1.44 seconds, respectively. NHTSA's studies indicated
radio tuning mean glance durations of 0.92 seconds \223\ and 1.00
second.\224\
---------------------------------------------------------------------------

    \221\ Dingus, T.A., Attentional Demand Evaluation for an
Automobile Moving-Map Navigation System, unpublished doctoral
dissertation, Virginia Polytechnic Institute and State University,
Blacksburg, VA, 1987.
    \222\ Rockwell, T.H., ``Spare Visual Capacity in Driving
Revisited: New Empirical Results for an Old Idea,'' in A. G. Gale et
al (editors), Vision in Vehicles II (pp. 317-324, Amsterdam:
Elsevier, 1988.
    \223\ Ranney, T.A., Baldwin, G.H.S., Mazzae, E.N., Martin, J.,
and Smith, L.A., ``Driver Behavior During Visual-Manual Secondary
Task Performance: Occlusion Method Versus Simulated Driving,'' NHTSA
Technical Report (in press), accessible at http://www.regulations.gov/#!documentDetail;D=NHTSA-2010-0053-0077, April
2012.
    \224\ Perez, M., Owens, J., Viita, D, Angell, L, Ranney, T.A.,
Baldwin, G.H.S., Parmer, E., Martin, J., Garrott, W.R., and Mazzae,
E.N., ``Summary of Radio Tuning Effects on Visual and Driving
Performance Measures--Simulator and Test Track Studies,'' NHTSA
Technical Report in press. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 0076, April 2012.
---------------------------------------------------------------------------

8. Suggestions To Include Effects of Workload Managers in Task
Acceptance Criteria
a. Summary of Comments
    Several commenters warned that the NHTSA Guidelines' requirements
could discourage the pursuit of new technological solutions to mitigate
driver distraction. Dr. Paul A. Green described the impending emergence
of workload managers and how the proposed guidelines could stifle
development:

    * * * the guidelines ignore the fact that what a driver can
safely do at any given time depends on the workload of the primary
task. On a straight section of an expressway, with no traffic
nearby, in daylight, in clear weather, a driver could conceivably do
a great deal more safely than the proposed guidelines allow.
However, in adverse conditions much less could be advisable. Thus,
if the primary task workload is known, information provided by a
workload manager, then what the driver can do becomes a set of
values for each situation, not a single set of values as they are
now. Vehicles with workload managers are currently being sold in
Europe, and there is interest in selling them in the U.S. Providing
this flexibility, recognizing what drivers can safely do, will make
the guidelines more sensible and acceptable to the driving
public.\225\

    \225\ Comments received from Dr. Paul Green, p. 7. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0052.
---------------------------------------------------------------------------

    Dr. Green continues, presenting his assessment of the implication
of failing to build flexibility into the guidelines:

    Inflexible guidelines discourage further development [of]
workload managers, a potentially lifesaving technology.\226\
---------------------------------------------------------------------------

    \226\ Ibid.

    While not addressing the issue of workload managers directly, the
---------------------------------------------------------------------------
Global Automakers described the same concern more broadly:

    * * * it is important to recognize the limitations of the
proposed Guidelines as a means of addressing the distraction matter
over the coming years, so that the Guidelines do not become an
impediment to technological innovation.\227\
---------------------------------------------------------------------------

    \227\ Comments received from Global Automakers. Attachment, p.
1. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0099.

    American Honda Motor Co. offered similar sentiments, referring to
the table in the proposal listing tasks for which the proposed
---------------------------------------------------------------------------
guidelines are intended to be applicable:

    The restrictions on the items listed in Table 9 may also hamper
research and development of other systems that can be beneficial to
safety. For example, automakers are beginning to bring the first
workload management systems to market, combining crash avoidance
systems with driver monitoring systems in a manner that offers the
ability to shed in-vehicle tasks while alerting the driver of the
need to focus their attention on the road. Future iterations of
workload management systems offer the promise of keeping the driver
engaged in the act of driving (helping to prevent disengagement that
can lead to drowsiness), while keeping the driver in the optimal
engagement range on the Yerkes-Dodson curve by discouraging
overstimulation to the point of distraction.\228\
---------------------------------------------------------------------------

    \228\ Comments received from American Honda Motor Co, Inc., p.
4. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 112.

    As suggested by Honda in the previous comment, workload managers
can potentially involve integration with other driver support systems.
Several comments referred to these systems and made recommendations on
how they should be accommodated in the proposed guidelines. Volvo Car
---------------------------------------------------------------------------
Corporation offered the following comment:

    Driver state assessment is critical in determining the attention
level of the driver and thus, critical to determining the potential
to perform further secondary non-driving-related tasks. The
development of driver state assessment systems is happening rapidly
and these systems in combination with driving control support
systems will have an impact in assisting drivers in managing the
real-time workload for each instant in time. The potential of these
systems for assisting drivers should be reflected in the test
procedures by allowing them to be active during the tests.\229\
---------------------------------------------------------------------------

    \229\ Comments received from Volvo Car Corporation, p. 5.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 108.

    Honda provided the following comment on driver assist and crash
---------------------------------------------------------------------------
avoidance systems:

    * * * automakers and suppliers are continuing to research and
develop advanced methods of displays that minimize distraction while
satisfying consumer demand for in-vehicle technologies and features.
One example of this is the rapid application of various driver
assist and crash avoidance technologies. These technologies may
offset some risks of driver distraction by monitoring roadways for
impending crashes and help focus the driver's attention to an
impending risk.\230\
---------------------------------------------------------------------------

    \230\ Comments received from American Honda Motor Co, Inc., p.
3. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 112.
---------------------------------------------------------------------------

b. NHTSA's Response
    Unfortunately, workload managers and/or other means for driver
state assessment have not yet reached a state of maturity where NHTSA
can determine how they should affect task acceptance criteria. NHTSA
cannot address workload management systems until research has further
progressed.
    As explained elsewhere in this notice, NHTSA's Driver Distraction
Guidelines will be revised as needed. The issuance with this notice of
the Phase 1 NHTSA Guidelines, while significant, is only one step in
the process of the development of NHTSA's Guidelines. The issuance of
Phases 2 and 3 of the Guidelines covering portable and aftermarket
devices, and auditory-vocal human-machine interfaces, respectively,
will provide additional guidance. NHTSA also intends to provide
Guideline Interpretation letters as needed.

Definition of Goal, Dependent Task, and Subtask

a. Summary of Comments
    Several comments requested clarification of the definition of the
goal of a task. Nissan North America offered the following comment:

    It is unclear how to apply this definition of `goal' for some
types of tasks. It can be easy to define the goal for tasks which
have a clear intention, such as destination entry. However, it is
difficult to quantify the ``driver's intended state'' for tasks
which may depend on the driver's ``mood'' or ``feelings,'' such as
browsing radio stations or audio inputs for a song the driver
likes.\231\
---------------------------------------------------------------------------

    \231\ Comments received from Nissan North America, Attachment,
p. 1. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 0096.

    Nissan asserts that the need for clarification of the definition of
---------------------------------------------------------------------------
a goal depends on the protocols selected for the final guidelines.

    Nissan believes clarification may be necessary depending on the
evaluation protocols provided for in the final guidelines. If the
final guidelines were limited to a single secondary task evaluation
method such as occlusion testing, the proposed definition of `goal'
would need to be adjusted to limit its scope to tasks which can be
evaluated using the recommended tests and criteria. Alternatively, a
general definition of `goal' is acceptable if a variety of
evaluation methods are provided.\232\
---------------------------------------------------------------------------

    \232\ Ibid, p. 2.

---------------------------------------------------------------------------
    Global Automakers provided the following comment:

    In some cases, it is difficult to determine the driver's
``goal.'' Tasks which depend on drivers' clear intention, such as
destination entry, are easier to determine. On the other hand, for
tasks which depend upon the driver's mood or feelings, such as
browsing audio, it can be difficult to determine precisely the
driver's goal.\233\
---------------------------------------------------------------------------

    \233\ Comments received from Global Automakers, Attachment, p.
4. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0099.

    Several comments were posted on the definition of a dependent task.
---------------------------------------------------------------------------
American Honda Motor Co., Inc. provided the following comment:

    Honda recommends that the definition and examples of dependent
tasks be enhanced to further clarify the distinction between a
dependent task and an independent task.\234\
---------------------------------------------------------------------------

    \234\ Comments received from American Honda Motor Co., Inc.,
Attachment, p. 7. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0112.

    Honda cites passages from the proposed Guidelines, which lead them
---------------------------------------------------------------------------
to the following conclusion:

    The aforementioned text indicates that dependent tasks are
contingent upon antecedent tasks and suggests a subtask could be
dependent upon other tasks or subtasks. Therefore, examples in which
dependent and independent tasks and subtasks are identified would be
helpful.\235\
---------------------------------------------------------------------------

    \235\ Ibid, p. 7.

    Honda provides the following example, for which they seek
---------------------------------------------------------------------------
clarification:

    As an example, we seek clarification on the task of listening to
the radio that appears to be comprised of the following:
    1. Turning the radio on (an independent subtask),
    2. Selecting AM or FM (a dependent subtask), and
    3. Selecting the frequency (a dependent subtask).
    Further clarification and examples would help us establish our
procedures, and help to assure that exercising the guidelines will
yield consistent results. To enhance our understanding of the
dependent and independent task definitions, additional

examples of each type of task would be helpful, as would
descriptions of how these definitions apply within specific
sequences of events. Examples should include the amount of time that
may pass before a subtask is considered an independent task and a
discussion of whether the rate or frequency at which a driver
performs a task should be taken into consideration.\236\
---------------------------------------------------------------------------

    \236\ Ibid, pp. 7-8.

    Nissan cited the definition of a subtask, which appeared in the
---------------------------------------------------------------------------
proposed guidelines and provided the following comment:

    This definition may be interpreted differently depending on the
task being evaluated and may be difficult to apply consistently. The
example NHTSA provided in the preamble of the notice which describes
how this definition would apply to entering a street name and street
number during destination entry helps clarify this definition,
however we request that NHTSA provide additional examples.\237\
---------------------------------------------------------------------------

    \237\ Comments received from Nissan North America, Attachment,
p. 2. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 0096.

    An almost identical comment was provided by Global Automakers.
b. NHTSA's Response
    Due to the large number of possible electronic device-related
secondary tasks, and the large number of possible inputs that can be
made for many tasks, there are a number of difficult problems in
defining such terms as task goals, subtasks, and dependent tasks. To
try to make clearer the definitions of these terms, NHTSA has prepared
and placed in the Driver Distraction Guidelines docket,\238\ a report
titled ``Explanatory Material About the Definition of a Task Used in
NHTSA's Driver Distraction Guidelines, and Task Examples.'' \239\
Persons interested in this issue are encouraged to read this report
which contains much information about task-related definitions beyond
what could be included in the NHTSA Guidelines (including numerous
detailed examples of tasks). Portions of this report have been relied
upon in this notice to clarify the definitions of goal, dependent task,
and subtask.
---------------------------------------------------------------------------

    \238\ Docket NHTSA-2010-0053. The docket is accessible at:
http://www.regulations.gov/.
    \239\ Angell, L., Perez, M., and Garrott, W.R., ``Explanatory
Material About the Definition of a Task Used in NHTSA's Driver
Distraction Guidelines, and Task Examples,'' accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0088,
posted May 18, 2012. Soon to be released as a NHTSA technical
report.
---------------------------------------------------------------------------

    In these NHTSA Guidelines, Goal is defined as a device state sought
by a driver. Goal achievement is defined as achieving a device state
that meets the driver's intended state, independent of the particular
device being executed or method of execution.
    The above mentioned NHTSA report expands on this with the
following:

    In the definition of ``goal'' used in the Phase 1 NHTSA
Distraction Guidelines, the state sought by a driver is defined in
terms of a ``device state.'' This means the goal is defined in terms
of a state that can be observed objectively on the HMI. The
individual who has the goal is the ``participant in the test.'' All
the participants in a test will be given the goal by a tester (and
goals for testable tasks will typically be meaningful ones, which
might be performed by real drivers on the devices). More will be
said about this later; suffice it to say now that planning prior to
testing will identify the ``goals'' and ``tasks'' given to
participants during testing. An example of a goal that is a ``device
state'' would be ``radio on'' (as in, ``Your goal is to turn the
radio on. Please begin now.''). This is a state of a device that can
be objectively verified, perhaps in several ways, depending on the
design. For example, a radio in the ``on'' state will produce
``sound'' (if its volume is set to an audible level), it may
generate visual messages on the associated display, and its
associated control may have an indicator which will identify the
state to which it is set.
    Goals (unlike sub-goals) typically are hardware-independent, and
may be achieved in virtually any vehicle. Their achievement can be
verified regardless of the particular method used to achieve the
goal. For example, ``turn the radio on'' is a goal that typically
could be achieved in any vehicle equipped with a radio. Also,
regardless of whether it is turned on with a push-button, a rotary
knob control, or with a voice command, achievement of the goal state
(of the radio being ``on'') can be verified objectively from the
state of the device itself.\240\
---------------------------------------------------------------------------

    \240\ Ibid, p. 20.

    In these NHTSA Guidelines, Dependent Task is defined as a task that
cannot be initiated until another task (the antecedent task) is
completed. The task's start state is thus dependent upon the end state
of another, antecedent, task.
    An antecedent task followed by a dependent task can be
distinguished from a task that contains two subtasks by examining the
end states of both the antecedent task and the dependent task. For the
antecedent task-dependent task case, both tasks will end with the
achievement of a driver goal (i.e., two driver goals will be achieved,
one for the antecedent task and one for the dependent task). In
contrast, for a task composed of two subtasks, only one driver goal
will be achieved.
    For example, after choosing a restaurant from a navigation system's
point-of-interest list (antecedent task), a driver is offered an
internet function option of making a reservation at the restaurant
(dependent task). The dependent task of making a reservation can only
be initiated following the task of selecting a restaurant from within
the navigation system.
    The above mentioned NHTSA report contains several examples of
dependent tasks (see Examples 2A, 2B, and 2M, as well as 4A.1-A.5.)
\241\
---------------------------------------------------------------------------

    \241\ Ibid, pp. 78-82, 112-113, and 153-164.
---------------------------------------------------------------------------

    In these NHTSA Guidelines, Subtask is defined as a sub-sequence of
control operations that is part of a larger testable task sequence--and
which leads to a sub-goal that represents an intermediate state in the
path to the larger goal toward which a driver is working.
    Subtasks should not be treated as separate dependent tasks. For
example, entering the street name as part of navigation destination
entry is not a separate task from entering the street number; rather,
these are subtasks of the same task.
    The above mentioned NHTSA report expands on this with the
following:

    * * * subtasks are sub-sequences of activity that represent
achievement of only an intermediate step along the path to goal
achievement, namely the sequence of activity required to reach a
sub-goal. Drivers typically will persist beyond a sub-goal and
continue with task activity through to the next sub-goal (and
beyond), until the task is completed. And, like sub-goals or tasks,
subtasks may be hardware or HMI dependent. They may vary in their
details and in their order within a task, depending on the device,
its functionality, and/or its HMI. * * * When entering a destination
in a navigation system, one system may require entry of the STATE
first and another may require its entry last. This is an indication
that the subtask sequence of entering the STATE portion of the
destination is a subtask within the entire task of entering a
destination. The nature and order of the subtasks (done to reach
sub-goals) depends upon the particular navigation system being
used.\242\
---------------------------------------------------------------------------

    \242\ Ibid, p. 29.

    In answer to Honda's request for clarification, the task of tuning
a radio in preparation for listening to it would be comprised of three
subtasks. As Honda states, these would be:
    1. Turning the radio on (subtask),
    2. Selecting AM or FM (subtask), and
    3. Selecting the frequency (subtask).
    Subtasks after the initial one during a task frequently depend upon
the prior subtasks that comprise a task. NHTSA has not designated these
non-initial subtasks as dependent subtasks since we do not think that
it helps people understand the task decomposition.
    As stated earlier, due to the large number of possible electronic
device-related secondary tasks, and the large

number of possible inputs that can be made for many tasks, it is
difficult to give clear, all-encompassing definitions of such terms as
task goals, subtasks, and dependent tasks. NHTSA has tried to make our
task-related definitions as clear as we can, but there may well be some
situations for which application of these definitions is difficult.
Organizations should feel free to bring these specific cases to NHTSA's
attention via the previously-mentioned interpretation letter process
and NHTSA will try to consistently apply its definitions to these
difficult cases.

H. Driving Simulator Issues

1. Driving Simulator Specifications
a. Summary of Comments
    Several organizations provided comments requesting clarification
about and/or making suggestions for specifications of simulators that
can be used for testing under the proposed guidelines. Commenters
included auto manufacturers (Volvo and BMW), research organizations
(VTI [Swedish Road and Transport Research Institute] and the University
of Iowa [National Advanced Driving Simulator and Simulation Center or
NADS]), and a simulator development company (Realtime Technologies
Inc.).
    The NADS provided the following general comments:

    There are many different kinds of driving simulators used by the
human factors research community today and we feel some additional
clarification in the guidelines as to what NHTSA intends to include
and exclude in its testing protocols is needed.\243\
---------------------------------------------------------------------------

    \243\ Comments received from the University of Iowa, National
Advanced Driving Simulator and Simulation Center, p. 1. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0071.

---------------------------------------------------------------------------
    Volvo provided the following general comment:

    Simulator dimensions are dependent on the simulator software,
the kind of simulator (fixed or moving base) and the kind of
projection screen used (flat or 180 [degrees, presumably in a wrap-
around configuration]). Volvo Cars has modern car simulator test
facilities that are suitable for the recommended test procedures;
however, it does not meet some specific recommendations when it
comes to locations and placements. Thus, we believe that the
simulator specifications should be more flexible.\244\
---------------------------------------------------------------------------

    \244\ Comments received from Volvo Cars, p. 4. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0104.

---------------------------------------------------------------------------
    BMW offered the following general comment:

    BMW has a state of the art driving simulator that is used for
purposes of testing any effect of current and new features on the
performance of the driver. BMW therefore considers the proposed
driving simulator specifications in the Federal Guidelines as
suggested minimum criteria.\245\
---------------------------------------------------------------------------

    \245\ Comments received from BMW Group, p. 6. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0094.

    In addition to these general comments, specific comments were
submitted pertaining to details of the simulator specifications
contained in the proposed guidelines. Comments regarding the projection
---------------------------------------------------------------------------
system were prevalent, including the following comments from VTI:

    Screen locations ranging from 2.5 m and more from the driver eye
point are quite sufficient.\246\
---------------------------------------------------------------------------

    \246\ Comments received from Swedish National Road Transport
Institute (VTI), p. 2. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 0056.

    The resolution of the computer generated image seems to be quite
under specified and should also benefit to be calculate using the
driver's eye point as references.\247\
---------------------------------------------------------------------------

    \247\ Ibid.
---------------------------------------------------------------------------

    The resolution should be given in dpi, to make the value
independent of the screen size.\248\
---------------------------------------------------------------------------

    \248\ Ibid.

    On this same topic, the following comments were provided by the
---------------------------------------------------------------------------
NADS group:

    As currently specified [the guidelines] would exclude those
systems which use computer display monitors rather than projectors.
* * * there is no research evidence of which we are aware to support
the use of projected imaged over monitor displays. Indeed, in order
for these guidelines to be useful in the future, it may be best to
avoid any reference to a single display method as the technology in
this industry is rapidly changing. In addition to a resolution
specification, the guidelines should also include some specification
for field-of-view of the display. * * * it is unclear if the intent
was to recommend only front-projection single-screen systems to the
exclusion of other display technologies.\249\
---------------------------------------------------------------------------

    \249\ Comments received from the University of Iowa, National
Advanced Driving Simulator and Simulation Center, p. 1. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0071.

    Realtime Technologies cited research results supporting the
---------------------------------------------------------------------------
following specific suggestions on this topic:

    * * * the minimum screen distance should be 3000 mm rather than
4700 mm.\250\
---------------------------------------------------------------------------

    \250\ Comments received from Realtime Technologies, Inc., p. 1.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0053.

    Drivers do not get additional accommodation depth cues for
distances beyond 2000 mm while convergence depth cues can be used to
10000 mm (Andersen, 2011). The literature states that for
comfortable viewing (both accommodation and convergence) the
distance should be at least 3000 mm (Lambooij, IJsselsteijn,
Heynderickx, 2007). Comfortable accommodation distances start at
2000 mm (Andersen, 2011).\251\
---------------------------------------------------------------------------

    \251\ Ibid.

    The resolution for the simulator should be specified in arc
minutes per pixel rather than a particular screen size and
resolution. This allows for a variety of screen configurations. The
FAA requires their aviation training simulators to have an effective
resolution of 3 arc-min/pixel or less (Stoner, Fisher, Mollenhauer,
2011). The simulator described in the guidelines meets this
requirement with a value of 1.7 arc-min/pixel. While visual acuity
can be as high as 0.5 arc-min/pixel, looming cues are the most
important aspect for car following and therefore driver distraction
(Andersen, 2011). Plotkin's research (1984) suggests, at a visual
update rate of 30 times per second (as specified in the guidelines),
the effective resolution where a human can detect any looming cue
will be 3.11 arc-min/pixel. Therefore we recommend that the minimum
resolution for these tasks be set at 3 arc-min/pixel.\252\
---------------------------------------------------------------------------

    \252\ Ibid.

---------------------------------------------------------------------------
    Questions about other simulator specifications were raised by NADS:

    It is not clear if NHTSA intends to exclude driving simulators
which use open cabs, partial cabs, and/or non-automotive seating and
dashboard arrangements.\253\
---------------------------------------------------------------------------

    \253\ Comments received from the University of Iowa, National
Advanced Driving Simulator and Simulation Center, p. 1. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0071.

    Section V12.b included some description of the vehicle controls.
This statement could be interpreted to exclude many simulators in
use by University and Industry researchers which utilize gaming
controls for steering and pedal driver inputs.\254\
---------------------------------------------------------------------------

    \254\ Ibid.
---------------------------------------------------------------------------

    Further information on whether or not force feedback must be
present on the steering wheel and pedals is also needed.\255\
---------------------------------------------------------------------------

    \255\ Ibid.

    It is not clear if NHTSA's intent was to exclude simulators with
motion.\256\ VTI raised a concern about the driving simulator's vehicle
dynamics simulation:
---------------------------------------------------------------------------

    \256\ Ibid.

    The guidelines lack a description of the vehicle's behavior on
the road, i.e. the vehicle dynamics.\257\
---------------------------------------------------------------------------

    \257\ Comments received from the Swedish National Road Transport
Institute (VTI), p. 2. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 0056.
---------------------------------------------------------------------------

b. NHTSA's Response
    NHTSA appreciates the helpful comments that we have received on
this issue. In response, we have modified our recommended driving
simulator specifications so that task acceptance testing may be
performed on a broader variety of driving simulators.

    Before explaining the individual changes that we have made in
response to comments to the recommended NHTSA driving simulator
specifications, it may help to first explain NHTSA's goals for driving
simulators.
    NHTSA believes task acceptance testing should be performable with
very simple, inexpensive, driving simulators. We recognize that not
every organization can afford to use the extremely high fidelity
National Advanced Driving Simulator or even higher fidelity, moving
base, driving simulators. We have deliberately tried to design our task
acceptance test so it can be run on a low-end driving simulator. This
does not preclude the use of a high-end simulator for task acceptance
testing, but merely acknowledges that a low-end simulator is adequate.
    While we want testing to be performable with low-end driving
simulators, NHTSA thinks that the driving simulators used for task
acceptance testing should generate a pattern of eye glances similar to
that seen when performing the same secondary task while driving an
actual motor vehicle. One of the key consequences of this belief is
that the roadway display should be far enough in front of the
simulator's driver that visual accommodation must occur when the driver
switches her gaze between the device interface and the roadway. In
other words, the driver's eyes should be focused approximately at
infinity when looking at the roadway and at the correct, much closer,
distance when looking at the device display.
    Focusing on specific comments, first of all, as BMW suggests, the
driving simulator specifications in the NHTSA Guidelines are suggested
minimum criteria. We certainly have no problems with better driving
simulators than specified in the NHTSA Guidelines but we do not want
ones with less fidelity. Similarly, NHTSA's Guideline recommendations
are not intended to exclude simulators with motion. Statements have
been added to the NHTSA Guidelines clarifying both of these points.
    In response to VTI's comment, the NHTSA Guidelines do not contain a
description of the vehicle dynamics because we believe the driving
scenario being simulated is extremely simple--straight line, constant
speed driving. Clearly the simulated vehicle needs to react
appropriately if the driver turns the steering wheel, presses the brake
pedal, or presses the throttle pedal. However, we do not think that an
elaborate vehicle dynamics model is necessary; something along the
lines of a linear three degree of freedom (lateral velocity,
longitudinal velocity, and yaw rate) vehicle model should be quite
sufficient. Again, if desired, more complex and accurate vehicle
dynamics may be used, but they are not necessary. Statements have been
added to the NHTSA Guidelines clarifying this point.
    In response to the NADS comments, NHTSA does not intend to exclude
driving simulators using open or partial cabs. While NHTSA intends to
perform its driving simulator based monitoring testing using actual
production vehicles and actual copies of the electronic devices being
tested, we do not think that every organization wanting to perform
Guideline conformance testing has to use such a driving simulator. The
important thing is that the driving simulator has a seating and
dashboard arrangement similar to an actual production vehicle so that
realistic eye glance behavior will occur. We do not think that non-
automotive seating and dashboard arrangements are adequate for task
acceptance testing.
    NHTSA does not think that gaming controls for driver steering will
provide an adequate level of realism. We believe an actual vehicle
steering wheel mounted in a typical vehicle arrangement is necessary.
Otherwise driver hand motions may not be realistic. For similar
reasons, we think that force feedback should be present on the driving
simulator's steering wheel. However, a linear feel (i.e., the restoring
force is directly proportional to the amount of steering) should be
adequate.
    Gaming style pedal controls are adequate since current task
acceptance tests do not use any metrics that will be affected by the
movement of the driver's feet. However, we do think that pedal force
feedback should be provided to assist the driver in maintaining a
constant speed. Again, very simple but realistic pedal force feedback
should be adequate.
    Statements clarifying all of these points have been added to the
NHTSA Guidelines.
    NHTSA did not intend to exclude driving simulators using computer
display monitors rather than projectors. Similarly, multiple screen
visual displays and rear-project display technologies are perfectly
acceptable.
    As suggested by the commenters, we have modified the NHTSA
Guidelines to permit any display technology to be used. NHTSA's goal is
to have the driving simulator display full-color, true-perspective,
three-dimensional scenes (as viewed by the driver) free from
distracting anomalies, such as abrupt changes in scene content,
aliasing problems in image processing, and abrupt changes in
illumination, color, or intensity (i.e., no flickering or flashing).
NHTSA's Guideline recommendations do not show preference toward one
display technology over others.
    NHTSA has decided to accept the suggestion offered by NADS and
Realtime Technologies that the NHTSA Guidelines should specify the
field-of-view of the display. We have set the minimum recommended
field-of-view to have a width of 30 degrees. Of course, wider fields-
of-view may be used.
    NHTSA has also decided to accept the suggestion offered by NADS and
Realtime Technologies that the NHTSA Guidelines should specify the
resolution for the simulator in arc minutes per pixel rather than a
particular screen size and resolution. The supporting research offered
by Realtime Technologies 258, 259, 260 is quite convincing.
Therefore, the recommended screen resolution is being set to 3 arc
minutes per pixel or better.
---------------------------------------------------------------------------

    \258\ Stoner, H. A., Fisher, D. L., Mollenhauer, M. A.,
``Simulator and Scenario Factors Influencing Simulator Sickness,''
in Fisher, D. L., Rizzo, M., Caird, J. K., and Lee, J. D. (Editors).
Handbook of Driving Simulation for Engineering, Medicine, and
Psychology, Boca Raton, FL, CRC Press, 2011.
    \259\ Andersen, G. J., ``Sensor and Perceptual Factors in the
Design of Driving Simulation Displays,'' in Fisher, D. L., Rizzo,
M., Caird, J. K., and Lee, J. D. (Editors)., Handbook of Driving
Simulation for Engineering, Medicine, and Psychology, Boca Raton,
FL, CRC Press, 2011.
    \260\ Plotkin, S., ``Multiple Causation,'' Automotive
Engineering and Litigation, 1, pp. 215-228, New York, Garland Law
Publishing, 1984.
---------------------------------------------------------------------------

    NHTSA received recommendations from NADS to reduce driver eye point
to screen distance minimum distance from the 4.7 meters originally
proposed in the NHTSA Guidelines to either 2.5 meters (NADS) or 3.0
meters (Realtime Technologies). The original 4.7 meter distance was
based on nothing more than the driver eye point to screen distance of
the NHTSA driving simulator located at NHTSA's Vehicle Research and
Test Center and the perception that this distance provides adequate
visual accommodation.
    To attempt to determine the minimum driver eye point to screen
distance in a more scientific manner, depth of field calculations were
used.
    As previously stated, the roadway display should be far enough in
front of the simulator's driver that visual accommodation must occur
when the driver switches his gaze between the device interface and the
roadway. NHTSA wants the driver's eyes to be focused approximately at
infinity when looking at the roadway and at the correct, much closer,
distance when looking at the device display. In terms

of depth of field, NHTSA translated this into having the ``far'' edge
of the depth of field at infinity.
    In order to perform a depth of field calculation, we needed values
for the image focal length of the human eye, the lowest f-stop to be
used in the calculation, and the permissible circle of confusion.
According to ``The Physics Factbook'' \261\ article on ``Focal Length
of a Human Eye'' a good value for the image focal length of the eye is
22.3 mm. The lowest achievable f-stop is equal to the image focal
length divided by the maximum eye pupil size. Human eye pupil size data
was obtained from a paper by Winn, Whitaker, Elliot, and Phillips.\262\
According to this, the maximum eye pupil size is approximately 9 mm
giving a minimum f-stop of 2.4 (rounded down to the nearest
``standard'' f-stop of f-2 for subsequent calculations).
---------------------------------------------------------------------------

    \261\ ``The Physics Factbook,'' edited by Glen Elert--written by
his students, accessed at: http://hypertextbook.com/facts/2002/JuliaKhutoretskaya.shtml on July 20, 2012.
    \262\ Winn, B., Whitaker, D., Elliot, D.B., and Phillips, N.J.,
``Factors Affecting Light-Adapted Pupil Size in Normal Human
Subjects,'' Journal of Investigative Ophthalmology and Visual
Science, March 1994, Vol. 35, No. 3, accessed at: http://www.iovs.org/content/35/3/1132.full.pdf on July 20, 2012.
---------------------------------------------------------------------------

    An acceptable value for circle of confusion was obtained from the
internet posting ``DOF--Demystifying the Confusion.'' \263\ According
to this posting, the normal human eye can determine 5 line pairs per
millimeter at a distance of 25 cm. Therefore, an acceptable circle of
confusion value is 0.2 mm.
---------------------------------------------------------------------------

    \263\ Accessed at: http://www.rags-int-inc.com/PhotoTechStuff/DoF/ on July 20, 2012.
---------------------------------------------------------------------------

    Inputting all of this data into a depth of field calculator \264\ a
hyperfocal distance (the distance beyond which all objects can be
brought into an acceptable focus) of 1.27 meters was calculated. The
minimum driver eye point to screen distance determined in this manner
would be 1.27 meters.
---------------------------------------------------------------------------

    \264\ The one used was called DOFMaster and accessed at: http://www.dofmaster.com/doftable.html on July 20, 2012.
---------------------------------------------------------------------------

    NHTSA has decided to round this 1.27 meter value up to 2.0 meters.
This takes NHTSA to the same value that, in their comments, Realtime
Technologies pointed out had been arrived at by other researchers.\265\
Based on the preceding analysis, we believe that having a minimum
driver eye point to screen distance will provide adequate visual
accommodation. This change has been incorporated into the NHTSA
Guidelines.
---------------------------------------------------------------------------

    \265\ Andersen, G. J., ``Sensor and Perceptual Factors in the
Design of Driving Simulation Displays,'' in Fisher, D. L., Rizzo,
M., Caird, J. K., and Lee, J. D. (Editors)., Handbook of Driving
Simulation for Engineering, Medicine, and Psychology, Boca Raton,
FL, CRC Press, 2011.
---------------------------------------------------------------------------

2. Suggestions To Improve the Driving Scenario
a. Summary of Comments
    Several comments were directed at the simulator scenario proposed
for use in the testing. Specifically, the Swedish Road and Transport
Research Institute (VTI) asked:

    In general, is the specified scenario difficult enough? \266\
---------------------------------------------------------------------------

    \266\ Comments received from the Swedish National Road Transport
Institute (VTI), p. 2. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 0056.
---------------------------------------------------------------------------

    Are the results generalizable to more complex traffic
environments? If not, the test will only show that it is `safe' to
perform the secondary task on straight road segments with one lead
vehicle. What happens when the device is used in urban traffic?
\267\
---------------------------------------------------------------------------

    \267\ Ibid.

    In contrast, several organizations advocated the use of the
Alliance driving task. As the basis for this recommendation, Mercedes-
---------------------------------------------------------------------------
Benz provided the following comment:

    The Alliance driving task was designed to mimic the relatively
benign conditions associated with distraction related crashes based
on real world data. NHTSA proposes altering this procedure * * * It
is unclear how the proposed changes to the driving procedure relate
to real world crash risk.\268\
---------------------------------------------------------------------------

    \268\ Comments received from Mercedes-Benz USA, LLC, p. 9.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0093.

    Several commenters suggested that data collection should include
curved in addition to straight road segments to ensure that steering
corrections are required.
    Numerous comments pertaining to scenario details were provided. VTI
pointed out that the guidelines lack specification of basic geometries,
including lane width, road markings, and road surface properties
(color, brightness, grain). They also noted that:

    * * * objects beside the road will influence the driver's
performance in navigating as these also provide sensation about
speed and heading as examples.\269\
---------------------------------------------------------------------------

    \269\ Comments received from the Swedish National Road Transport
Institute (VTI), p. 2. Accessed at www.regulations.gov, Docket
NHTSA-2010-0053, Document Number 0056.

    Several comments asked for more detailed information about the
proposed car-following task, including more detail about the speed of
the lead vehicle and its appearance, including size, shape, color, and
the way in which it appears in the driving scene.
    Additional detail was also requested about the proposed visual
detection task. The following comment was submitted by the University
of Iowa:

    Section VI.2.f.i specifies a ``filled-in, red circle'' but does
not specify the surrounding or background visual features. A red
circle will be nearly invisible against a dark sky. The guidelines
would be improved if this specification was expressed as a minimum
and maximum contrast ratio as used by the Federal Highway
Administration's Minimum Retroreflectivity Levels for traffic signs
(FHWA Docket No. FHWA-2003-15149).\270\
---------------------------------------------------------------------------

    \270\ Comments received from the University of Iowa, p. 2.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0071.

b. NHTSA's Response
    NHTSA has deliberately recommended a very simple driving scenario
for the Eye Glance Measurement Using a Driving Simulator acceptance
test protocol--straight line, constant speed driving. This does mimic
the Alliance Guidelines driving simulator scenario; the Mercedes-Benz
comment was made about NHTSA's proposed Dynamic Following and Detection
acceptance test options which, as previously discussed, are not being
carried forward at this time.
    The very simple driving simulator scenario proposed by NHTSA in the
Initial Notice was chosen for two reasons:
     Its simplicity should accommodate organizations that only
have low fidelity, low cost, driving simulators. Not everyone can
afford to use the extremely high fidelity National Advanced Driving
Simulator or even higher fidelity, moving base, driving simulators.
However, since the acceptance test protocol uses a straight line,
constant speed, drive and all of the criteria used to determine task
acceptance are based on driver eye glances, we do not believe it is
necessary to have a high fidelity driving simulator to perform this
testing. A low-fidelity driving simulator is sufficient.
     Since NHTSA has based its acceptance test criteria on test
participant performance while performing the reference task (manual
radio tuning) while driving this simple scenario, the effects of
scenario difficulty level are expected not to matter. If NHTSA were to
recommend a more complex scenario, with curving roads and more traffic,
it might degrade test participant performance while performing a
candidate task. However, it would also degrade test participant
performance while performing manual radio tuning, probably by about the
same amount. Therefore, tasks that meet the current acceptance test
criteria would probably also meet the

requirements of an acceptance test protocol that used a more complex
driving scenario. While NHTSA recognizes that its acceptance test
scenario is not typical of urban traffic environments, based on the
above logic, we believe the results to be generalizable to more complex
traffic environments.
    NHTSA also does not think that segments of the simulated road
driven during data collection should include curved road segments.\271\
While the inclusion of curved road segments would ensure that driver
steering corrections are required during testing, once again any
effects are expected to be present during both candidate task
acceptance testing and the testing used to determine the acceptance
criteria. Therefore, the effects are expected to cancel each other out.
Using straight roads during testing has one advantage: it reduces the
complexity of the needed driving simulator.
---------------------------------------------------------------------------

    \271\ NHTSA believes that it is a good idea to include curving
road segments during non-test portions of the drive that occur
between the straight segments of simulated road that are used during
testing.
---------------------------------------------------------------------------

    In response to the comments that were received, NHTSA has added
recommendations for road environment, road material and color, lane and
shoulder widths, and road markings to the Recommended Driving Simulator
Scenario subsection of the NHTSA Guidelines. The road markings portion
of these recommendations was taken from Section 3A.05, Widths and
Patterns of Longitudinal Pavement Markings contained in the
``California Manual on Uniform Traffic Control Devices for Streets and
Highways: Part 3--Markings.'' \272\ We have also added additional
recommendations about the lead vehicle appearance and that it suddenly
appears in the driving scene.
---------------------------------------------------------------------------

    \272\ ``California Manual on Uniform Traffic Control Devices for
Streets and Highways: Part 3 (FHWA's MUTCD 2003 Edition, as amended
for use in California)--Markings,'' pp. 3A-2--3A-3, State of
California, Business, Transportation and Housing Agency, Department
of Transportation, accessed at http://www.dot.ca.gov/hq/traffops/signtech/mutcdsupp/pdf/camutcd/CAMUTCD-Part3.pdf on July 10, 2012.
---------------------------------------------------------------------------

    Finally, the request for additional details about the proposed
visual detection task is only relevant to NHTSA's proposed Dynamic
Following and Detection acceptance test options which, as previously
discussed, are not being carried forward at this time.

I. Test Participant Issues

1. Test Participant Demographics
a. Summary of Comments
    Comments on this topic referred to the age groupings proposed by
NHTSA. The following comment from Global Automakers suggested that the
sample composition should better reflect the overall distribution of
drivers.

    Global Automakers does not believe that specific driver
populations should be over-weighted or underweighted during subject
selection, compared to the distribution of the driving population.
For example, while specific age groups may presently use technology
at different frequencies, those use patterns may change over time.
Therefore, we do not support increased representation of younger
drivers (18 through 24 age range) based on anecdotal indications
that this group currently uses electronic technology more
frequently.\273\
---------------------------------------------------------------------------

    \273\ Comments received from Global Automakers, p. 6. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0099.

    Mercedes-Benz expressed concern with the practical difficulties of
---------------------------------------------------------------------------
adhering to the proposed age/gender requirements:

    The proposed requirement for 24 participants, even mix of
genders and divided in 4 groups with each 6 human subjects in the
age range of 18-24, 25-39, 40-54 and 55-75 is extremely aggressive
and will make filling the subject pool difficult.\274\
---------------------------------------------------------------------------

    \274\ Comments received from Mercedes-Benz, p. 10. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0093.

    Mercedes-Benz also suggested that the sample be composed of
individuals that reflect the population of drivers most likely to use a
---------------------------------------------------------------------------
technology being tested:

    * * * it can be concluded that the applications or functions to
be tested should be evaluated by those age groups which are most
likely to buy the new features.\275\
---------------------------------------------------------------------------

    \275\ Ibid, p. 10.

---------------------------------------------------------------------------
    Hyundai provided the following comment:

    Hyundai requests NHTSA provide justification for the sample size
and demographic requirements. Hyundai proposes the agency change the
distribution of the participants based on current research.\276\
---------------------------------------------------------------------------

    \276\ Comments received from Hyundai Motor Group, p. 2. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0102.

    They cited two experimental studies to support the following
---------------------------------------------------------------------------
recommendation:

    Hyundai recommends the agency combine the 18-24, and 25-39 age
group and distribute the participant age groups into three groups of
8 participants: Young (18-40), Middle (41-64), and Mature (65 and
older). The proposed age groups will focus on the performance effect
among the age groups where differences have been seen in previous
research.\277\
---------------------------------------------------------------------------

    \277\ Ibid, p. 3.

    According to Dr. Paul Green, ``The guidelines do not pay adequate
attention to elderly drivers.'' \278\ Although Dr. Green agreed with
NHTSA's assertion that older drivers are less frequent users of
electronic technology than younger drivers, he adds:
---------------------------------------------------------------------------

    \278\ Comments received from Dr. Paul Green, p. 7. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0052.

    * * * they take far longer to complete tasks and have much
greater difficulty with them, in particular the distracting visual-
manual tasks that are the topic of this docket. Furthermore, over
time, use by older individuals of all sorts of electronic devices is
increasing. Therefore, it is recommended that an additional group be
added to the sample, drivers ages 65 to 75 and equal in size to the
other groups.\279\
---------------------------------------------------------------------------

    \279\ Ibid, p. 7.

---------------------------------------------------------------------------
    The following comment was received from GM:

    GM concentrates on a worst-case age group: 45 to 65 years old.
Subjects in this age bracket generally have greater mean glance
times and longer total eyes-off-road times than younger subjects.
Consequently, findings base on this age group are generally more
conservative.\280\
---------------------------------------------------------------------------

    \280\ Comments received from General Motors LLC, Attachment, p.
3. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0103.

b. NHTSA's Response
    As the above comments indicate, probably the most controversial
question about test participant demographics is whether to underweight
older drivers in the NHTSA Guidelines sampling plan.
    As set forth in the Initial Notice, the NHTSA Guidelines
recommended that out of each group of 24 test participants used for
testing, there should be:
     Six test participants 18 through 24 years old, inclusive,
and
     Six test participants 25 through 39 years old, inclusive,
and
     Six test participants 40 through 54 years old, inclusive,
and
     Six test participants 55 or more years old.
    As stated in the Initial Notice, based on 2009 statistics,\281\ the
percentage of licensed drivers aged 18 years or older contained in each
of these four groups are:
---------------------------------------------------------------------------

    \281\ http://www.fhwa.dot.gov/policyinformation/statistics/2009/dl20.cfm.
---------------------------------------------------------------------------

     11.4 percent are 18 through 24 years old, inclusive, and
     26.8 percent are 25 through 39 years old, inclusive, and
     29.7 percent are 40 through 54 years old, inclusive, and
     32.1 percent are 55 or more years old.
    To have an unweighted sample we would have to have 25 percent of

licensed drivers aged 18 years or older contained in each of these four
groups. Therefore, NHTSA's sampling method: over represents drivers 18
through 24 years old, inclusive; approximately correctly represents
drivers 25 through 39 years old, inclusive; approximately correctly
represents drivers 40 through 54 years old, inclusive; and under
represents drivers 55 or more years old.
    There are two reasons for this. First, drivers in the 18 through 24
age range have a higher rate of fatalities (per 100,000 drivers in that
age range \282\ or per 100 million vehicle miles traveled \283\) than
drivers that are 25 years of age or older. Second, at least
anecdotally, younger drivers are more frequent users of electronic
technology than are older drivers. Therefore, NHTSA believes that this
age range should be overrepresented in each test participant sample.
---------------------------------------------------------------------------

    \282\ National Highway Traffic Safety Administration, ``Traffic
Safety Facts 2008,'' NHTSA Technical Report DOT HS 811 170, 2010.
    \283\ United States Government Accountability Office, ``Older
Driver Safety, Knowledge Sharing Should Help States Prepare for
Increase in Older Driver Population,'' Report to the Special
Committee on Aging of the United States Senate, GAO-07-413, April
2007.
---------------------------------------------------------------------------

    The 55 years and older age range is underrepresented in test
samples relative to their numbers in the general driving population.
While NHTSA considers it important that advanced electronic device
tasks be tested using drivers in this age range, as mentioned above,
older drivers are less frequent users of electronic technology than
younger drivers. Therefore, NHTSA is proposing to underweight this age
range with six test participants rather than the eight called for by
their numbers in the general driving population.
    Clearly there were diverse opinions as to the best sampling method
to use. Global Automakers suggested using an unweighted sample.
Mercedes-Benz essentially agreed with NHTSA that the sample be composed
of individuals that reflect the population of drivers most likely to
use a technology being tested, resulting in an over representation of
younger test participants. General Motors, Dr. Green, and Hyundai all
advocated changing to a sampling plan that would over represent,
instead of under represent, older drivers.
    NHTSA has worked out what the age ranges would be for a test
participant sampling method that equally represented all age groups.
Such a sampling method would have:
     Six test participants 18 through 32 years old, inclusive,
and
     Six test participants 33 through 44 years old, inclusive,
and
     Six test participants 45 through 57 years old, inclusive,
and
     Six test participants 58 or more years old.
    Clearly there are many other possible test participant sampling
methods that are possible by subdividing the licensed driver population
in different ways and overweighting or underweighting selected groups.
    After careful consideration of the comments received, NHTSA
continues to think that the best test participant sampling method for
driver distraction testing (although not necessarily for other topics)
over represents younger (ages 18 through 24, inclusive) drivers. We
continue to believe that the higher crash rates seen for this age group
of drivers and their more frequent use of advanced electronic
technology justify this over representation. Therefore, we are keeping
our proposed test participant age groupings in the NHTSA Guidelines.
    In response to Mercedes-Benz's concerns that there will be
practical difficulties in adhering to the proposed age/gender
requirements, NHTSA's experience shows that the most difficult age
range in which to recruit test participants for driver distraction
studies is the older age range. However, NHTSA is already
underweighting this age range. A number of commenters suggested that we
increase the number of older test participants. While NHTSA has
rejected doing this, we do not think it appropriate to reduce the
number of older test participants to make recruiting easier.
2. Test Participant Impartiality
a. Summary of Comments
    Automakers generally advocated the use of company employees for
testing. The following comment was provided by Volvo:

    Recruiting completely na[iuml]ve and unbiased test participants,
even from the general public can be difficult to arrange in an area
near an automotive industry. Considering the vast number of tests
that will need to be done, it is not feasible to arrange tests with
people from other parts of the country/world.\284\
---------------------------------------------------------------------------

    \284\ Comments received from Volvo Car Corporation, p. 5.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0108.

---------------------------------------------------------------------------
    Global Automakers agreed with Volvo:

    There are categories of employees who are not involved in
technology development, such as those working in accounting and
other administrative areas. Such employees should be allowed to
participate in a pilot study when critical design features cannot be
shared outside the company. This approach would avoid the release of
proprietary information and allow for development of critical
systems without the concern that new technologies and features might
be exposed before product launch. The Guidelines should allow the
participants in such tests to be manufacturer employees who are not
involved in technology matters.\285\
---------------------------------------------------------------------------

    \285\ Comments received from Global Automakers, p. 6. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0099.

    Similar concerns were expressed by Hyundai, Mercedes-Benz, and
Nissan. However, VTI, based on their research experiences, suggested
the opposite: ``* * * do not use OEM employees.'' \286\
---------------------------------------------------------------------------

    \286\ Comments received from the Swedish Road and Transport
Research Institute (VTI), p. 3. Accessed at www.regulations.gov,
Docket NHTSA-2010-0053, Document Number 0056.
---------------------------------------------------------------------------

b. NHTSA's Response
    To preserve the appearance of test participant impartiality, NHTSA
has decided that it will not use automaker employees during its
research and/or monitoring testing to determine conformance with the
NHTSA Guidelines. While automobile manufacturers do have multiple
categories of employees, many of whom are not involved in vehicle
systems or component development, NHTSA believes that automaker
employees will tend to be generally more knowledgeable about vehicles
and their current features than the average member of the public. With
this additional knowledge of vehicles and their latest features, the
employees may perform better in testing due to this exposure to the
automotive industry.
    That said, NHTSA is not opposed to manufacturers using their own
employees during their own testing. The reasons given above by Global
Automakers and Volvo are certainly valid as are those given by other
commenters. We believe that manufacturers can obtain valid, impartial
results from testing their own employees as long as the employees are
unfamiliar with the product being tested. However, NHTSA's testing will
not involve automobile manufacturer employees as participants.
3. Other Test Participant Qualifications
a. Summary of Comments
    GM felt that the guidelines were generally too restrictive in the
specification of test participant qualifications. They submitted the
following comment:

    [The] inclusion of sampling particulars and other language in
the proposal suggests expectation or presumption that OEMs would
test systems using the specified

sample. GM believes this to be overly prescriptive.\287\
---------------------------------------------------------------------------

    \287\ Comments received from General Motors LLC, Attachment, p.
3. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0103.

    GM proposed that NHTSA be more flexible about the number of test
---------------------------------------------------------------------------
participants required:

    GM's practice for evaluating tasks related to in-vehicle
electronics requires that at least 85% of the test sample complete
the task with a mean glance time less than two seconds and a total
eyes-off road time under 20 seconds. * * * In cases when the test
sample is fewer than 24, a sufficient percentage of the test sample
must pass validation criteria so that Type I errors are no more
common than if a 24 person sample was used. * * * GM believes this
method allows flexibility and expediency, while maintaining the 85%
threshold limit established in the Alliance Guidelines. Therefore,
GM recommends the proposed guideline adopt the 85% threshold limit
in the Alliance Guidelines, and not adopt specific sample
requirements.\288\
---------------------------------------------------------------------------

    \288\ Ibid.

    A comment from Mercedes-Benz addressed the mileage requirement for
---------------------------------------------------------------------------
test participants:

    The required mileage of 7,000 miles per year is too high. This
requirement limits the potential group of people which are qualified
as test participants without adding a necessary benefit. We believe
a minimum mileage requirement of 3,000 miles per year is
sufficient.\289\
---------------------------------------------------------------------------

    \289\ Comments received from Mercedes-Benz, p. 9. Accessed at
www.regulations.gov, Docket NHTSA-2010-0053, Document Number 0093.

    Mercedes-Benz also questioned the need for prospective participants
---------------------------------------------------------------------------
to be comfortable communicating via text messages:

    Regarding subject's comfort level with technology, we find that
average subjects are appropriate for evaluating systems such as
navigation or phoning based on social media. The requirement for the
test participants to be comfortable communicating via text messages
is too specific. It's based on the specific tests that NHTSA has
performed focusing on text entry with nomadic devices. If NHTSA's
intention is to have tech-savvy test participants, then only
considering text messaging experience as a criterion is too
narrow.\290\
---------------------------------------------------------------------------

    \290\ Ibid.

---------------------------------------------------------------------------
    Researchers from VTI suggested that the guidelines testing should:

    Use participants from different social groups and with different
education. We [VTI] once ran a study with a group of engineers vs. a
random selection of citizens, and secondary task performance was
strikingly higher for the engineers.\291\
---------------------------------------------------------------------------

    \291\ Comments received from the Swedish Road and Transport
Research Institute (VTI), p. 3. Accessed at www.regulations.gov,
Docket NHTSA-2010-0053, Document Number 0056.

b. NHTSA's Response
    In response to GM's concerns that the guidelines were generally too
restrictive in the specification of test participant qualifications, as
discussed earlier in this notice, NHTSA plans to perform future
monitoring to see what design revisions occur and find out how vehicle
makes/models conform to these Phase 1 Driver Distraction Guidelines.
Such monitoring testing by NHTSA or its contractors will adhere to the
test procedures set forth in the NHTSA Guidelines. However, this only
sets forth how NHTSA will test for conformance to these Guidelines;
manufacturers are free to use any test procedures that they prefer.
    Regarding GM's concerns that the NHTSA Guidelines recommended
testing too many test participants, manufacturers are free to assess
conformance to NHTSA's voluntary Guidelines through any means they
determine is appropriate. If there is a certain test protocol that a
manufacturer believes is more effective in assessing conformance with
these Guidelines using fewer participants, they are certainly free to
use that protocol.
    NHTSA has decided to adopt Mercedes-Benz's suggestion about the
mileage requirement for test participants. Reducing the required
mileage of 7,000 miles per year to 3,000 miles per year will make it
easier to recruit test participants while still testing people who
drive regularly. Appropriate changes have been made to the NHTSA
Guidelines.
    After careful consideration, NHTSA has also decided to remove the
recommendation that test participants be comfortable communicating via
text messages from its Guidelines. This recommendation was originally
included in the Guidelines based on NHTSA's testing experience. We
occasionally had test participants who were very uncomfortable using
any advanced electronic technology. This recommendation was intended to
screen out such test participants. However, upon reconsideration, NHTSA
thinks that such drivers who are part of the driving population and
should not be screened out. The Guidelines recommendation that test
participants have experience using a cell phone while driving is
sufficient to screen out technology novices or non-users.
    Regarding VTI's recommendation to include test participants from
different social groups and with different educational backgrounds, for
the reasons explained below, NHTSA does not believe there is sufficient
empirical data to support the need to add socioeconomic class and
education criteria to the test participant selection criteria in the
NHTSA Guidelines. Furthermore, adding such criteria would likely
increase the difficulty of test participant recruitment and may require
increasing the minimum number of required test participants.
    There is no NHTSA-generated data showing different eye glance
behavior while performing secondary tasks across different social
groups or different education levels. While VTI's concerns are
plausible, and the organization indicated that it has supporting
experimental data (although none were submitted along with their
comments), NHTSA does not believe there is a sufficient basis to
warrant balancing of these factors in task acceptance testing performed
in association with the NHTSA Guidelines. A test participant's eye
glance behavior while performing secondary tasks depends, at least in
part, on the psychological and physical capabilities of the test
participant. While these are known to change with test participant age
(part of the reason why the NHTSA Guidelines recommend testing a broad
age range of test participants), little is known about whether these
psychological and physical capabilities vary with socioeconomic class
or education level. In addition, it is unclear whether the differing
secondary task performance between engineers and randomly selected
citizens mentioned by VTI was due to factors like socioeconomic status
or education level or whether it was due to the engineers' additional
experience and expertise with vehicle technologies.
    For all of NHTSA's human factors testing, the agency attempts to
recruit test participants from a broad range of socioeconomic classes
by recruiting test participants through multiple outlets, such as
printed newspapers and internet postings. Therefore, any research and/
or monitoring testing to determine conformance with the NHTSA
Guidelines can be expected to use test participants from different
social groups and with different education levels. The agency's goal in
the NHTSA Guidelines is to specify suitable, robust test protocols that
are not unnecessarily complicated or costly. This includes the
participant recruitment aspects of the test protocols. Because there is
insufficient data to support adding socioeconomic and education
criteria to the NHTSA Guidelines, the agency is refraining from doing
so at this time. However, nothing in the NHTSA Guidelines prevents a
manufacturer from including additional test participant selection
criteria as part of its own test protocols.

4. Test Participant Instructions, Training, and Practice
a. Summary of Comments
    VTI questioned the potential effect of the test instruction that
the driver' primary responsibility is to drive safely at all times:

    With such an instruction, drivers could refrain from executing
the secondary task at all, which would render the evaluation
impossible. Instead, we suggest that the instructions be that
participants should prioritize the secondary task. The performance
can then be put in relation to the performance on the secondary task
while standing still. Having the participants focus on the secondary
task is most likely to have higher external validity, as drivers
often feel a high motivation to complete the secondary task at hand.
Thus, testing under such circumstances also reflects a ``worst-
case'' scenario, which probably is not uncommon.\292\

    \292\ Ibid.
---------------------------------------------------------------------------

    VTI also provided the following comment about the car-following
task instruction:

    The driver is instructed to `keep a constant following distance'
to the lead vehicle. Here one should consider to instruct the driver
to `keep a constant time headway' to the lead vehicle, as this is
better associated with a `safe' distance. Keeping a constant time
headway will also work when the lead vehicle has a variable
speed.\293\

    \293\ Ibid.
---------------------------------------------------------------------------

b. NHTSA's Response
    After careful consideration, NHTSA believes that it is essential
that test participants be instructed that the drivers' primary
responsibly is to drive safely at all times and therefore is keeping
the test participant instructions as they were proposed in the Initial
Notice. Since there is no risk of physical injury associated with
driving in a simulator, NHTSA is concerned that some test participants
may treat it like a video game and drive unsafely and atypically. NHTSA
believes that specific driving instructions help prevent this problem
(as does having properly trained in-simulator experimenters who take
appropriate corrective action if such happens). In NHTSA's entire
driving simulator testing, we have never had a test participant refuse
to perform a secondary task on the grounds of it being too complicated
to perform while driving.
    NHTSA prefers the test instruction of ``keep a constant following
distance to the lead vehicle'' to the one of ``keep a constant time
headway to the lead vehicle'' because we believe that the first
instruction is easier for participants to understand. Since NHTSA's
driving simulator acceptance test protocol involves only driving at
constant speeds, the two instructions have the same practical effect.
NHTSA acknowledges that we will need to modify this instruction if we
shift to a test where the lead vehicle has a variable speed.

J. Device Response Time Recommendations

a. Summary of Comments
    Several commenters addressed the proposed 0.25-second device
response time. One commenter asserted that the proposed maximum of 0.25
seconds is too stringent. The following comment was provided by
Mercedes-Benz

    The proposed maximum response time to a device input of 250 ms
is too stringent. While a system response within 250 ms after driver
input is likely, there may be certain applications or system
functions which respond slightly after 250 ms. Providing an
indication that the device is responding (like showing an hour
glass) if a system response is expected to occur slightly after 250
ms (e.g. 300-400 ms) is more distractive for the driver because she/
he can't even recognize the indication until it disappears
again.\294\
---------------------------------------------------------------------------

    \294\ Comments received from Mercedes-Benz USA, LLC, p. 8.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0093.

---------------------------------------------------------------------------
    Mercedes-Benz suggested the following alternative:

    The requirement provided in Alliance Guidelines Principle 3.5
comprehends this possibility and should be used instead: ``The
maximum system response time for a system input should not exceed
250 msec. If system response time is expected to exceed 2 seconds, a
message should be displayed indicating that the system is
responding.'' \295\
---------------------------------------------------------------------------

    \295\ Ibid.

    Two commenters raised concerns about possible adverse effects. The
---------------------------------------------------------------------------
following comment was provided by Global Automakers:

    Devices that require a longer response time would necessitate
provision of response indicators, which could clutter the display
area.\296\
---------------------------------------------------------------------------

    \296\ Comments received from Global Automakers, Inc.,
Attachment, p. 6. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0099.

    Nissan North America, Inc. requested clarification of the
application of the 0.25 second response time and used the task of
programming radio presets as an example. They provided the following
---------------------------------------------------------------------------
comment:

    Nissan requests that NHTSA clarify how the 0.25-second response
time proposed in Section V.10 applies to driver input actions which
by design take longer than 0.25 seconds. For example, the common
industry practice for programming radio station presets is to hold
down the programmed button (in excess of 0.25 seconds) until a chime
signifies that the button has been successfully programmed.'' \297\
---------------------------------------------------------------------------

    \297\ Comments received from Nissan North America, Attachment,
p. 3. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 0096.
---------------------------------------------------------------------------

    The proposal appears to either recommend against this practice
or at least require that ``clearly perceptible indication'' be given
to the driver while the driver is pressing and holding the
programmed button. Providing additional ``clearly perceptible
indication ``during this action would appear to be redundant and
could lead to confusion.\298\
---------------------------------------------------------------------------

    \298\ Comments received from Nissan North America, Attachment,
p. 3. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 096.

---------------------------------------------------------------------------
    Nissan also provided the following recommendation:

    We request that NHTSA use the 2-second response time recommended
in the AAM guidelines to allow such functionality, or clarify how
the response time is measured and in what situations it
applies.''\299\
---------------------------------------------------------------------------

    \299\ Ibid.

    Another commenter requested examples of the types of indicators
that would be considered acceptable. Global Automakers provided the
---------------------------------------------------------------------------
following comment:

    This provision specifies a minimum 0.25-second response time for
devices, unless a clearly perceptible indication'' is provided that
the device is responding. We request that the agency provide
examples of what would qualify as ``clearly acceptable'' indications
of device response. We also request that the agency provide a higher
minimum response time than 0.25 second.\300\

    \300\ Comments received from Global Automakers, Inc.,
Attachment, p. 6. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0099.
---------------------------------------------------------------------------

b. NHTSA's Response
    With this recommendation, NHTSA intended to match the
recommendations of the Alliance Guidelines Principle 3.5 and ISO 15005:
2002.\301\ The Criterion/Criteria section of Alliance Guidelines
Principle 3.5 reads:
---------------------------------------------------------------------------

    \301\ International Standard 15005:2002, ``Road Vehicles--
Ergonomic Aspects of Transport Information and Control Systems--
Dialogue Management Principles and Compliance Procedures.''

    Criterion/Criteria:
    The maximum system response time for a system input should not
exceed 250 msec. If system response time is expected to exceed 2
seconds, a message should be displayed indicating that the system is
responding.\302\
---------------------------------------------------------------------------

    \302\ Driver Focus-Telematics Working Group, ``Statement of
Principles, Criteria and Verification Procedures on Driver-
Interactions with Advanced In-Vehicle Information and Communication
Systems,'' p. 74, June 26, 2006 version, Alliance of Automobile
Manufacturers, Washington, DC.

    Following the receipt of these comments, NHTSA again carefully

reviewed this principle and researched the Alliance's rationale for
this criterion. NHTSA learned that the first sentence of the above
paragraph means that, as a ``best practice,'' an electronic device
should respond to a driver's input within 0.25 seconds. The second
sentence means that if the electronic device cannot conform to this
``best practice'' then after 2.0 seconds the device should provide an
indication to the driver that the device is in the process of
responding. We have changed the language of the NHTSA Guidelines to
reflect our improved understanding of this principle.
    In response to Nissan's comment about the common industry practice
of programming radio station presets by holding down the programmed
button until an auditory chime signifies that the button has been
successfully programmed, we have added language to the NHTSA Guidelines
indicating that the measurement of device response time should not
begin until the driver has completed her input (i.e., for radio preset
programming, response time measurement should only begin when the
driver releases the button).
    In response to Global Automakers' request that NHTSA provide
examples of what would qualify as ``clearly acceptable'' indications of
device response, we have decided to add a slightly modified version of
the following paragraph from the Alliance Guidelines to the NHTSA
Guidelines (in which the word ``system'' has been changed to
``device''):

    The system's response is clearly perceptible if it is obvious
for the driver that a change has occurred in the system and that
this change is the consequence of the input. If the change within
the system resulting from a given input is not systematically the
same but depends on one or more previous steps of the sequence, it
would be advisable to provide help (on driver request).\303\
---------------------------------------------------------------------------

    \303\ Ibid, p. 73.

    Since there may be multiple ways to meet the above recommendation
depending upon the precise details of the device interface, NHTSA is
unable to provide more precise guidance than that stated above.

K. Downward Viewing Angle Issues

a. Summary of Comments
    Numerous comments were received in reference to a discrepancy
between the versions of SAE J941, ``Motor Vehicle Drivers' Eye
Locations,'' used to determine the driver eye point when calculating
the downward display viewing angle. The Alliance Guidelines used the
1997 version of SAE J941 while the Initial Notice proposed that the
NHTSA Guidelines use the 2010 version. The Alliance explained the
discrepancy and its possible implications in the following comment:

    In the preamble to the [NHTSA Guidelines] proposal, the agency
acknowledges that its reference to the latest revision of SAE J941
is different than that referenced in the Alliance guidelines (2010
vs. 1997). Although the Alliance agrees that the differences between
the two versions are small, it is possible that some displays that
are on the boundary of the permissible zone might not comply with
the down angle requirements when measured using the revised (2010)
version of the standard. FMVSS requirements (and ISO requirements
that reference FMVSS) currently reference the old eyellipse. As a
result, OEMs would have to conduct CAD analyses multiple ways at
significant cost and no real safety benefit.\304\
---------------------------------------------------------------------------

    \304\ Comments received from the Alliance, Technical Appendix,
p. 23. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 0104.

    In their comments, Global Automakers made reference to a much
---------------------------------------------------------------------------
earlier version of SAE J941 in their summary of the problem:

    The proposed Guidelines use the March 2010 version of SAE
Recommended Practice J941 in determining the driver's eye point, for
purposes of determining the downward viewing angle to device
displays. The agency states that this eye point height is similar to
that used in the Alliance guidelines, which relies on the June 1997
version of J941 with 8.4 mm added to that height. For purposes of
compliance with safety standards (see, e.g., FMVSS 104 and by
reference FMVSS 111), a much earlier version of J941 is specified
(November 1965) and remains in use.\305\
---------------------------------------------------------------------------

    \305\ Comments received from Global Automakers, Attachment, p.
4. Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0099.

---------------------------------------------------------------------------
    The Global Automakers' recommended solution is:

    Since manufacturers' compliance systems are established on the
basis of these earlier versions we request that the Guidelines allow
determination of the downward viewing angle using any of these
versions of J941.\306\
---------------------------------------------------------------------------

    \306\ Ibid.

    The Alliance offered the following recommendation for how to deal
---------------------------------------------------------------------------
with the implications of adopting a new eyellipse:

    If the Agency wants to migrate to the new eyellipse, then all
FMVSS referencing the eyellipse and these guidelines should be
revised to allow the use of the new eyellipse, but should not yet
require it. Manufacturers would then be able to declare which
eyellipse they have used for each vehicle line during some interim
period of time, similar to the way the use of the Hybrid III dummy
replaced the Hybrid II over a number of years. This will allow
manufacturers to switch to the new eyellipse in an orderly fashion
as each vehicle line is redesigned. It will also allow each vehicle
design to utilize only one version of the eyellipse, and not require
that one be used for certain requirements and the other for
different requirements. Since most vehicle lines are redesigned
within a five to seven-year cycle, at least seven years should be
allowed once the new eyellipse is permitted, before it becomes
mandatory.\307\
---------------------------------------------------------------------------

    \307\ Comments received from the Alliance, Technical Appendix,
p. 23. Accessed at www.regulations.gov, Docket NHTSA-2010-0053,
Document Number 0104.

    Toyota Motor North America, Inc. provided specific detail about
another issue it (and other commenters) noticed in regards to the
---------------------------------------------------------------------------
maximum display downward viewing angle equations and proposed a remedy:

    The NHTSA Driver Distraction Guidelines correctly utilize the
Alliance equations for maximum display downward viewing angle on
page 11237, but use slightly different equations on page 11220.
Toyota requests NHTSA to correct the equations on page 11220 to
match those on page 11237 and the Alliance DF-T Guidelines.\308\
---------------------------------------------------------------------------

    \308\ Comments received from Toyota Motor North America, Inc.,
Attachment, p. 13. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0092.
---------------------------------------------------------------------------

    Toyota is making this request under the assumption that the
equations on page 11220 were a misprint, and not intended to adjust
the equations to account for the new reference eye point.\309\
---------------------------------------------------------------------------

    \309\ Ibid.

---------------------------------------------------------------------------
    Additionally, Toyota and Ford Motor Company requested:

    NHTSA to include notations regarding measurement of eye height
to ground in grid coordinates for 2D, and SAE curb ground line
coordinates in 3D, per the Alliance DF-T guidelines.\310\
---------------------------------------------------------------------------

    \310\ Ibid.

---------------------------------------------------------------------------
    Toyota further suggested that:

    * * * considering future display technology that may include
large multi-task displays or non-planar display surfaces, Toyota
proposes removing the definition for ``Active Display Area'' and
merging it into a new definition for ``Display Geometric Center.''
Display Geometric Center is a point on the active display area that
is the intersection of all lines that divide the display into two
parts of equal moment. Informally, one could imagine this as the
point where the active display area could balance on the point of a
needle. The active display area includes only the regions of the
display containing in-scope information subject to these guidelines,
and excludes portions of the display containing out-of-scope
information, unused display surface, and hard switches. For
reconfigurable displays, all possible display configurations must
meet the downward viewing angle criterion. Non-planar displays shall
define geometric center as the point on the display

surface nearest the actual display geometric center.\311\
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    \311\ Ibid, p. 14.

    On the related topic of obstruction of view, Ford and Toyota
recommended that NHTSA add Alliance Guideline's Principle 1.1 to the
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NHTSA Guidelines:

    The Alliance DF-T Principle 1.1 states that the system should be
located and fitted in accordance with relevant regulations,
standards, and the vehicle and component manufacturers' instructions
for installing the systems in vehicles. The guidelines provide a
verification method to confirm that the location and fit conform to
applicable standards, e.g., SAE, ISO and regulations, e.g., FMVSS,
CMVSS, and manufacturer-specific installation instructions.\312\
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    \312\ Comments received from Ford Motor Company, Appendix p. 9.
Accessed at www.regulations.gov, Docket NHTSA-2010-0053, Document
Number 0097.
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    We recommend that the NHTSA guidelines adopt the language
specified in the Alliance DF-T Guidelines and provide a verification
method as a confirmation test.\313\
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    \313\ Ibid.
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b. NHTSA's Response
    After careful consideration of all of the various comments received
on the issue of which version of SAE J941 should be used by the NHTSA
Guidelines, NHTSA has decided to partially adopt Global Automakers'
suggestion and allow the use of any one of several versions of SAE J941
which can be used to calculate the driver eye point.
    The effects of the version of SAE J941 used on the driver's
downward viewing angle when viewing displays are expected to be
minimal. Therefore, it is impossible to justify on a safety basis the
use of one version of SAE J941 instead of another. Without a safety
basis for choosing one version of SAE J941 instead of another, NHTSA
examined the research basis for the maximum display downward angle
recommendations.
    The research that forms the basis for the NHTSA Guidelines maximum
display downward angle recommendations is the research that underlies
the JAMA Guidelines \314\ recommendations on downward viewing angle. As
explained in the Alliance Guidelines:
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    \314\ Japanese Automobile Manufacturers Association, ``Guideline
for In-Vehicle Display Systems, Version 3.0, Annex 1: Display
Monitor Location,'' p. 5, Japanese Automobile Manufacturers
Association, Tokyo, Japan, August 2004.

    * * * these criteria are based on a reference point called the
Japanese eye point. In order to apply these practices in North
America in a way that is consistent with Japanese criteria, it is
necessary to establish a corresponding point in terms of North
American practice. In this principle, therefore, the term `eye
point' is the SAE equivalent of the JIS (Japanese Industrial
Standard) eye point,\315\ which is the SAE J941\316\ 2D eyellipse
side view intersection of XX and ZZ locator (datum) lines. This
corresponding point is located 8.4 mm up and 22.9 mm rearward of the
mid-eye centroid of the SAE eyellipse. \317\
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    \315\ JIS Eye Point is defined by JIS D0021 and JIS D1702.
    \316\ SAE J941 June 1997 revision.
    \317\ Driver Focus-Telematics Working Group, ``Statement of
Principles, Criteria and Verification Procedures on Driver-
Interactions with Advanced In-Vehicle Information and Communication
Systems,'' p. 16, June 26, 2006 version, Alliance of Automobile
Manufacturers, Washington, DC.

    As indicated in the preceding paragraph, certain offsets are used
to determine the JIS eyepoint from the mid-eye centroid of the SAE
eyellipse. The Alliance Guidelines provide the offsets when the 1997
version of SAE J941 is used (8.4 mm up and 22.9 mm rearward), but, for
the purposes of the NHTSA Guidelines, any version of SAE J941 for which
NHTSA knows how to obtain the JIS eye point could be used. Accordingly,
NHTSA has examined various versions of SAE J941 and is specifying in
the NHTSA Guidelines those versions from which the JIS eye point can be
calculated.
    The June 1992, September 2002, and October 2008 versions of SAE
J941 use the same equations as the June 1997 version to calculate the
mid-eye centroid of the SAE eyellipse, and accordingly, the same offset
is used to obtain the JIS eye point (8.4 mm up and 22.9 mm rearward).
Therefore, all three of these versions of SAE J941 are acceptable for
use with the NHTSA Guidelines.
    The March 2010 version of SAE J941 is also acceptable for use with
the NHTSA Guidelines but with a different offset to obtain the JIS eye
point. When using the March 2010 version of SAE J941, the JIS eye point
is at the mid-eye centroid of the SAE eyellipse.
    NHTSA examined several earlier versions of SAE J941, including the
November 1965 version referenced in FMVSS No. 104 and in Global
Automakers' comments, but was unable to determine the JIS eye point
from the mid-eye centroid of the eyellipse specified in those
standards. Accordingly, the agency is not specifying any earlier
versions of SAE J941 in the NHTSA Guidelines.
    In summary, NHTSA has modified its Guidelines so that any version
of SAE J941 from June 1992 or later is acceptable for use. The NHTSA
Guidelines specify the offsets used to calculate the JIS eye point for
each specific version of SAE J941.
    Turning to other issues raised in the above quoted comments, NHTSA
acknowledges that the equations in the preamble of the Initial Notice
(on Page 11220) were incorrect. The equations in the actual proposed
Guidelines, on Page 11237 of the Initial Notice, which are identical to
the ones in the Alliance Guidelines, are the correct equations. The
version of the Guidelines issued with this notice contains the correct
equations.
    When commenters requested that NHTSA include notations regarding
measurement of eye height to ground in grid coordinates for 2D, and SAE
curb ground line coordinates in 3D, we think that they are requesting
the addition of figures similar to Figures 1, 2, 5, and 6 in the
Alliance Guidelines. These figures are intended to clarify coordinates
and measurements used when calculating a display's downward viewing
angle. NHTSA intends to add similar figures to its Guidelines in the
future.
    NHTSA is deferring action on Toyota's suggestion that we remove the
definition for ``Active Display Area'' and merge it into a new
definition for ``Display Geometric Center.'' While it may be a viable
idea, NHTSA would like to further consider this issue and the potential
implications before acting upon it.
    Finally, the recommendation by Ford and Toyota that NHTSA add
Alliance Guideline's Principle 1.1 to the NHTSA Guidelines will be
considered in future Guidelines revisions.
    The subsection titled ``No Obstruction of View'' in the version of
the NHTSA Guidelines published with the Initial Notice contained
slightly reworded versions of Alliance Guideline's Principles 1.2 and
1.3. We did not include Alliance Guideline's Principle 1.1 in this
subsection because it seemed unnecessary.
    Alliance Guideline's Principle 1.1 reads:

    The system should be located and fitted in accordance with
relevant regulations, standards, and the vehicle and component
manufacturers' instructions for installing the systems in vehicles.

    While NHTSA certainly agrees with the contents of this principle,
NHTSA expects and assumes that everything in the design and manufacture
of a vehicle is done in accordance with relevant regulations and
standards. We also assume that OE electronic devices are installed in
vehicles as per the component manufacturers' instructions. Therefore,
we do not believe this principle adds anything to Phase 1 of NHTSA's
Guidelines. However, NHTSA

will keep this principle in mind when it develops its Guidelines for
portable and aftermarket devices (Phase 2 of NHTSA's Driver Distraction
Guidelines).

L. Miscellaneous Issues

1. Concerns About Recommendation That Drivers Should Have One Free Hand
a. Summary of Comments
    Several organizations made comments on the proposal that when
device controls are located on the steering wheel that no task should
require simultaneous manual input from both hands. The following
comment was provided by Global Automakers:

    The proposed Guidelines state that when device controls are
located on the steering wheel and both hands are on the steering
wheel, no device tasks should require simultaneous manual inputs
from both hands. We are concerned that this limitation may block
technical progress in developing new functions that have the
potential to enhance safety. For example, this requirement would
prohibit the use of paddle shifters which in some instances require
simultaneous input from both hands to operate. We recommend that the
agency include in this provision the exception in Principle 3.1,
page 67, Criterion/Criteria 3.1(b) of the Alliance Guidelines for
simultaneous manual inputs.\318\
---------------------------------------------------------------------------

    \318\ Comments received from Global Automakers, Inc.,
Attachment, p. 6. Accessed at www.regulations.gov, Docket NHTSA-
2010-0053, Document Number 0099.

---------------------------------------------------------------------------
    A similar comment was provided by the Hyundai Motor Group:

    Hyundai is concerned that simultaneous manual inputs from both
hands are not permitted for device controls located on the steering
wheel. Hyundai is concerned this recommendation will not allow the
use of paddle switches, and could limit future safety innovation.
Hyundai recommends that agency reconsider simultaneous manual inputs
as a method for device control.\319\
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    \319\ Comments received from Hyundai Motor Group, p. 3. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0102.

    In contrast to these concerns about the potential limiting effect
of this provision, Consumers Union provided the following comment in
---------------------------------------------------------------------------
support:

    We also support NHTSA's recommendation that all device functions
accessed via visual-manual interaction by the driver should be
operable by using, at most, one of the driver's hands. In
particular, we agree with NHTSA's modification of the Alliance of
Automobile Manufacturers guidelines, which would have allowed
simultaneous input from both hands for steering wheel device
controls, as long as one of the two hands maintains only a single
finger input. Controls that require simultaneous use of both hands
can create unsafe driving situations and should not be
utilized.\320\
---------------------------------------------------------------------------

    \320\ Comments received from the Consumers Union, p. 3. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0063.
---------------------------------------------------------------------------

b. NHTSA's Response
    After careful consideration of the comments received, NHTSA
continues to be concerned that tasks requiring the simultaneous use of
both hands, even one for which only a single finger input is required
from one hand (as per Principle 3.1, page 67, Criterion/Criteria 3.1(b)
of the Alliance Guidelines \321\), will result in an unsafe situation.
We continue to think that it overloads the driver's hands and makes
them less available (albeit not for very long) in the event that a
sudden emergency occurs. Therefore, the NHTSA Guidelines will continue
to recommend against driver interfaces that utilize this special case
of two-handed control.
---------------------------------------------------------------------------

    \321\ Driver Focus-Telematics Working Group, ``Statement of
Principles, Criteria and Verification Procedures on Driver-
Interactions with Advanced In-Vehicle Information and Communication
Systems,'' p. 67, June 26, 2006 version, Alliance of Automobile
Manufacturers, Washington, DC.
---------------------------------------------------------------------------

    Having said the above, we can alleviate Global Automakers and
Hyundai's concerns about the use of two hands to operate paddle
shifters or paddle switches. Vehicle controls, including paddle
shifters or paddle switches, are not within the scope of the NHTSA
Guidelines. We have added language to the NHTSA Guidelines to make this
point more clearly.
2. Concerns About Device Sound Level Control Recommendations
a. Summary of Comments
    Both Ford Motor Company and Toyota Motor North America, Inc.
submitted essentially identical comments about the device sound level
recommendation contained in the Initial Notice version of the NHTSA
Guidelines. Ford's comment is:

    The Alliance DF-T [the Alliance Guidelines] principle 2.4 states
that the system should not produce uncontrollable sound levels
liable to mask warnings from within the vehicle or outside or to
cause distraction or irritation. Our understanding is that it was
the Agency's intent to use the DF-T principle as written for the
NHTSA guidelines; however, the NHTSA guidelines do not offer a
verification method crucial to determine consistent application of
these guidelines. Also the term ``irritation'' is too subjective for
guidelines or verification.\322\
---------------------------------------------------------------------------

    \322\ Comments received from Ford Motor Company, p. 9. Accessed
at www.regulations.gov, Docket NHTSA-2010-0053, Document Number
0097.
---------------------------------------------------------------------------

    Ford recommends that the NHTSA guidelines adopt the language
specified in the Alliance DF-T Guidelines, and provide a
verification method as a confirmation test. The Alliance DF-T
Guidelines verification method for this principle states that system
sound level shall demonstrate adjustability down to a fully muted
level or demonstrate that there is no significant masking of audible
warnings concerning road and vehicle safety.\323\
---------------------------------------------------------------------------

    \323\ Ibid.
---------------------------------------------------------------------------

b. NHTSA's Response
    After careful consideration, NHTSA has decided that it agrees with
these comments. The word ``irritation'' is too subjective for use in
the NHTSA Guidelines. NHTSA believes that highly irritating sounds are
inherently distracting. Therefore, the modified version of this
recommendation would screen out highly irritating device sounds.
    NHTSA has included in the NHTSA Guidelines information about how to
verify that a device conforms to this recommendation. Therefore, we
have added (with minor wording changes to improve clarity) portions of
the paragraph under Criterion/Criteria in Principle 2.4 of the Alliance
Guidelines \324\ into the NHTSA Guidelines.
---------------------------------------------------------------------------

    \324\ Driver Focus-Telematics Working Group, ``Statement of
Principles, Criteria and Verification Procedures on Driver-