[Federal Register Volume 81, Number 47 (Thursday, March 10, 2016)]
[Proposed Rules]
[Pages 12647-12676]
[FR Doc No: 2016-05187]

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DEPARTMENT OF TRANSPORTATION

National Highway Traffic Safety Administration

49 CFR Part 571

[Docket No. NHTSA-2016-0029]
RIN 2127-AL68

Federal Motor Vehicle Safety Standards; Electric-Powered
Vehicles: Electrolyte Spillage and Electrical Shock Protection

AGENCY: National Highway Traffic Safety Administration (NHTSA),
Department of Transportation (DOT).

ACTION: Notice of proposed rulemaking (NPRM).

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SUMMARY: NHTSA is proposing to amend Federal Motor Vehicle Safety
Standard (FMVSS) No. 305, ``Electric-powered vehicles: Electrolyte
spillage and electrical shock protection,'' to adopt various electrical
safety requirements in Global Technical Regulation (GTR) No. 13,
``Hydrogen and fuel cell vehicles.'' To expand the standard's
performance requirements beyond post-crash conditions, NHTSA proposes
to adopt electrical safety requirements to protect against direct and
indirect contact of high voltage

sources during everyday operation of electric-powered vehicles. Also,
NHTSA proposes to adopt an optional method of meeting post-crash
electrical safety requirements consistent with that set forth in GTR
No. 13 involving use of physical barriers to prevent direct or indirect
contact (by occupants or emergency services personnel) with high
voltage sources. Today's proposal would facilitate the introduction of
new technologies including hydrogen fuel cell vehicles and 48 volt mild
hybrid technologies, and responds not only to GTR No. 13 but also to
petitions for rulemaking from Toyota Motor North America Inc. (Toyota)
and the Auto Alliance (Alliance).

DATES: Comments must be received on or before May 9, 2016.
    Proposed compliance date: We believe there is widespread
conformance of vehicles to the proposed requirements. Accordingly, we
propose that the compliance date for the amendments in this rulemaking
action would be 180 days after the date of publication of the final
rule in the Federal Register. We propose to permit optional early
compliance with the amended requirements.

ADDRESSES: You may submit comments to the docket number identified in
the heading of this document by any of the following methods:
     Federal eRulemaking Portal: Go to http://www.regulations.gov. Follow the online instructions for submitting
comments.
     Mail: Docket Management Facility, M-30, U.S. Department of
Transportation, West Building, Ground Floor, Rm. W12-140, 1200 New
Jersey Avenue SE., Washington, DC 20590.
     Hand Delivery or Courier: West Building Ground Floor, Room
W12-140, 1200 New Jersey Avenue SE., between 9 a.m. and 5 p.m. Eastern
Time, Monday through Friday, except Federal holidays.
     Fax:<PHONE_NUMBER>.
    Regardless of how you submit your comments, please mention the
docket number of this document.
    You may also call the Docket at<PHONE_NUMBER>.
    Instructions: For detailed instructions on submitting comments and
additional information on the rulemaking process, see the Public
Participation heading of the Supplementary Information section of this
document. Note that all comments received will be posted without change
to http://www.regulations.gov, including any personal information
provided.
    Privacy Act: Please see the Privacy Act heading under Rulemaking
Analyses and Notices.

FOR FURTHER INFORMATION CONTACT: For technical issues, you may call
William J. Sanchez, Office of Crashworthiness Standards (telephone:
202-493-0248) (fax:<PHONE_NUMBER>). For legal issues, you may call
Deirdre Fujita, Office of Chief Counsel (telephone:<PHONE_NUMBER>) (fax:
202-366-3820). Address: National Highway Traffic Safety Administration,
U.S. Department of Transportation, 1200 New Jersey Avenue SE., West
Building, Washington, DC 20590.

SUPPLEMENTARY INFORMATION:

Table of Contents

I. Executive Summary
II. FMVSS No. 305
III. The Global Technical Regulation
    a. Overview of the Process
    b. Overview of GTR No. 13
    1. Electric Safety Requirements During Normal Vehicle Operation
    2. Electric Safety Requirements Post-Crash Test
    c. How does this proposal differ from GTR No. 13?
IV. Battelle Study and Developments
V. Toyota Petition for Rulemaking
VI. Alliance Petition for Rulemaking
VII. Overview of Proposed Rule
VIII. Proposal Addressing Safety During Normal Vehicle Operations
IX. Proposal Addressing Safety Post-Crash
X. Rulemaking Analyses and Notices
XI. Public Participation

I. Executive Summary

    NHTSA is issuing this NPRM as part of the agency's ongoing effort
to harmonize vehicle safety standards under the Economic Commission for
Europe 1998 Global Agreement (``1998 Agreement''). The efforts of the
U.S. and other contracting parties to the 1998 Agreement culminated in
the establishment of GTR No. 13, ``Hydrogen and fuel cell vehicles.''
NHTSA voted in June 2013 in favor of establishing GTR No. 13. In this
NPRM, we are proposing requirements based on the electrical safety
requirements of GTR No. 13. NHTSA will initiate rulemaking in the
future on other aspects of GTR No. 13 directly pertaining to the fuel
system integrity of hydrogen fuel cell vehicles.
    One purpose of FMVSS No. 305 is to reduce deaths and injuries from
electrical shock. The standard requires vehicles with high voltage
sources to meet certain performance criteria to protect vehicle
occupants, rescue workers and others who may come in contact with the
vehicle after a crash. Among other things, FMVSS No. 305 requires that
after a crash, high voltage sources in a vehicle are either (a)
electrically isolated from the vehicle's chassis or (b) their voltage
is below specified levels considered safe from electric shock hazards.
Since the physiological impacts of direct current (DC) are less than
those of alternating current (AC), the standard specifies lower minimum
electrical isolation requirements for certain DC components (100 ohms/
volt) than for AC components (500 ohms/volt).
    GTR No. 13 also has requirements intended to reduce deaths and
injuries from electrical shock. Unlike FMVSS No. 305, GTR No. 13 has
requirements that reduce the risk of harmful electric shock during
normal vehicle operation. This NPRM proposes to adopt those
requirements to expand FMVSS No. 305's performance requirements beyond
post-crash conditions. In addition, while the various post-crash
compliance options in GTR No. 13 are similar to those in FMVSS No. 305,
GTR No. 13 includes a compliance option for electrical vehicle safety
that prevents direct and indirect contact of high voltage sources by
way of ``physical barriers.'' NHTSA is now proposing to amend FMVSS No.
305 to permit a physical barrier compliance option.\1\
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    \1\ Our proposed physical barrier option varies slightly from
GTR No. 13. GTR No. 13 provides contracting parties discretion in
whether to propose the option in their domestic regulatory process.
In our proposal today, we are not proposing to adopt GTR No. 13's
physical barrier option. However, as further discussed, below, we
are adopting a modified physical barrier option that we believe will
also afford the compliance flexibility that GTR No. 13 seeks to
provide, while at the same time providing a level of safety closer
to the other post-crash compliance options. A small number of minor
additional provisions are proposed as well. These additional
provisions would not significantly alter our incorporation of GTR
No. 13 and are consistent with the goal of incorporating a standard
that is harmonized with other international standards.
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    NHTSA tentatively believes that the by-product of adopting a
physical barrier option would be more than harmonizing vehicle
standards. Enhanced design innovation, reduced CO2 emissions
and increased fuel economy would likely result. This proposal would
facilitate the introduction of 48 volt mild hybrid technologies and
hydrogen fuel cell vehicles, and responds not only to GTR No. 13 but
also to petitions for rulemaking from Toyota and the Alliance.
    Petitioner Toyota believes that an additional compliance option
that includes elements of the physical barrier option in GTR No. 13 is
needed to allow hydrogen fuel cell vehicles (HFCVs) to be offered for
sale in the U.S.\2\ HFCVs and other electric powered

vehicles operate with their DC high voltage sources (e.g. high voltage
battery) connected to the AC high voltage sources (e.g. electric
motor). In a moderate to severe crash (e.g., crash speeds at which an
air bag would deploy), electric powered vehicles are generally designed
with an automatic disconnect mechanism that activates and breaks the
conductive link between the electrical energy storage system and the
rest of the power train. Under these crash conditions in which an
automatic disconnect mechanism activates, Toyota states that its HFCVs
would be able to meet the electrical safety requirements of FMVSS No.
305. However, in low speed crashes where the automatic disconnect
mechanism is not designed to activate so that the vehicle can be driven
away after a minor crash (fender-bender), Toyota states that its HFCVs
would not be able to meet the electrical safety requirements in FMVSS
No. 305. The petitioner believes that the additional compliance option
requested in its petition would solve this problem and would not cause
any reduction in the level of electrical safety now required by FMVSS
No. 305.
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    \2\ Subsequent to its submission of the petition for rulemaking,
Toyota submitted and was granted a temporary exemption from FMVSS
No. 305 for an HFCV (see grant of petition, January 2, 2015 (80 FR
101)). Toyota incorporates electrical protection barriers
(conductively connected to the electric chassis with low resistance)
and maintains at least a 100 ohms/volt electrical isolation into
their design. NHTSA granted the petition for exemption on the basis
that the exemption would make the development or field evaluation of
a low emission (zero emission) vehicle easier and would not
unreasonably reduce the safety of the vehicle.
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    Petitioner Alliance requests a physical barrier compliance option
to facilitate the production of 48 volt mild hybrid technologies as
well as hydrogen fuel cell vehicles. The petitioner asks NHTSA to amend
FMVSS No. 305 to adopt a physical barrier option incorporated in the
Society of Automotive Engineers (SAE) J1766 Jan 2014,\3\ section 5.3.4,
for 48 volt mild hybrid systems. The Alliance believes that the
provisions for physical barriers in section 5.3.4 incorporate the
requirements of GTR No. 13 and provide for physical barriers that
ensure equal levels of safety as that afforded by the current FMVSS No.
305 electrical safety requirements.
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    \3\ SAE J1766, ``Recommended practice for electric, fuel cell,
and hybrid electric vehicle crash integrity testing,'' January 2014,
SAE International, http://www.sae.org.
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    The petitioner states that while vehicles with 48 volt mild hybrid
systems use mostly low-voltage components that do not present any
danger of harmful electric shock, AC voltage sources contained within
the system can exceed the 30 volt threshold in FMVSS No. 305 for
consideration as a high voltage source. Since these systems are
grounded to the vehicle chassis, they cannot meet FMVSS No. 305's
existing electrical isolation option. The petitioner states that while
it is feasible to design a 48 volt mild hybrid system that is isolated
from the chassis and meets FMVSS No. 305's electrical isolation
requirements, such designs involve more complexity, higher consumer
costs, and higher mass resulting in reduced fuel economy and increased
emissions. The petitioner believes that these penalties are
inappropriate when there would be no incremental safety benefit gained
beyond that associated with SAE J1766's physical barrier option.
    NHTSA has undertaken this rulemaking after carefully and
extensively examining the safety issues. The agency previously decided
against consideration of a physical barrier option earlier in the
history of FMVSS No. 305, when our knowledge about the option was
limited.\4\ Commenters to an NPRM to upgrade electrical shock
protection requirements had asked NHTSA to adopt the option in the
final rule, for reasons similar to those provided by petitioners Toyota
and the Alliance. NHTSA declined, citing concerns about the lack of
notice for the provision, the absence of developed test procedures to
ensure protection from indirect contact, and uncertainty as to whether
the option would sufficiently account for indirect contact failure
modes. NHTSA then decided to undertake a research program (later known
as the Battelle study, discussed below in this preamble) to better
understand the issues related to a physical barrier option for
electrical safety.
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    \4\ See final rule, 75 FR 33515, June 14, 2010; response to
petitions for reconsideration, 76 FR 45436, July 29, 2011.
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    Since that decision in 2010, a number of developments led to
today's proposal. GTR No. 13 was established, a product of shared data
and knowledge from governing bodies and international experts around
the world. The Battelle study was completed and the physical barrier
countermeasure design was made more robust in response to its findings,
with SAE revising J1766 in January 2014 to set forth more protective
safety practices than it had before to address remote albeit lingering
concerns. Importantly, there have now been years of worldwide
recognition of the physical barrier option as an acceptable means of
providing electrical safety in electric powered vehicles, with years of
experience in design labs and in the field showing no evidence of
associated safety problems. HFCVs, 48 volt mild hybrid technologies,
and other vehicle designs have become a reality, and with them abundant
potential for the development of electrical technologies that a
physical barrier option in FMVSS No. 305 can facilitate, expedite and
safeguard.
    We estimate that adopting this NPRM would come at essentially no
cost to consumers in the U.S. This proposal closely mirrors the
electrical safety provisions of GTR No. 13, which have been implemented
by manufacturers in this country.
    NHTSA believes that this NPRM would improve the level of safety
afforded to the public. Adopting the provisions from GTR No. 13 that
reduce the risk of harmful electric shock during normal vehicle
operation would improve FMVSS No. 305 by expanding its performance
requirements beyond post-crash conditions. The proposed requirements
would provide post-crash compliance options for new power train
configurations that ensure that those configurations provide a
comparable level of post-crash safety compared to existing electric
vehicles.

Summary of Proposal

    The proposed amendments are summarized as follows. In furtherance
of implementing GTR No. 13 and in response to the petitions for
rulemaking--
    a. This NPRM proposes to add electrical safety requirements for
vehicle performance during everyday (``normal'') vehicle operations (as
opposed to during and after a crash), to mitigate electric shock due to
loss in electrical isolation and direct or indirect contact of high
voltage sources. The electrical safety requirements during normal
vehicle operations would include requirements for:

    1. Direct contact protection from high voltage sources

    i. IPXXD protection level \5\ for high voltage sources inside
passenger and luggage compartments. IPXXB protection level for high
voltage sources not in passenger and luggage compartments.
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    \5\ IPXXB and IPXXD ``protection levels'' refer to the ability
of the physical barriers to prevent entrance of a probe into the
enclosure, to ensure no direct contact with high voltage sources.
``IPXXB'' is a probe representing a small human finger. ``IPXXD'' is
a slender wire probe. Protection degrees IPXXD and IPXXB are
International Electrotechnical Commission specifications for
protection from direct contact of high voltage sources.
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    ii. IPXXB protection level for service disconnect that can be
opened or removed without tools.
    iii. Markings on barriers of high voltage sources that can be
physically accessed, opened, or removed without the use of tools.

    iv. Orange color outer covering for cables of high voltage
sources that are located outside electrical protection barriers.\6\
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    \6\ An electrical protection barrier is defined in GTR No. 13 as
the part providing protection from direct contact with high voltage
sources from any direction of access. These may be physical barriers
that enclose high voltage sources.

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    2. Indirect contact protection from high voltage sources

    Exposed conductive parts of electrical protection barriers would
have to be conductively connected to the chassis with a resistance
less than 0.1 ohms, and the resistance between two simultaneously
reachable exposed conductive parts of electrical protection barriers
that are within 2.5 meters of each other would have to be less than
0.2 ohms.

    3. Electrical isolation of high voltage sources

    i. 500 ohms/volt or higher electrical isolation for AC high
voltage sources and 100 ohms/volt or higher for DC high voltage
sources.
    ii. For conditions where AC and DC bus are connected, AC high
voltage sources would be permitted to have electrical isolation of
100 ohms/volt or higher, provided they also have the direct and
indirect contact protection described in 1 and 2, above.
    iii. There would be an exclusion of 48 volt hybrid vehicles from
electrical isolation requirements during normal vehicle operation.

    4. Electrical isolation monitoring system for DC high voltage
sources on fuel cell vehicles.
    5. Electrical safety during charging involving connecting the
vehicle to an external electric power supply:

    i. Minimum electrical isolation resistance of one million ohm of
the coupling system for charging the electrical energy storage
system; and
    ii. Conductive connection of the electric chassis to earth
ground before and during exterior voltage is applied.

    6. Mitigating driver error by--

    i. Requiring an indication to the driver when the vehicle is in
active driving mode upon vehicle start up and when the driver is
leaving the vehicle; and,
    ii. Preventing vehicle movement by its own propulsion system
when the vehicle charging system is connected to the external
electric power supply.

    b. This NPRM also proposes to amend FMVSS No. 305's post-crash
electrical safety requirements. The proposed post-crash electrical
safety requirements include:

    1. Adding an additional optional method of meeting post-crash
electrical safety requirements through physical barrier protection
from high voltage sources. The proposed specifications of this
optional method of electric safety include requirements ensuring
that:
    i. High voltage sources would be enclosed in barriers that
prevent direct human contact with high voltage sources (IPXXB
protection level),
    ii. Exposed conductive parts of electrical protection barriers
would be conductively connected to the chassis with a resistance
less than 0.1 ohms, and the resistance between any two
simultaneously reachable exposed conductive parts of electrical
protection barriers that are less than 2.5 meters from each other
would be less than 0.2 ohms, and
    iii. Voltage between a barrier and other exposed conductive
parts of the vehicle would be at a low voltage level that would not
cause electric shock (less than 60 VDC \7\ or 30 VAC).
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    \7\ VDC is the voltage for direct current sources and VAC is
voltage for alternating current sources.
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    2. Permitting an AC high voltage source that is conductively
connected to a DC high voltage source to meet lower minimum
electrical isolation requirement of 100 ohms/volt, provided the AC
high voltage source also has physical barrier protection specified
in 1, above.

II. FMVSS No. 305

    FMVSS No. 305 currently establishes requirements to reduce deaths
and injuries during and after a crash that occurs because of
electrolyte spillage from electric energy storage devices, intrusion of
electric energy storage/conversion device into the occupant
compartment, and electrical shock. Among other things, FMVSS No. 305
requires that during and after the crash tests specified in the
standard, high voltage sources in the vehicle must be either (a)
electrically isolated from the vehicle's chassis,\8\ or (b) their
voltage is below specified levels considered safe from electric shock
hazards.\9\
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    \8\ Under this electrical isolation option, since the
physiological impacts of DC are less than those of AC, the standard
permits DC high voltage sources with an electrical isolation
monitoring system to have lower minimum electrical isolation (100
ohms/volt) than the 500 ohms/volt required for AC high voltage
sources. This level of electrical isolation limits the current that
could pass through a human body (that is in contact with the
vehicle) to no more than 10 milliamperes (mA) DC or 2 mA AC. These
levels are considered to be safe levels of current and would not
cause any tissue damage, or fibrillation.
    \9\ Under this low voltage option, electrical components are
considered to be low voltage and safe from electric shock hazard if
their voltage is less than or equal to 60 VDC or 30 VAC.
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    Many of these electrical shock protection requirements were
established by a June 14, 2010 final rule (75 FR 33515) that revised
the standard to align it more closely with the April 2005 version of
SAE J1766. Commenters to the NPRM preceding the June 14, 2010 final
rule (viz., the Alliance and Global Automakers) requested another
electrical safety compliance option, called the ``physical barrier
option,'' for providing greater flexibility to allow introduction of
advanced power train technologies. In the physical barrier option, high
voltage sources are enclosed in physical barriers (electrical
protection barriers) that do not permit entrance of a finger probe into
the enclosure after the crash test to ensure no direct contact with
high voltage sources. This option also requires the physical barriers
to be conductively connected to the electric chassis to ensure no
electric shock due to indirect contact in the event of loss in
isolation of a high voltage source.
    In the June 14, 2010 final rule, NHTSA declined to adopt the
physical barrier option, citing concerns about the sufficiency of
notice provided for the provision, the absence of developed test
procedures to ensure protection from indirect contact, and uncertainty
as to whether the option would sufficiently account for indirect
contact failure modes. NHTSA stated that it would undertake a research
program (the Battelle study) to better understand the issues related to
a physical barrier option for electrical safety.

III. The Global Technical Regulation

a. Overview of the Process

    The United States is a contracting party to the ``1998 Agreement''
(the Agreement concerning the Establishing of Global Technical
Regulations for Wheeled Vehicles, Equipment and Parts which can be
fitted and/or be used on Wheeled Vehicles). This agreement entered into
force in 2000 and is administered by the UN Economic Commission for
Europe's (UN ECE's) World Forum for the Harmonization of Vehicle
Regulations (WP.29). The purpose of this agreement is to establish
Global Technical Regulations (GTRs).
    GTR No. 13, ``Hydrogen fuel cell vehicles,'' addresses hydrogen
fuel cell vehicle technology. NHTSA closely collaborated with experts
from contracting parties to the 1998 Agreement, particularly Germany
and Japan, to develop a GTR for hydrogen fueled vehicles that would
establish levels of safety that are equivalent to or exceeds those for
conventional gasoline fueled vehicles. The collaborative effort in this
process led to the establishment of GTR No. 13 in June 2013.
    The U.S. voted on June 27, 2013 in favor of establishing GTR No.
13. In voting yes to establishing the GTR, NHTSA is obligated to
``submit the technical Regulation to the process'' used in the U.S. to
adopt the requirement into our law or regulation. By issuance of this
NPRM, NHTSA is initiating the process for considering adoption of GTR
No. 13.

    Under the terms of the 1998 Agreement, NHTSA is not obligated to
adopt the GTR after initiating this process. In deciding whether to
adopt a GTR as an FMVSS, we follow the requirements for NHTSA
rulemaking, including the Administrative Procedure Act, the National
Highway and Motor Vehicle Safety Act (Vehicle Safety Act), Presidential
Executive Orders, and DOT and NHTSA policies, procedures and
regulations. Among other things, FMVSSs issued under the Vehicle Safety
Act ``shall be practicable, meet the need for motor vehicle safety, and
be stated in objective terms.'' 49 U.S.C. 30111.
    This NPRM does not propose the entirety of GTR No. 13 at this time.
This document only addresses the electrical safety requirements in GTR
No. 13 (i.e., the electrical isolation requirements, physical barrier
requirements, etc.). GTR No. 13 also addresses hydrogen fuel system and
fuel container integrity requirements and the agency's plan is to issue
a separate proposal to seek comment on incorporating those portions of
GTR No. 13 into the relevant FMVSSs.

b. Overview of GTR No. 13

    Hydrogen fueled fuel cell vehicles have an electric drive-train
powered by a fuel cell that generates electric power electrochemically
using hydrogen. The hydrogen is electrochemically combined with oxygen
(from air) within the fuel cell system to produce high-voltage electric
power. The electric power is supplied to the electric drive motors and/
or used to charge batteries and capacitors. HFCVs may also be equipped
with batteries to supplement the output of fuel cells and may also
recapture energy during stopping through regenerative braking, which
recharges batteries and thereby improves efficiency.
    The fuel cell provides DC power while the drive motors typically
operate on AC. Therefore, the power train has: (a) Inverters to convert
DC power to AC to run the motors and (b) converters to convert AC power
generated in the drive motor during regenerative braking to DC to store
energy in the batteries. In many respects, the electric power train of
an HFCV is similar to that of electric and hybrid electric vehicles.
GTR No. 13, in part, specifies electrical safety requirements during
normal vehicle operation and after a crash test, to protect against
electric shock in the event of a failure in the high voltage propulsion
system.
    In general, the portions of GTR No. 13 that are relevant to this
rulemaking are the electric safety requirements intended to protect
against the potential for electric shock during (a) normal vehicle
operation, and (b) after a crash. We discuss these requirements in GTR
No. 13 in the sections below.
1. Electric Safety Requirements During Normal Vehicle Operation
    These performance requirements in GTR No. 13 are requirements
intended for protecting vehicle occupants (and others that may interact
with the vehicle) against electric shock during normal vehicle
operation.\10\ For the purposes of the GTR, normal vehicle operations
include those during driving and charging.
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    \10\ In other words, the focus of this ``in-use'' testing
(unlike ``post-crash'' testing, discussed later) deals with
performance criteria that would be assessed without first exposing
the vehicle to a crash test. This testing is aimed at evaluating
what the performance of the vehicle would be under normal operating
conditions.
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    The GTR requirements apply to all high voltage sources (electric
components contained or connected to the electric power train that have
a working voltage greater than 30 VAC or 60 VDC). It requires these
high voltage sources to have all four of the following measures to
protect against electric shock during normal vehicle operations: (1)
Prevent direct contact of high voltage sources (those operating with
voltage greater than 30 VAC or 60 VDC); (2) prevent indirect contact of
high voltage sources; (3) electrically isolate the high voltage sources
from the electric chassis (500 ohms/volt or higher for AC and 100 ohms/
volt or higher for DC sources); and (4) electrical isolation monitoring
system for HFCVs that warns the driver in the event of loss in
isolation.
    The GTR also has the following measures to reduce driver errors
that may result in potential unsafe conditions: (1) Indication to the
driver when the vehicle is in possible active driving mode at startup
and when the driver is leaving the vehicle, and (2) prevent vehicle
movement by its own propulsion system when the vehicle charging system
is connected to the external electric power supply.
Protection Against Direct Contact With High Voltage Sources
    For protection against direct contact with high voltage sources,
the GTR has different requirements based on the location of the high
voltage source (i.e., if it is in the passenger or luggage compartment
of the vehicle or not).
    The GTR requires high voltage sources inside the passenger
compartment or luggage compartment to be enclosed in protection systems
such as solid insulators, electrical protection barriers, and
enclosures that cannot be opened, disassembled, or removed without the
use of tools and that provide protection degree IPXXD. Protection
degree IPXXD is an International Electrotechnical Commission (IEC)
specification for protection from direct contact of high voltage
sources. IPXXD protection is verified when a standard probe (rigid test
wire shown in Figure 1), 100 millimeters (mm) long and 1 millimeter
(mm) in diameter, does not contact high voltage components when probed
to enter an electrical protection barrier or enclosure.\11\
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    \11\ IEC60529 Second edition 1989-11 + Am. 1 1999-11, EN60529,
``Degrees of protection provided by enclosures.''
[GRAPHIC] [TIFF OMITTED] TP10MR16.000

    For high voltage sources not in passenger or luggage
compartments,\12\ the GTR requires that they be enclosed in protection
systems such as solid insulators, electrical protection barriers, and
enclosures that cannot be opened, disassembled, or removed without the
use of tools, and that provide a protection degree of IPXXB (as opposed
to IPXXD, referenced above). Protection degree IPXXB is an IEC
specification for protection from direct contact of high

voltage sources. IPXXB protection is verified when a standard probe
(resembling a small human finger), 80 mm long and 12 mm in diameter,
does not contact high voltage components when probed to enter an
electrical protection barrier or enclosure.\13\ (See Figure 2 below.)
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    \12\ GTR No. 13 specifies direct contact protection requirements
for high voltage connectors (including vehicle inlet) separately.
    \13\ IEC60529 Second edition 1989-11 + Am. 1 1999-11, EN60529,
``Degrees of protection provided by enclosures.'' This test probe
designed to simulate a small human finger (12 mm) conforms to ISO
20653 ``Road vehicles--Degrees of protection (IP-Code)--Protection
of electrical equipment against foreign objects, water, and access
(IPXXB).''
[GRAPHIC] [TIFF OMITTED] TP10MR16.001

    In addition to barriers preventing direct physical contact with
high voltage sources, GTR No. 13 also requires protections for the
``service disconnect.'' \14\ These provisions protect emergency
personnel, persons performing service/maintenance on the vehicle, and
vehicle occupants. The GTR requires that a service disconnect (which
can be opened, disassembled or removed without tools) be enclosed by
protection systems with protection degree IPXXB when the service
disconnect is opened, disassembled, or removed.
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    \14\ A service disconnect is a device for deactivation of an
electrical circuit when conducting checks and services of the
electric battery, fuel cell stack, or other high voltage sources.
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    Further, the GTR requires that high voltage sources be labeled
using the symbol shown in Figure 3, below. The interior of the symbol
is yellow and the border and arrow symbol are black. This requirement
aims to provide a standardized warning regarding the presence of high
voltage sources within an enclosure that can be physically accessed,
opened or removed without the use of tools. The GTR specifies that the
labels need to be on or near electric energy storage/conversion devices
and on electrical protection barriers or enclosures of high voltage
sources that can be physically accessed, opened, or removed without the
use of tools and that are not located underneath the vehicle floor. For
connecters of high voltage sources, the GTR makes this requirement
optional.
[GRAPHIC] [TIFF OMITTED] TP10MR16.002

    In the same vein, the GTR requires cables to have a standardized
warning that high voltage cables are present. The GTR requires that
cables for high voltage sources, which are not located within
enclosures, must have an orange outer covering for identification.
Protection Against Indirect Contact With High Voltage Sources
    Indirect contact of high voltage sources \15\ may occur when a high
voltage source experiences a loss in electrical isolation and the
physical barrier or enclosure gets electrically energized. This type of
contact could also lead to electrical shock. To address this concern,
the GTR requires, first, that exposed conductive parts (parts which may
become electrically energized under electrical isolation failure and
which can be contacted by a human, such as electrical protection
barriers and enclosures) be conductively connected to the electrical
chassis such that the resistance between all exposed conductive parts
and the electrical chassis is less than 0.1 ohms when there is current
flow of at least 0.2 amperes (A).\16\ This would ensure that in the
event of loss in electrical isolation, no dangerous voltage potentials
are produced between exposed conductive parts and the electrical
chassis, and therefore very low levels of current would flow through a
human body contacting different parts of the vehicle.\17\
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    \15\ Contact of a conductive part which is energized due to loss
in electrical isolation of a high voltage source is an indirect
contact of the high voltage source.
    \16\ GTR No. 13 considers this requirement to be met if visual
inspection indicates that a conductive connection has been
established by welding. NHTSA has concerns about this provision and
is requesting comments on it.
    \17\ Since current flows through the path of least resistance,
most of the current flow would be through the chassis rather than
through the human body which has a significantly higher resistance.
---------------------------------------------------------------------------

    Second, GTR No. 13 requires that vehicles whose rechargeable energy
storage systems are charged by conductively connecting to an external
grounded electric power supply have a device that conductively connects
the electrical chassis to the earth ground during charging. This
ensures that if there is a loss in electrical isolation of a high
voltage source during charging and the vehicle chassis is contacted by
a human, the magnitude of current

flowing through the person is very low and in the safe zone.\18\
---------------------------------------------------------------------------

    \18\ Current will flow through the path of least resistance and
therefore most of the current resulting from a loss of electrical
isolation would flow through the ground connection rather than
through the human body.
---------------------------------------------------------------------------

Protection by Electrical Isolation
    GTR No. 13 affords different electrical isolation requirements for
AC and DC high voltage sources based on whether they are conductively
isolated from each other or conductively linked together.
    For AC and DC high voltage sources that are conductively isolated
from each other, GTR No. 13 requires isolation resistance between the
high voltage source and the electrical chassis to be a minimum value of
100 ohms/volt of the working voltage for DC high voltage sources, and a
minimum value of 500 ohms/volt of the working voltage for AC high
voltage sources. This requirement is similar to the post-crash
electrical isolation requirement currently in FMVSS No. 305. It ensures
that in the event high voltage sources are contacted, the current
flowing through the body is less than or equal to 10 mA DC or 2 mA AC--
which is considered to be safe.\19\
---------------------------------------------------------------------------

    \19\ See IEC TS 60479-1 and TS 60479-2 Effects of Current on
Human Beings and Livestock--Part 1: General Aspects, 2005-07,
Reference Nos. CEI/IEC/TS 60479-1:2005.
---------------------------------------------------------------------------

    For AC and DC high voltage sources that are conductively connected,
GTR No. 13 affords two options. The first option is the vehicle may
maintain an isolation resistance between the high voltage sources and
the electrical chassis at no less than 500 ohms/volt of the working
voltage. The second option is it may provide an isolation resistance
between the high voltage sources and the electrical chassis of no less
than 100 ohms/volt of the working voltage and provide physical barrier
protection for the AC high voltage sources to prevent both direct and
indirect contact, as discussed above. (Note that a ``physical barrier''
approach would be a new concept in FMVSS No. 305.)
    In addition, GTR No. 13 specifies electrical isolation requirements
for charging electric vehicles whose rechargeable energy storage system
are charged by conductively connecting to an external power supply. GTR
No. 13 requires that the isolation resistance between the electrical
chassis and high voltage sources conductively connected to the vehicle
inlet which connects to the external power supply to be at least 1
million (M) ohms when the charge coupler is disconnected. This
requirement is in accordance with IEC61851-1-2010 \20\ and
International Standards Organization (ISO) 6469-2 \21\ which prescribe
electrical isolation for electric vehicles that connect to the power
grid for charging. A typical minimum allowable isolation requirement
for a grounded product connected to the power grid is 1000 ohms/volt,
which computes to 1M ohms.
---------------------------------------------------------------------------

    \20\ IEC 61851-1:2010 Electric vehicle conductive charging
system--Part 1: General requirements, available at https://webstore.iec.ch/publication/6029.
    \21\ ISO 6469-2:2009 Electrically propelled road vehicles--
Safety specifications--Part 2: Vehicle operational safety means and
protection against failures. Available at http://www.iso.org/iso/catalogue_detail?csnumber=45478.
---------------------------------------------------------------------------

Protection by Electrical Isolation Monitoring System
    GTR No. 13 also contains provisions for monitoring the electrical
isolation under certain conditions. In fuel cell vehicles, GTR No. 13
requires DC high voltage sources (other than the coupling system for
charging) to have an on-board electrical isolation monitoring system,
together with a warning to the driver if the isolation resistance drops
below the minimum required value of 100 ohms/volt. FMVSS No. 305
specifies a similar requirement except that FMVSS No. 305 applies this
provision to vehicles that are certified to the 100 ohms/volt
electrical isolation option \22\ (rather than to fuel cell vehicles
specifically).
---------------------------------------------------------------------------

    \22\ As discussed above, AC high voltage sources are required
under FMVSS No. 305 to have at least 500 ohms/volt of electrical
isolation. DC high voltage sources may have an electrical isolation
of 100 ohms/volt or greater provided that they meet conditions such
as having an electrical isolation monitoring system meeting the
requirements of the standard.
---------------------------------------------------------------------------

Protection by Mitigating Driver Error
    GTR No. 13 also has provisions for mitigating the likelihood of
driver error in operating electric vehicles. First, GTR No. 13 requires
that at least a momentary indication be given to the driver when the
vehicle is in possible active driving mode.\23\ Second, when leaving
the vehicle, the driver shall be informed by an optical or audible
signal if the vehicle is still in possible active driving mode. The
third requirement is that for vehicles where the on-board rechargeable
energy storage/conversion device can be charged externally, vehicle
movement by its own propulsion system shall not be possible when the
external electric power supply is physically connected to the vehicle
inlet.
---------------------------------------------------------------------------

    \23\ I.e., the vehicle mode when application of pressure to the
accelerator pedal or release of the brake system causes the electric
power train to move the vehicle.
---------------------------------------------------------------------------

    The first requirement does not apply to vehicles with an internal
combustion engine that directly or indirectly provides the vehicle's
propulsion on startup. Since electric powered vehicles operate quietly,
an indication of the vehicle in possible active driving mode would
assist the driver in reducing operational errors that could have safety
implications. The third requirement prevents the charger from getting
ripped out of the vehicle inlet during charging that could cause
electrical arcing.
2. Electric Safety Requirements Post-Crash Test
    The post-crash \24\ electrical safety requirements in GTR No. 13
apply to all high voltage sources (electric components contained or
connected to the electric power train that have a working voltage
greater than 30 VAC or 60 VDC). GTR No. 13 does not specify the type of
crash test and how it is conducted. This is left to each contracting
party to develop appropriate crash tests. After the crash test, to
provide adequate protection against electric shock, GTR No. 13 affords
three potential options that a vehicle manufacturer may use to protect
against potential human contact with high voltage sources. GTR No. 13
specifically gives contracting parties the choice not to provide the
physical barrier option in their final domestic regulation.
---------------------------------------------------------------------------

    \24\ In terms of ``post-crash'' we are referring to assessing a
vehicle's electrical safety provisions (electrical isolation,
physical barrier, etc.) after the vehicle is exposed to specified
crash forces in a crash test. This is different from the
aforementioned ``in-use'' (or ``normal operating conditions'')
requirements where the vehicle is evaluated for conformance with a
performance requirement without first being exposed to crash
testing.
---------------------------------------------------------------------------

Reduce the Voltage Levels of the High Voltage Sources Such That They
Are No Longer High Voltage Sources
    Reducing the high voltage sources' voltage to a level below what is
considered a ``high voltage source'' means there is no further need to
protect against electrical shock from those sources. Thus, in this
option, GTR No. 13 requires that the voltages of each high voltage
source be reduced to less than or equal to 30 VAC or 60 VDC within 60
seconds after the impact. A version of this option for electrical
safety is currently in FMVSS No. 305.
Use a Physical Barrier and Other Techniques To Prevent Direct/Indirect
Contact \25\ With High Voltage Sources
---------------------------------------------------------------------------

    \25\ To reiterate, this option is one that contracting parties
may choose not to propose. In other words, a contracting party that
voted in favor of this GTR may submit this GTR to their domestic
rulemaking process affording only two options for protecting against
post-crash electrical shock (i.e., reducing the high voltage
sources' voltage so that they are no longer considered high voltage;
and maintaining the required levels of electrical isolation of the
high voltage sources).
---------------------------------------------------------------------------

    The physical barrier option protects against electrical shock by
preventing

any human contact (direct or indirect) with the high voltage sources.
The physical barrier option for post-crash is similar to the physical
barrier option that GTR No. 13 affords for its normal vehicle operation
requirement. The requirements state that (post-crash) the vehicle needs
to prevent both direct and indirect human contact with high voltage
sources through the use of: (1) Physical barriers (i.e., prevent a
finger probe test device from contacting any high voltage source); and
(2) low resistance conductive connection of the physical barriers to
the electrical chassis (i.e., the resistance between all exposed
conductive parts and the electrical chassis has to be less than 0.1
ohms when there is a current flow of at least 0.2 A \26\). The only
major difference is that GTR No. 13 uses protection degree IPXXB (i.e.,
the IPXXB finger probe) for its post-crash requirements (rather than
IPXXD).\27\ As noted earlier, FMVSS No. 305 currently contains no
similar provision for electric shock protection through physical
barriers.
---------------------------------------------------------------------------

    \26\ GTR No. 13 considers this requirement to be met if visual
inspection indicates that conductive connection has been established
by welding. The minimum resistance requirement is only evaluated in
case of doubt.
    \27\ Here the post-crash requirements in the GTR use IPXXB
because it is assumed unlikely that, post-crash, someone would use a
wire to probe the enclosure.
---------------------------------------------------------------------------

Electrically Isolate the High Voltage Sources
    This option protects against electric shock by ensuring that a
sufficient level of electrical isolation resistance is provided for the
high voltage source. GTR No. 13 provides two different sets of
requirements (based on whether the vehicle's AC and DC high voltage
sources are conductively connected) for vehicles electing to use this
option to protect against electric shock.
    If the AC and DC high voltage sources are conductively isolated
from each other, then the minimum electrical isolation of a high
voltage source to the chassis is 500 ohms/volt for AC components and
100 ohms/volt for DC components of the working voltage.
    If AC and DC high voltage sources are conductively connected, GTR
No. 13 requires that electrical isolation of AC and DC high voltage
sources be no less than 500 ohms/volt of the working voltage, or the
electric isolation of those sources be no less than 100 ohms/volt
provided that the AC high voltage sources (in addition to the minimum
100 ohms/volt electrical isolation) meet the reduced voltage level
requirements discussed above (first option), or meet the physical
protection requirements discussed above in the second option.
    We note that while currently FMVSS No. 305 contains different
requirements for AC high voltage sources and DC high voltage sources,
it does not distinguish requirements based on whether the AC and DC
high voltage sources are conductively linked. Thus, while the
requirements in GTR No. 13 for AC and DC sources that are not
conductively connected are the same as those currently in FMVSS No.
305, the alternative requirements for conductively connected AC and DC
sources are not.

c. How does this proposal differ from GTR No. 13?

    This NPRM proposes to add electrical safety requirements during
normal vehicle operation in GTR No. 13 into FMVSS No. 305. The proposal
also adds a modified version of physical barrier protection that is
specified in GTR No. 13 as a compliance option for meeting post-crash
electrical safety requirements. However, this NPRM does not propose to
adopt all the specifications in GTR No. 13. The differences in
electrical safety requirements and associated test procedures in the
proposal and that in GTR No. 13, along with an explanation for these
differences, are provided below. Comments are requested on NHTSA's
views.
Physical Barrier Protection During Normal Vehicle Operation
    This NPRM proposes to adopt GTR No. 13's physical barrier
protection requirement during normal vehicle operation for direct
contact. However, for indirect contact protection, we propose to use
the proposed post-crash indirect contact protection requirements
described above (which include two additional requirements described
above in addition to that specified in GTR No. 13).
Verification of Physical Barrier Protection During Normal Vehicle
Operations
    GTR No. 13 considers indirect contact protection requirements
during normal vehicle operations to be met if a galvanic connection
\28\ has been established by welding between exposed conductive parts
and the electrical chassis.
---------------------------------------------------------------------------

    \28\ A galvanic connection is a conductive connection.
---------------------------------------------------------------------------

    For conditions where the DC and AC high voltage sources are
connected during normal vehicle operations, GTR No. 13 permits the AC
high voltage sources to have a minimum electrical isolation of 100
ohms/volt provided the AC high voltage sources have either: (a) Double
or more layers of solid insulators or electrical protection barriers
that meet the requirements for indirect contact protection; or (b)
Mechanically robust protections that have sufficient durability over
vehicle service life such as motor housings, electronic converter cases
or connectors.
    These methods of verification consist of mere visual inspection and
do not provide sufficient objectivity for use in an FMVSS. Therefore,
the agency's proposal does not consider indirect contact protection
requirements to be met if galvanic connection has been established
between exposed conductive parts and the electric chassis. The agency
is also not proposing visual inspection methods to permit AC high
voltage sources that are connected to a DC high voltage source to have
minimum electrical isolation of 100 ohms/volt during normal vehicle
operation.
High Voltage Markings
    GTR No. 13 requires marking (yellow high voltage symbol) for
enclosures and barriers of high voltage sources (electrical protection
barriers) that can be physically accessed, opened, or removed without
the use of tools. These markings are not required for electrical
protection barriers located underneath the vehicle floor.
    NHTSA tentatively concludes that the exclusion is without merit.
GTR No. 13 does not provide a justification for exempting electrical
protection barriers located underneath the vehicle floor from the high
voltage marking requirement. There is also no definition of ``vehicle
floor'' in GTR No. 13. NHTSA does not believe electrical protection
barriers located under the vehicle floor should be excluded because it
is possible that the high voltage sources enclosed by these barriers
may be accessed in a rollover crash or during vehicle maintenance.
Direct Contact Protection of Connectors
    GTR No. 13 specifies direct contact protection requirements for
high voltage connectors separately. Per GTR No. 13, connectors do not
need to meet IPXXB protection if they are located underneath the
vehicle floor and are provided with a locking mechanism, or require the
use of tools to separate the

connector, or the voltage reduces to below 30 VAC or 60 VDC within one
second after the connector is separated. NHTSA does not believe
connectors of high voltage sources should be excluded. If connectors
are high voltage sources and if they can be accessed, opened, or
removed without the use of tools, regardless of whether they are
located under the floor, they should be required to meet the same
requirements for voltage markings and direct contact protection as
electric protection barriers. Additionally, the agency notes that
``vehicle floor'' and ``connector'' are not defined in GTR No. 13.
Therefore, NHTSA would not exclude connectors of high voltage sources.
Post-Crash Physical Barrier Protection Option
    GTR No. 13 specifies that individual contracting parties of the
1998 agreement may elect to propose the physical barrier protection
from direct and indirect contact of high voltage sources and live
parts. According to GTR No. 13, for protection against direct contact,
high voltage sources and live parts are required to have protection
degree IPXXB. For protection against indirect contact, GTR No. 13
requires that the resistance between all exposed conductive parts and
electrical chassis be lower than 0.1 ohm when there is current flow of
at least 0.2 A.
    The physical barrier protection option in this NPRM includes the
same provisions for direct and indirect contact protection as that in
GTR No. 13 but adds two additional requirements for indirect contact
protection (from SAE J1766 January 2014).
    This first additional requirement is that the resistance between
any two simultaneously reachable exposed conductive parts of the
electrical protection barriers that are less than 2.5 meters from each
other is less than 0.2 ohms. This additional requirement protects
against indirect contact of high voltage sources when two electrical
protection barriers are contacted simultaneously. The second additional
requirement is that the voltages between an electrical protection
barrier enclosing a high voltage source and other exposed conductive
parts are less than or equal to 30 VAC or 60 VDC. This additional
requirement is included in SAE J1766 January 2014 to provide additional
protection from indirect contact of high voltage sources, addressing
the issues raised in the Battelle research of the physical barrier
protection option.
Verification of Post-Crash Indirect Contact Protection
    GTR No. 13 states that a high voltage source is considered to have
post-crash indirect contact protection if the electrical protection
barrier enclosing the high voltage source has a galvanic connection to
the chassis by welding. This method of verification is a mere visual
inspection and lacks the objectivity needed for an FMVSS. This NPRM
does not include this method of verification and instead proposes to
use the test procedure in GTR No. 13 whereby a current of 0.2 A is
passed through the connection to determine its resistance.
Physical Barrier Protection of AC High Voltage Sources That Are
Connected to DC High Voltage Sources
    This NPRM proposes to adopt the physical barrier protection
requirement for direct contact specified in GTR No. 13 for both post-
crash and during normal vehicle operation. However, for indirect
contact protection, the proposal uses the proposed post-crash indirect
contact protection requirements described above (which include two
additional requirements described above in addition to that specified
in GTR No. 13).
Optional Procedures for Evaluating Electrical Isolation Post-Crash
    FMVSS No. 305's test procedure for measuring electrical isolation
of high voltage sources is similar to that in GTR No. 13. However, GTR
No. 13 permits the crash tests to be conducted without energizing the
electric power train while FMVSS No. 305 does not. In conditions where
the high voltage sources are not energized during the crash test, GTR
No. 13 permits measuring electrical isolation resistance of high
voltage sources by other means, including using a megohmmeter.\29\ Yet,
GTR No. 13 does not specify a test procedure to measure isolation
resistance using a megohmmeter.
---------------------------------------------------------------------------

    \29\ A megohmmeter is a specialized ohmmeter that is primarily
used to determine electrical isolation resistance. This device
operates by applying a voltage or current to the item being tested.
Because externally applied voltages or currents can disrupt its
measurement (and/or cause damage to the instrument) the megohmmer is
used to test items that are under an inactive and fully de-energized
state.
---------------------------------------------------------------------------

    NHTSA is not proposing to conduct the crash test without energizing
the electric power train and so is not permitting the use of the
megohmmeter. NHTSA stated its position on this matter in final rules
published on June 14, 2010 (75 FR 33515), July 29, 2011 (76 FR 45436),
and January 16, 2015 (80 FR 2320). In the January 16, 2015 final rule,
NHTSA noted that the agency's research on the feasibility of using a
megohmmeter for measuring electrical isolation presented certain
technical questions that need to be resolved (i.e., the research showed
that megohmmeters could accurately measure electrical isolation
resistance of DC high voltage sources in an inactive state but did not
consistently do so for AC high voltage sources).
    Additionally, electrical isolation resistance measurement with a
megohmmeter is only possible when the electrical power train is not
energized, such as when an inert gas is used in hydrogen containers of
a fuel cell vehicle. NHTSA will address the issue of the use of inert
gas in hydrogen containers of fuel cells vehicles when conducting crash
tests in a future proposal to incorporate into FMVSSs the fuel system
and fuel container integrity requirements of hydrogen fuel cell
vehicles in GTR No. 13. The agency will address in that rulemaking the
use of alternative methods of measuring isolation resistance in
conditions where the electric power train is not energized in crash
tests.
Procedures for Measuring Voltage Post-Crash
    FMVSS No. 305 specifies that all post-crash voltage measurements
for determining voltage and electrical isolation of high voltage
sources with respect to the electric chassis be made after a minimum of
5 seconds after the vehicle comes to rest following impact. GTR No. 13
specifies that for determining post-crash electrical isolation of high
voltage sources, the voltage measurements be made after a minimum of 5
seconds after ``impact.'' GTR No. 13 also specifies that for
determining post-crash voltage (for assessing compliance with the low
voltage option), the voltage measurements be made after a minimum of 5
seconds and no later than 60 seconds after impact.
    The agency is not proposing to change the timing of voltage
measurement post-crash in FMVSS No. 305 to harmonize with GTR No. 13.
The ``after impact'' interval specified in GTR No. 13 appears less
objective than FMVSS No. 305's measure and adopting the GTR No. 13
specified time for post-crash voltage measurement may reduce the
objectivity of the test. Further, all-in-all we believe this difference
in the timing of voltage measurement in FMVSS No. 305 and GTR No. 13 is
minor.

Miscellaneous Differences Between the Proposed Regulatory Text and GTR
No. 13
    There is some unnecessary or redundant text in some sections of GTR
No. 13 that we have not included in this proposal, to make the
regulatory text more concise. An example of this is in the electrical
isolation option for post-crash electrical safety, under conditions
when the AC and DC high voltage sources are connected. GTR No. 13
specifies that the vehicle meet one of the following requirements: (1)
Electrical isolation of the DC and AC high voltage sources from the
chassis be no less than 500 ohm/volt; (2) electrical isolation of the
DC and AC high voltage sources from the chassis be no less than 100
ohm/volt and the AC high voltage sources also have physical barrier
protection; or (3) electrical isolation of the AC and DC high voltage
sources from the chassis be no less than 100 ohm/volt and the AC high
voltage source is considered as a low voltage source. We believe that
the option (3) requirement above is unnecessary, because if the AC high
voltage source is considered as a low voltage source, it already meets
the low voltage electrical isolation option. Thus, we determined it is
not necessary to provide option (3).

IV. Battelle Study and Developments

    NHTSA initiated a research program in 2010, using Battelle as a
contractor, to better understand the safety implications of using a
physical barrier to protect against electric shock. The objectives of
the research were to: (a) Determine failure modes associated with
electrical protection barriers that could potentially result in
electric shock to occupants in the vehicle or to rescue workers due to
direct or indirect contact, (b) evaluate the practicability and
feasibility of test procedures in what was then a draft version \30\ of
GTR No. 13 for direct and indirect contact protection.
---------------------------------------------------------------------------

    \30\ The electrical safety requirements in the 2010 draft
version of GTR No. 13 are the same as those in the GTR No. 13 that
was established on June 27, 2013. Henceforth, we refer to the draft
version as the adopted GTR.
---------------------------------------------------------------------------

    As discussed below (and in our supporting technical document) \31\
the Battelle research indicates that the physical barrier protection
specified in GTR No. 13 would protect against electric shock when there
is a single point failure in the electrical safety systems. However, if
there were multiple failures in the electrical safety systems specified
in GTR No. 13 for normal vehicle operating conditions,\32\ the Battelle
research indicates that a person could receive an electric shock when
they contact the high voltage sources in certain specific ways.
---------------------------------------------------------------------------

    \31\ Along with this document, we have placed in the docket a
supporting technical document providing further information on our
analysis of the Battelle research and GTR No. 13.
    \32\ Under GTR No. 13, during normal vehicle operation, all high
voltage sources contained or connected to the power train are
required to be electrically isolated from the chassis (with minimum
electrical isolation of 500 ohms/VAC or 100 ohms/VDC) and enclosed
by physical barriers that prevent direct human contact. The physical
barriers enclosing these high voltage sources are required to be
conductively connected to the chassis (with resistance less than 0.1
ohms) to provide indirect contact shock protection.
---------------------------------------------------------------------------

    The Battelle study \33\ identified various scenarios of electrical
safety system failures, including direct contact of high voltage
source, indirect contact of live parts of high voltage sources, loss in
conductive connection between electrical protection barrier and
chassis, and a combination of these failures. Direct contact of a high
voltage source could occur in the event of a crash that results in
mechanical failure of protection barriers or penetration of electrical
insulation that would allow fingers or conductive tools to enter
protection barriers and contact the high voltage sources within the
barrier. Indirect contact of high voltage sources could occur in the
event of a crash in which an electrical protection barrier is energized
due to loss in electrical isolation of the high voltage source within
the barrier.
---------------------------------------------------------------------------

    \33\ Hydrogen Fuel Cell Vehicle--Electrical Protective Barrier
Option, Final Report, DOT HS 812134, May 2015. Available at http://www.nhtsa.gov/Research/Crashworthiness/Alternative%20Energy%20Vehicle%20Systems%20Safety%20Research and in
the docket for this NPRM.
---------------------------------------------------------------------------

    To illustrate failure modes associated with electric protection
barriers, Battelle used the schematic shown in Figure 4 below in which
a high voltage source (shown on the left side of the figure) is
isolated from the vehicle chassis by resistances RiH and
RiL on the positive and negative side, respectively, and
enclosed in an electrical protection barrier (EPB1). The
high voltage source may be either DC or AC and may represent a variety
of components such as a fuel cell, battery, motor, or capacitor.
    Also shown in Figure 4 are electrical wirings from the positive
side of the high voltage source to its negative side to complete the
circuit. The schematic shows two electric protection barriers
(EPB2 and EPB3) enclosing the wirings on the
positive and negative side, respectively, and a body with resistance
Rb contacting these two protection barriers. All three
electrical protection barriers in the figure are conductively connected
to the electrical chassis with resistances RCh,
RChH, and RChL.
    For normal vehicle operation, GTR No. 13 requires RiH
and RiL resistances to provide electrical isolation of at
least 500 ohms/VAC or 100 ohms/VDC. It also requires the electrical
wiring to be insulated. Further, it requires the three electrical
protection barriers (EPB1, EPB2, and
EPB3) to have protection degree IPXXD or IPXXB and be
conductively connected to the chassis such that the resistances
RCh, RChH, and RChL are less than 0.1
ohms. The lowest possible value of body resistance Rb is 500
ohms.\34\
---------------------------------------------------------------------------

    \34\ IEC TC-60479-I, ``Effects of current on human beings and
livestock--Part I--General Aspects,'' 2005.

---------------------------------------------------------------------------

[GRAPHIC] [TIFF OMITTED] TP10MR16.003

    Battelle's analysis of the schematic in Figure 4 identified
scenarios of direct contact and indirect contact of high voltage
sources. Direct contact occurs when the electrical protection barriers
EPB2 and/or EPB3 are breached or penetrated and
the body contacts the wiring enclosed within. Indirect contact occurs
when EPB2 and/or EPB3 are energized due to loss
of electrical isolation of the high voltage source within the barrier
and the body contacts the electrical protection barriers as shown in
Figure 4. Examples of direct and indirect contact scenarios are
presented below:
     Case 1--Direct contact of high voltage source without
electric shock hazard. Protection barrier EPB2 is
compromised and the body directly contacts the electrical wiring from
the positive side, and also contacts the electrical protection barrier
EPB3 enclosing the wiring on the negative side of the high
voltage source (Figure 5). In this case, as long as the resistance
RiL or RiH is greater than or equal to 500 ohms/
VAC or 100 ohms/VDC, the current through the body (shown by dashed
lines) will be within safe limits.
[GRAPHIC] [TIFF OMITTED] TP10MR16.004

     Case 2--Direct contact of a high voltage source with
electric shock hazard. Electrical protection barriers EPB2
and EPB3 of the wiring on the positive and negative side of
the high voltage source are compromised and the body contacts the
positive and negative wiring (Figure 6). For the worst Case 2
condition, a body resistance Rb equal to 500 ohms (lowest
possible) is used. For a DC high voltage source of 350V, the minimum
resistance value for RiL and RiH is 35,000 ohms.
Since the body resistance Rb is significantly lower than the
electrical isolation RiL and RiH,

current through the body (shown by dashed lines) is not limited and the
body would experience electric shock.
[GRAPHIC] [TIFF OMITTED] TP10MR16.005

     Case 3--Indirect contact of high voltage source without
electric shock hazard. The wiring on the positive side of the high
voltage source loses electrical isolation to the electrical protection
barrier, EPB2, and the body contacts the electrical
protection barriers EPB2 and EPB3 of the positive
and negative wiring (Figure 7). Similar to Case 1, as long as the
isolation resistance RiL or RiH is greater than
or equal to 500 ohms/VAC or 100 ohms/VDC, the current through the body
(shown by dashed lines) will be within safe limits.
[GRAPHIC] [TIFF OMITTED] TP10MR16.006

     Case 4--Indirect contact of high voltage source with
possibility of electric shock. The electric wiring of the positive and
negative sides of the high voltage source lose electrical isolation to
the protective barriers EPB2 and EPB3,
respectively, and the body contacts the two protective barriers
EPB2 and EPB3 (Figure 8). Since RCh,
RChH and RChL are all very low values (less than
0.1 ohms according to GTR No.13), this condition would result in a
short circuit of the high voltage source that could activate and open a
short circuit fuse that is generally equipped in electric

propulsion vehicles. If a fuse activates, then no current will flow and
so no electrical shock would occur. However, if the fuse does not
activate, and if the electrical isolation RiL and
RiH are reduced to low levels and the chassis resistance is
not significantly low compared to the body resistance, then the current
through the body contacting the protective barriers (shown by dashed
line) may not be within safe limits and the body could experience
electric shock. This scenario is further discussed in the Alliance
petition for rulemaking (infra) and in the supporting technical
document of this NPRM.
[GRAPHIC] [TIFF OMITTED] TP10MR16.007

    Battelle identified additional scenarios, including those regarding
loss in electrical isolation RiL and/or RiH and
loss of electrical bonding of the protective barriers with the
chassis.\35\ These scenarios showed that, for vehicles that meet the
electrical isolation and physical barrier protection requirement in GTR
No. 13 during normal vehicle operation, electric shock is not possible
when there is only a single point of failure in the electrical safety
systems. However, electric shock is possible when at least two or three
failures of electrical safety systems occur and a human body comes into
contact with two compromised protective barriers on opposite sides of
the high voltage source to complete the circuit. For example, in Case
2, electric shock could occur if two electrical protection barriers on
the positive and negative side of the high voltage source are
compromised and a body contacts the positive and negative side of a
high voltage source by entering the two compromised protection
barriers. In Case 4, electric shock could occur only if at least four
electric safety features (loss in electrical isolation of electrical
protection barriers EPB2 and EPB3 which are on the positive and
negative side of the high voltage source and loss in electrical
isolation RiH and RiL of the high voltage source) are compromised and
the body contacts both compromised barriers, EPB2 and EPB3.
---------------------------------------------------------------------------

    \35\ Details of these scenarios are presented in the Battelle
final report, DOT HS 812 134, May 2015, which is available in the
docket of this NPRM.
---------------------------------------------------------------------------

    To address the concern of electric shock from indirect contact, GTR
No. 13 specifies that the physical barriers enclosing high voltage
sources should be conductively connected with low resistance (less than
0.1 ohms) to the electrical chassis, so that if one segment of the high
voltage source should lose electrical isolation, all contactable
surfaces of the vehicle chassis and protective barriers will be at the
same voltage and thereby prevent electric shock to a person touching
two different protective barriers or parts of the electrical chassis.
    Battelle also evaluated the maximum resistance (0.1 ohms) of the
electric bonds between electrical protection barriers and the
electrical chassis that is specified in GTR No. 13. Battelle found that
in the event of multiple electrical safety system failures (loss in
electrical isolation of both segments of the high voltage source to
their electrical protection barriers) and a person touching both the
barriers to complete the circuit, the resistance of 0.1 ohms between
the protective barrier and electrical chassis would not be sufficient
to prevent electric shock to the person contacting the protective
barriers.\36\
---------------------------------------------------------------------------

    \36\ This issue is further explained in the supporting technical
document in the docket of this NPRM.
---------------------------------------------------------------------------

V. Toyota Petition for Rulemaking

    On December 23, 2013, Toyota submitted a petition for rulemaking to
amend FMVSS No. 305 by adding an additional compliance option for
electrical safety to allow HFCVs to be offered for sale in the US.
Toyota notes that the requested compliance option includes elements of
the electrical protection barrier that is currently in GTR No. 13.
Toyota notes that many countries, including the European Union, Japan,
and South Korea, already include electrical protection barrier as a
compliance option for electrical safety in their standards.
    Toyota explains its reasons for petitioning as follows.\37\ FMVSS
No. 305

requires compliance with electrical safety requirements following
impacts ``at any speed up to and including'' the specified test speeds.
Toyota notes that for electric powered vehicles, including fuel cell
vehicles, the DC high voltage sources (e.g. high voltage battery) will
be connected to the AC high voltage sources (e.g. electric motor)
during normal vehicle operation and in low speed crashes where the
automatic disconnect does not operate.\38\ In such conditions, when the
AC and DC high voltage sources are connected, the isolation resistance
at the AC high voltage source is in parallel with the isolation
resistance of the DC high voltage source. Therefore, even if the
electrical isolation provided for the AC high voltage source is
significantly greater than the required 500 ohms/volt, the effective
isolation resistance measured at the AC high voltage source can be, at
most, as high as that provided for the DC high voltage source.
---------------------------------------------------------------------------

    \37\ Honda Motor Co. Ltd. and American Honda Motor Co. Inc.
(Honda) echoed these concerns in its comments on NHTSA's notice of
receipt of Toyota's exemption petition, supra. See Docket No. NHTSA-
2014-0068.
    \38\ Toyota noted that the automatic disconnect mechanism is not
activated in low speed crashes, such as minor fender benders that
may occur in a parking lot and in conditions where the inverters in
the fuel cell auxiliary system may continue to operate.
---------------------------------------------------------------------------

    Toyota explains that in current battery electric vehicles,
manufacturers are able to provide electrical isolation for the high
voltage battery in excess of 500 ohms/volt, even though FMVSS No. 305
permits DC high voltage sources to have 100 ohms/volt with an
electrical isolation monitoring system. On the other hand, it is
difficult to maintain electrical isolation greater than 500 ohms/volt
for the fuel cell stack in an HFCV due to the presence of fuel cell
coolant.\39\ Therefore, when the DC and AC high voltage sources are
connected in an HFCV, it may not be possible to achieve the required
500 ohms/volt electrical isolation for AC high voltage sources.
---------------------------------------------------------------------------

    \39\ The fuel cell coolant may get ionized during repeated
operation and may reduce the electrical isolation provided.
---------------------------------------------------------------------------

    Toyota states that NHTSA said in the June 14, 2010 final rule (75
FR 33515) that the agency was issuing the final rule to facilitate the
development and introduction of fuel cell vehicles. One provision
provided by the final rule was to specify lower minimum electrical
isolation requirements for DC than AC high voltage sources (500 ohms/
volt for AC and 100 ohms/volt for DC sources). Toyota further asserts
that this flexibility offered for HFCVs is not useful unless a
provision is made for the condition when the AC and DC high voltage
sources are connected, such as after a low speed crash.\40\ Since such
a provision is currently not available, HFCVs are essentially required
to provide electrical isolation levels at or in excess of 500 ohms/volt
at the fuel cell stacks.
---------------------------------------------------------------------------

    \40\ FMVSS No. 305 requires that the electrical safety
requirements in FMVSS No. 305 be met after front, rear, and side
crash tests that include low speeds. In such conditions (which
includes ``fender benders''), the automatic disconnect is designed
to remain closed so that the vehicle remains operational and so the
driver can continue driving the vehicle.
---------------------------------------------------------------------------

    Toyota asks that NHTSA adopt an alternative provision for
electrical safety through isolation of high voltage sources that
involves electrical protection barriers to address post-crash
conditions where the AC and DC high voltage sources are connected. The
petitioner suggests adopting GTR No. 13's specification that the
electrical isolation of the high voltage source may be greater or equal
to 100 ohms/volt for an AC high voltage source if that AC source is
conductively connected to a DC high voltage source, provided that the
AC high voltage source meets the specified post-crash physical barrier
protection requirements in GTR No. 13.\41\ The petitioner suggests
specific regulatory text for the requirements and test procedures that
are based on the specifications in GTR No. 13 for modifying FMVSS No.
305 to include the petitioner's requested compliance option.
---------------------------------------------------------------------------

    \41\ The requirements for post-crash physical barrier protection
option for electrical safety in GTR No. 13 are that after a crash
test, high voltage sources have protection level IPXXB and that the
resistance between all exposed conductive parts and the electrical
chassis be lower than 0.1 ohm when there is a current flow of at
least 0.2 amperes.
---------------------------------------------------------------------------

    Toyota also requests that NHTSA amend S6.4 of FMVSS No 305 which
requires vehicles to satisfy all of the post-crash performance
requirements ``after being rotated on its longitudinal axis to each
successive increment of 90 degrees . . . . .'' to indicate that
compliance with electrical isolation and physical barrier protection
requirements would be evaluated after the vehicle is rotated a full 360
degrees. Toyota notes that the vehicle conditions related to the
electrical isolation and physical barrier protection requirements do
not change at various increments of a rollover and that it would be
unreasonably dangerous for laboratory personnel to conduct the
specified tests with the vehicle at 90 degree increments.

VI. Alliance Petition for Rulemaking

    On November 10, 2014, the Alliance submitted a petition for
rulemaking to update and upgrade FMVSS No. 305 to incorporate a
physical barrier compliance option to provide protection against
electric shock. The Alliance states that the implementation of a
physical barrier compliance option is especially critical to facilitate
both the introduction of complying HFCVs as well as 48 volt mild hybrid
technologies.\42\ The petitioner also believes the amendments would
enable safe design innovation for all electrified vehicles, as well as
reduce CO2 emissions and increase fuel economy.
---------------------------------------------------------------------------

    \42\ 48 volt mild hybrid systems are generally internal
combustion engines and a 48 volt battery equipped with an electric
machine (one motor/generator in a parallel configuration) allowing
the engine to be turned off whenever the car is coasting, braking,
or stopped, yet restart quickly. These mild hybrids may employ
regenerative braking and some level of power assist to the internal
combustion engine, but do not have an exclusive electric-only mode
of propulsion.
---------------------------------------------------------------------------

    The Alliance states that the physical barrier compliance option is
essential for FMVSS No. 305 certification of HFCVs in low speed crashes
where the automatic disconnect is not designed to operate. The Alliance
also states that in such crashes, the DC high voltage source can
impinge on the AC high voltage sources through the inverter, making it
impractical to achieve 500 ohms/volt electrical isolation for the AC
high voltage source.
    The Alliance explains that while it would seem that 48 volt mild
hybrid systems would not be within the intended scope of FMVSS No.
305,\43\ these systems typically convert DC voltage into three-phase AC
voltage that can exceed the 30 VAC voltage threshold for consideration
as a high voltage source in FMVSS No. 305.\44\ The

Alliance states that these 48 volt mild hybrid systems are grounded to
the vehicle chassis and so cannot viably meet the existing isolation
resistance option as well as the pretest measurement for isolation
resistance. The Alliance notes that while it is feasible to design a 48
volt mild hybrid system that meets FMVSS No. 305 electrical isolation
requirements, isolated systems inherently involve more complexity,
higher consumer costs, and higher mass resulting in reduced fuel
economy and increased emissions. The Alliance suggests that these
results are particularly inappropriate since there is no incremental
safety benefit provided by an isolated system compared to physical
barriers. The Alliance states that as a result, it is requesting
modifications to FMVSS No. 305 to permit the introduction 48 volt mild
hybrid systems and HFCVs into the U.S.
---------------------------------------------------------------------------

    \43\ FMVSS No. 305 considers electrical sources operating at
voltages greater than or equal to 30 VAC or 60 VDC as high voltage
sources that are subject to FMVSS No. 305 electrical safety
requirements.
    \44\ We have also considered information provided by Mercedes-
Benz in a briefing to the agency on June 2, 2015. As explained by
Mercedes-Benz, the AC-DC inverter converts the DC current from the
48 V battery into AC for the 3-phase AC motor. Mercedes-Benz showed
that the voltage between the electrical chassis and each of the
phases of the AC electric motor is switched DC voltage (voltage
between 0 and 48 volts). Since that voltage is less than 60 volts,
it is considered low DC voltage under FMVSS No. 305. However,
Mercedes-Benz noted that the voltage between two phases of the AC
motor is AC, and may be slightly greater than 30 VAC under certain
circumstances, which can be considered a high voltage AC source
under the standard. Mercedez-Benz explained its view that physical
barrier protection around the AC motor, and around cables from the
inverter to the motor, would mitigate human contact with these AC
high voltage sources, and thereby mitigate the likelihood of
electric shock. Additionally, the presenter showed that electrical
protection barriers enclosing the AC high voltage sources could be
conductively connected to the chassis with resistance less than 0.1
ohms, and thereby provide electric shock protection from indirect
contact of the high voltage sources. See the memorandum in the
docket for this NPRM on Mercedes-Benz, Daimler AG, input on 48 V
mild hybrid systems.
---------------------------------------------------------------------------

    The Alliance notes that in NHTSA's July 29, 2011, response to
petitions for reconsideration of the 2010 final rule,\45\ NHTSA
deferred consideration of the physical barrier protection option
pending additional research. The Alliance states that the agency's
research on the physical barrier option \46\ showed that electric shock
from indirect contact in a crash could only be possible, if the
following conditions were met (see Case 4 described above and
illustrated in Figure 8):
---------------------------------------------------------------------------

    \45\ 76 FR 45436.
    \46\ ``Hydrogen Fuel Cell Vehicle--Electrical Protective Barrier
Option,'' DOT HS 812134, May 2015, is available at http://www.nhtsa.gov/Research/Crashworthiness/Alternative%20Energy%20Vehicle%20Systems%20Safety%20Research and in
the docket for this NPRM.
---------------------------------------------------------------------------

    (1) A loss of electrical isolation within the enclosure of a high
voltage source,
    (2) a loss of electrical isolation within a second (different) high
voltage source enclosure,
    (3) these two distinct losses in isolation (specified in (1) and
(2)) occur on opposite rails (positive and negative) of the high
voltage source,
    (4) the overcurrent devices do not automatically open the circuit
as a result of the simultaneous loss of isolation on the positive and
negative rails to ground (the Alliance states that the normal design
practice is for the overcurrent devices to automatically open under the
circumstances outlined in (3)),
    (5) a person has access to these two enclosures in the crashed
vehicle, and
    (6) a person touches these two enclosures simultaneously.
    The Alliance believes that the likelihood of each of the above 6
events occurring is remote and that the simultaneous occurrence of
these events in real world situations is even more remote and
exceedingly small. The Alliance believes that the other scenarios
identified in the Battelle final report as having potential safety
concerns similarly require multiple failures in the system to occur,
followed by what the petitioner believes to be unlikely human contacts
and a lack of fuses or other electrical safety protection.
Nevertheless, the Alliance states that, despite the extremely low
likelihood of a safety issue from any of the scenarios in the final
Battelle report, the updated version of SAE J1766 (January 2014) \47\
includes performance requirements that safeguard against all safety
critical scenarios identified in the Battelle report.
---------------------------------------------------------------------------

    \47\ SAE J1766, ``Recommended practice for electric, fuel cell,
and hybrid electric vehicle crash integrity testing,'' January 2014,
SAE International, http://www.sae.org.
---------------------------------------------------------------------------

    The Alliance expresses its support of the December 23, 2013
petition for rulemaking from Toyota to modify FMVSS No. 305 to
facilitate the sale of HFCVs in the U.S. (petition discussed infra) and
notes that the January 2014 version of SAE J1766 also includes
provisions for a modified isolation requirement for AC systems with
physical barriers, as Toyota requests in its petition for rulemaking.
The Alliance states that SAE J1766 January 2014 also has provisions for
a ``stand-alone'' physical barrier protection compliance option that is
needed for facilitating the development of 48 volt mild hybrid systems,
since electrical components of these systems are conductively connected
to the chassis and so cannot viably satisfy electrical isolation
requirements. The Alliance believes that this ``stand-alone'' physical
barrier compliance option provides sufficient protection to address
potential (although unlikely, states the petitioner) safety critical
scenarios identified in the Battelle report.
    The Alliance asserts that while FMVSS No. 305 only evaluates
electrical safety in post-crash condition, auto manufacturers also
design for high voltage safety under normal operating conditions. The
petitioner states that providing physical barriers is the most common
method of protection against high voltage contact in the automotive
industry, as well as other industries that use high voltage electric
circuits. The Alliance believes it is reasonable that this method of
protection against electric shock hazard can also be used for post-
crash shock protection provided these physical barriers remain intact
post-crash, and that either the voltage between exposed conductive
parts is below 30 VAC or 60 VDC, or resistance between exposed
conductive parts of the barriers and electrical chassis is below
specified resistance levels.
    The Alliance states it is urgent to update FMVSS No. 305 to
facilitate the introduction of HFCVs and 48 volt mild hybrid technology
vehicles that are necessary to accommodate compliance with Corporate
Average Fuel Economy (CAFE) standards. Consequentially, the petitioner
states that it is not additionally requesting adoption of the low
energy compliance option that is also included in SAE J1766 January
2014. Instead the petitioner requests that the low energy compliance
option be considered for the electric vehicle safety (EVS) GTR that is
currently in process.
    SAE J1766 January 2014 also changes the time criterion for
initiating verification of post-crash electrical safety from 5 seconds
after the vehicle comes to rest (similar to the specification currently
in FMVSS No. 305) to 10 seconds after initial impact. The Alliance
states that given the urgency necessary to facilitate the introduction
of HFCVs and 48 volt mild hybrid technology, it is limiting its
petition for rulemaking to only include the post-crash physical barrier
protection compliance option in SAE J1766 January 2014 into FMVSS No.
305.
    Specifically, the Alliance requests including section 5.3.4 of SAE
J1766 January 2014 into FMVSS No. 305. This section provides two
options for post-crash electrical safety by means of physical barriers.
    The first option (Option 1 for physical barrier protection) is
similar to the post-crash physical barrier protection option for
electrical safety in GTR No. 13,\48\ but includes an additional
requirement that the resistance between the high voltage source
enclosed by the physical barrier and the exposed conductive parts of
the electrical protection barrier be greater than 0.01 ohms/volt for DC
high voltage sources and 0.05 ohms/volt for AC high voltage sources.
---------------------------------------------------------------------------

    \48\ Protection against direct contact with high voltage sources
is provided by protection degree IPXXB and protection against
indirect contact of high voltage sources is provided by requiring
the resistance between exposed conductive parts and the electrical
chassis to be lower than 0.1 ohm when there is a current flow of at
least 0.2 amperes.
---------------------------------------------------------------------------

    The second option for electrical safety through electrical
protection barriers (Option 2 for physical barrier protection) in SAE
J1776 January 2014

is through protection from direct contact by protection degree IPXXB,
and that the voltage between the electrical protection barrier and
other exposed conductive parts and the electrical chassis is less than
or equal to 30 VAC for AC high voltage sources and 60 VDC for DC high
voltage sources. The Alliance states that Option 2 is similar to the
low voltage option already in FMVSS No. 305.
    The Alliance supplemented its petition by a submission dated
October 20, 2015, which provided an analysis of its proposal for
electrical safety through physical barriers.\49\ Figure 9, below,
presents the circuit diagram the petitioner provided for the
representation of a high voltage source (e.g., battery) with voltage of
1,000 VAC or 1,500 VDC, enclosed in physical barriers that are
conductively connected to the electrical chassis with resistance less
than or equal to 0.1 ohms. The circuit diagram also has a
representation of a human body with a minimum resistance of 500 ohms
\50\ contacting protective barriers enclosing opposite rails of the
high voltage source. The resistances R1 and R2 in
Figure 9 represent the resistance between the high voltage source and
the protective physical barriers that enclose it. This circuit diagram
is a representation of the indirect contact Battelle scenario, Case 4,
in the event that electrical isolation of the high voltage source to
the chassis is lost and RiH and RiL are equal to
zero.
---------------------------------------------------------------------------

    \49\ The Alliance analysis of the physical barrier protection
option proposed for electrical safety (October 2014) is in the
docket of this NPRM.
    \50\ According to IEC TC-60479-I, ``Effects of current on human
beings and livestock--Part I--General Aspects,'' 2005, the lowest
possible electrical resistance of a human body is 500 ohms.
[GRAPHIC] [TIFF OMITTED] TP10MR16.008

    According to Option 1 of the electrical protection barrier in the
Alliance submission, the combined resistance \51\ of R1 and R2 is
required to be less than or equal to 0.05 ohms/VAC or 0.01 ohms/VDC.
Under Option 2, the voltage difference between barrier #1 and barrier
#2 is required to be less than or equal to 30 VAC or 60 VDC. The
Alliance observes that its analysis using the model in Figure 9
demonstrates that the proposed physical barrier protection option
provides equivalent levels of safety as the electrical isolation option
\52\ currently in FMVSS No. 305 in all the safety critical scenarios
identified in the Battelle study, including the scenario Case 4 for
indirect contact.
---------------------------------------------------------------------------

    \51\ R1 and R2 resistances are in a parallel configuration.
    \52\ The current through the body Ib (shown in Figure 9) is less
than or equal to 10 mA of direct current or 2 mA of alternating
current.
---------------------------------------------------------------------------

    The Alliance also states that the Option 1 electrical protection
barrier is the same as that of Option 2 since the conditions that meet
the Option 1 requirements also meet the Option 2 requirements. The
Alliance acknowledges that it is difficult to measure the resistance
between a high voltage source and the exposed conductive parts of the
electrical protection barrier that encloses the high voltage source, as
is needed to evaluate the Option 1 electrical protection barrier.\53\
The Alliance recommends that NHTSA incorporate Option 2 (direct contact
protection degree IPXXB and voltage between electrical protection
barrier and exposed conductive parts less than or equal to 30 VAC or 60
VDC) into FMVSS No. 305 since its analysis indicates that compliance
with Option 1 would also entail compliance with Option 2.
---------------------------------------------------------------------------

    \53\ The resistance level is too low to measure accurately and
in order to access a high voltage source enclosed in the physical
barrier, some disassembly of the barrier may be required in some
cases.
---------------------------------------------------------------------------

    The Alliance specifies the following test procedures from Appendix
C in SAE J1766 January 2014: (1) Section C.1 for verifying IPXXB
protection degree of physical barriers, which is similar to the
procedure in GTR No. 13, (2) Section C.2.1 for verifying that the
resistance between electrical protection barriers and electrical
chassis is less than 0.1

ohms, and (3) Section C.2.3 to verify that the voltage difference
between any two exposed conductive parts of the electric chassis
(including physical barriers) is less than or equal to 30 VAC or 60
VDC. The Alliance also specifies Section C.2.2 in SAE J1766 January
2014 for verifying that the resistance between a high voltage source
and the electrical chassis \54\ is greater than or equal to 0.05 ohms/
VAC or 0.01 ohms/VDC. We note, however, that section C.2.2 does not
provide a specific method of measurement and instead states, ``The
measurement may be performed by any means that provides sufficient
accuracy for the post-crash situation.''
---------------------------------------------------------------------------

    \54\ Since the resistance between a protective physical barrier
and the electrical chassis is required to be less than or equal to
0.1 ohm (a very low value), the resistance between a high voltage
source and the physical barrier would be the same as or only
slightly lower than the resistance between the high voltage source
and the electrical chassis.
---------------------------------------------------------------------------

    These test procedures are further discussed in a later section
analyzing the petitions for rulemaking to modify FMVSS No. 305.

VII. Overview of Proposed Rule

    NHTSA is initiating rulemaking to consider adopting GTR No. 13 into
FMVSS No. 305, as appropriate under the Vehicle Safety Act, and to
address the issues raised by the Alliance and Toyota in their
respective petitions. We request comment on the decisions put forth in
this NPRM, including those regarding minor additional provisions that
the agency is considering to address the concerns of the petitioners.
    NHTSA believes that this NPRM would improve the level of safety
afforded to the public. Adopting the provisions from GTR No. 13 that
reduce the risk of harmful electric shock during normal vehicle
operation would improve FMVSS No. 305 by expanding its performance
requirements beyond post-crash conditions. The proposed requirements
would provide post-crash compliance options for new power train
configurations that ensure that those configurations provide a
comparable level of post-crash safety compared to existing electric
vehicles.
    The proposed amendments are summarized as follows. In furtherance
of implementing GTR No. 13 and in response to the petitions for
rulemaking--
    a. This NPRM proposes to add electrical safety requirements for
vehicle performance during normal vehicle operations (as opposed to
during and after a crash), to mitigate electric shock due to loss in
electrical isolation and direct or indirect contact of high voltage
sources. The electrical safety requirements during normal vehicle
operations would include requirements for:

1. Direct Contact Protection From High Voltage Sources

    i. IPXXD protection level for high voltage sources inside
passenger and luggage compartments. IPXXB protection level for high
voltage sources not in passenger and luggage compartments.
    ii. IPXXB protection level for service disconnect that can be
opened or removed without tools.
    iii. Markings on barriers of high voltage sources that can be
physically accessed, opened, or removed without the use of tools.
    iv. Orange color outer covering for cables of high voltage
sources that are located outside electrical protection barriers.

2. Indirect Contact Protection From High Voltage Sources

    Exposed conductive parts of electrical protection barriers would
have to be conductively connected to the chassis with a resistance
less than 0.1 ohms, and the resistance between two simultaneously
reachable exposed conductive parts of electrical protection barriers
that are within 2.5 meters of each other would have to be less than
0.2 ohms.

3. Electrical Isolation of High Voltage Sources

    i. 500 ohms/volt or higher electrical isolation for AC high
voltage sources and 100 ohms/volt or higher for DC high voltage
sources
    ii. For conditions where AC and DC bus are connected, AC high
voltage sources would be permitted to have electrical isolation of
100 ohms/volt or higher, provided they also have the direct and
indirect contact protection described in 1 and 2, above.
    iii. There would be an exclusion of 48 volt hybrid vehicles from
electrical isolation requirements during normal vehicle operation.

4. Electrical Isolation Monitoring System for DC High Voltage Sources
on Fuel Cell Vehicles

5. Electrical Safety During Charging Involving Connecting the Vehicle
to an External Electric Power Supply

    i. Minimum electrical isolation resistance of one million ohms
of the coupling system for charging the electrical energy storage
system; and
    ii. Conductive connection of the electric chassis to earth
ground before and during exterior voltage is applied.

6. Mitigating Driver Error by--

    i. Requiring an indication to the driver when the vehicle is in
active driving mode upon vehicle start up and when the driver is
leaving the vehicle; and,
    ii. Preventing vehicle movement by its own propulsion system
when the vehicle charging system is connected to the external
electric power supply.
    b. This NPRM proposes to amend FMVSS No. 305's post-crash
electrical safety requirements. The post-crash electrical safety
requirements would include:

    1. Adding an additional optional method of meeting post-crash
electrical safety requirements through physical barrier protection
from high voltage sources. The proposed specifications of this
optional method of electric safety include requirements ensuring
that:
    i. High voltage sources would be enclosed in barriers that
prevent direct human contact with high voltage sources (IPXXB
protection level),
    ii. Exposed conductive parts of electrical protection barriers
would be conductively connected to the chassis with a resistance
less than 0.1 ohms, and the resistance between two simultaneously
reachable exposed conductive parts of electrical protection barriers
that are less than 2.5 meters from each other would be less than 0.2
ohms, and
    iii. Voltage between a barrier and other exposed conductive
parts of the vehicle would be at a low voltage level that would not
cause electric shock (less than 60 VDC or 30 VAC).
    2. Permitting an AC high voltage source that is conductively
connected to a DC high voltage source to meet lower minimum
electrical isolation requirement of 100 ohms/volt provided the AC
high voltage source also has physical barrier protection specified
in 1, above.

VIII. Proposal Addressing Safety During Normal Vehicle Operations

    We first discuss the proposed requirements for vehicle performance
during normal vehicle operations, followed by those for performance
post-crash.

a. Direct Contact Protection From High Voltage Sources

    GTR No. 13 specifies safety measures to ensure that high voltage
sources cannot be contacted. This safety measure is to enclose high
voltage sources in physical barriers (electrical protection barriers)
to prevent direct human contact. NHTSA is proposing to include in FMVSS
No. 305 the direct contact protection requirements specified in GTR No.
13 for the passenger and luggage compartments and other areas.\55\
---------------------------------------------------------------------------

    \55\ GTR No. 13 assesses the potential for direct contact with
high voltage components using test probes specified in ISO 20653.
---------------------------------------------------------------------------

    NHTSA is proposing to assess protection against direct contact with
high voltage sources contained inside the passenger and luggage
compartments using a 1.0 mm diameter and 100 mm long test wire probe
(IPXXD). This test probe ensures that any gaps in the protective
barriers are

no larger than 1 mm and that any live components contained within are
no closer to the gap than 100 mm. This ensures that body parts,
miscellaneous tools or other slender conductive items typically present
in a passenger or luggage compartment cannot penetrate any gaps/seams
in the protective enclosures and contact high voltage components
contained within.
    For assessing protection against direct contact with high voltage
sources in areas other than the passenger and luggage compartments
under normal operating conditions, NHTSA is proposing to use the test
probe IPXXB, representing a test finger. In areas other than the
passenger and luggage compartments, the barrier would not likely
contact tools and other slender conductive items. Therefore, protection
using the test wire probe IPXXD would not be necessary and the test
finger probe IPXXB would be appropriate to prevent inadvertent contact
with high voltage components contained in the protective enclosures, by
persons such as mechanics.
    GTR No 13 also requires that a service disconnect that can be
opened, disassembled, or removed without tools requires IPXXB
protection when it is opened, disassembled, or removed. NHTSA is
proposing to include this requirement into FMVSS No. 305, as well as a
definition for a service disconnect.
    NHTSA is proposing marking (yellow high voltage symbol) for
enclosures and barriers of high voltage sources that can be physically
accessed, opened, or removed without the use of tools, similar to GTR
No. 13. As explained earlier in this preamble, we are not excluding
some barriers as GTR No. 13 does.
    NHTSA is proposing that cables for high voltage sources which are
not located within electrical protection barriers to be identified by
an orange color outer covering, similar to GTR No. 13. However, as
explained earlier in this preamble, we are not excluding some
connectors as GTR No. 13 does.
    As noted earlier in this preamble, GTR No. 13 specifies direct
contact protection requirements for high voltage connectors separately,
and has exclusions with which we do not agree. Per GTR No. 13,
connectors do not need to meet IPXXB protection if they are located
underneath the vehicle floor and are provided with a locking mechanism,
or require the use of tools to separate the connector, or the voltage
reduces to below 30 VAC or 60 VDC within one second after the connector
is separated. For the reasons given earlier, NHTSA does not believe
that the exclusions are warranted and does not anticipate adopting them
in a final rule.

b. Indirect Contact Protection From High Voltage Sources

    Under GTR No. 13, exposed conductive parts (parts that can be
contacted with the test probes, IPXXD or IPXXB, and become electrically
energized under electrical isolation failure conditions) have to be
protected against indirect contact during normal vehicle operation. GTR
No. 13 requires electrical protection barriers or enclosures of high
voltage sources to be conductively connected to the electrical chassis
with resistance of no more than 0.1 ohms during normal vehicle
operations. This requirement would provide protection from electric
shock by shunting \56\ any harmful electrical currents to the vehicle
chassis should any electrically charged components lose isolation
within the protective barrier.
---------------------------------------------------------------------------

    \56\ Shunting is when a low-resistance connection between two
points in an electric circuit forms an alternative path for a
portion of the current. If a human body contacts an electrical
protection barrier that is energized due to loss in electrical
isolation of a high voltage source enclosed in the barrier, most of
the current would flow through the chassis rather than through the
human body because the current path through the chassis has
significantly lower resistance (less than 0.1 ohm) than the
resistance of the human body (greater or equal to 500 ohm).
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    For indirect contact protection, we propose to apply the same
indirect contact protection requirements and test procedures as would
apply under post-crash conditions (see discussion in next section,
below). The proposed indirect contact protection requirements would be
for exposed conductive parts of electrical protection barriers to be
conductively connected to the chassis with a resistance less than 0.1
ohms and that the resistance between two simultaneously reachable
exposed conductive parts of electrical protection barriers that are
within 2.5 meters of each other be less than 0.2 ohms. These
resistances would be measured by passing a current of at least 0.2 A
between exposed conductive parts and the electrical chassis. For the
reasons previously discussed, NHTSA is not including GTR No. 13's
provision that permits visual inspection of welds as a method of
assessing compliance of indirect contact protection.

c. Electrical Isolation of High Voltage Sources

    This NPRM would require that under normal operating conditions, all
high voltage sources of the power train and those connected to the
power train have sufficient electrical isolation resistance measured
against the electrical chassis to ensure that current flowing through a
human body in contact with the vehicle is not dangerous.
    For conditions where DC and AC high voltage sources are isolated
from each other, DC high voltage sources would be required to have a
minimum electrical isolation of 100 ohms/volt and AC high voltage
sources would be required to have a minimum of 500 ohms/volt.
    For conditions where DC and AC high voltage sources are connected,
AC and DC high voltage sources would be permitted to have a minimum
electrical isolation of 100 ohms/volt, provided the AC high voltage
source has direct and indirect contact protection in a. and b. above.
    We proposed to exclude 48 volt hybrid vehicles from these
electrical isolation requirements during normal vehicle operation.
Since electric components in 48 volt mild hybrid systems are
conductively connected to the electric chassis, these systems would not
be able to comply with electrical isolation requirements both during
normal vehicle operations and after a crash. Therefore, we believe that
the ``normal use'' requirements in GTR No. 13 need to be modified to
permit the introduction of 48 volt mild hybrid systems.
    The United Nations Economic Commission for Europe Regulation 100
(ECE R.100) \57\ normal operation requirements were modified on June
10, 2014 to facilitate the development and sale of 48 volt mild hybrid
systems. Under these changes, 48 volt mild hybrid systems that are
conductively connected to the electrical chassis are exempt from the
in-use electrical isolation requirements. However, electrical
protection barriers are still required during normal vehicle operations
for high voltage components of these 48 volt mild hybrid systems so as
to provide direct and indirect contact protection. As discussed in a
later section for post-crash electrical safety requirements, we believe
that these 48 volt mild hybrid systems with electrical protection
barriers for all high voltage components in the system would not pose
concerns regarding electric shock. Therefore, NHTSA proposes to include
a similar exclusion from in-use electrical isolation requirements for
48 volt mild hybrid systems that are conductively connected to the
electrical chassis.
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    \57\ Uniform Provisions Concerning the Approval of Vehicles with
Regard to Specific Requirements for the Electric Power Train, ECE
R.100-02, June 24, 2014.

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d. Electrical Isolation Monitoring System for DC High Voltage Sources
on Fuel Cell Vehicles

    GTR No. 13 requires that DC high voltage sources (other than the
coupling system for charging) in HFCVs have an on-board electrical
isolation monitoring system, together with a warning to the driver if
the isolation resistance drops below the minimum required value of 100
ohms/volt. Similarly, FMVSS No. 305 currently specifies that DC high
voltage sources that comply with electrical safety requirements by the
electrical isolation of 100 ohms/volt must have an electrical isolation
monitoring system to warn the driver. SiCnce most HFCVs would comply
with the electrical isolation requirements in FMVSS No. 305 using the
100 ohms/volt option,\58\ these HFCVs, which must have an electrical
isolation monitoring system under GTR No. 13, would also be required by
FMVSS No. 305 to have the monitoring system.
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    \58\ In fuel cell vehicles, the presence of fuel cell coolant
may not permit electrical isolation levels of 500 ohms/volt of the
DC source.
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    Nonetheless, to ensure that the intent of GTR No. 13 and FMVSS No.
305 are met, the agency is proposing to amend FMVSS No. 305 to indicate
expressly that each DC high voltage source in fuel cell vehicles would
need to be equipped with an electrical isolation monitoring system.

e. Protection From Electric Shock During Charging

    GTR No. 13 requires electric vehicles whose rechargeable energy
storage system are charged by conductively connecting to an external
power supply to have a device to enable conductive connection of the
electrical chassis to the earth ground during charging. Additionally,
GTR No. 13 requires the isolation resistance between the high voltage
source and the electrical chassis to be at least 1 million ohms when
the charge coupler is disconnected. The first requirement ensures that
in the event of electrical isolation loss during charging, a person
contacting the vehicle does not form a ground loop with the chassis and
sustain significant electric shock. The second requirement ensures that
the magnitude of current through a human body when a person contacts a
vehicle undergoing charging is low and in the safe zone. NHTSA believes
these two normal use charging safety requirements are warranted and
proposes to include them in FMVSS No. 305.

f. Mitigating Driver Error

    Consistent with GTR No. 13, we propose amending FMVSS No. 305 to
add requirements that mitigate the likelihood of driver error in
operating electric vehicles. First, we propose requiring vehicles to
provide an indication to the driver when the vehicle is in an active
driving mode upon vehicle start up and when the driver is leaving the
vehicle.\59\ Second, we propose requiring vehicles to prevent vehicle
movement by its own propulsion system when the vehicle charging system
is connected to the external electric power supply.
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    \59\ We note that an NPRM issued on FMVSS No. 114, ``Theft
protection and rollaway prevention'' (76 FR 77183) proposes to
require vehicles with keyless ignition controls to provide an
audible warning to the driver exiting the vehicle while the
propulsion system is operating. We request comment on whether the
FMVSS No. 114 requirement, if adopted, would satisfy this provision
in the GTR.
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IX. Proposal Addressing Safety Post-Crash

    FMVSS No. 305 requires that after a crash, each high voltage source
in the vehicle are either electrically isolated from the vehicle's
chassis, or their voltage is reduced to levels considered safe from
electric shock hazards (i.e., less than 30 VAC or less than 60 VDC).
    As noted in earlier sections, GTR No. 13 specifies that vehicles
may meet regulatory requirements by having no high voltage levels (see
(a) below), meet physical barrier protection requirements (see (b))
below, or meet electrical isolation requirements (see (c) below):

    a. Voltage levels: The voltages of the high voltage source must
be less than or equal to 30 VAC or 60 VDC within 60 seconds after
the impact. (This option for electrical safety is currently in FMVSS
No. 305.)
    b. Electrical protection barrier: The physical protection
requirement is an option each contracting party of the 1998
agreement may elect to adopt. The provision is similar to the
electrical safety requirements during normal operations except that
the protection degree IPXXB applies rather than IPXXD. (The
provision for electrical protection through physical barriers is
currently not in FMVSS No. 305.)
    i. Protection from direct contact: Protection from direct
contact of high voltage sources with protection degree IPXXB
required.
    ii. Protection from indirect contact: The resistance between all
exposed conductive parts and electrical chassis is required to be
less than 0.1 ohms when there is a current flow of at least 0.2
A.\60\
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    \60\ GTR No. 13 considers this requirement to be met if visual
inspection indicates that conductive connection has been established
by welding. The minimum resistance requirement is only evaluated in
case of doubt.
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    c. Electrical isolation:
    i. If the AC and DC high voltage sources are conductively
isolated from each other, then the minimum electrical isolation of a
high voltage source to the chassis is 500 ohms/volt for AC
components and 100 ohms/volt for DC components of the working
voltage.
    ii. If AC and DC high voltage sources are conductively
connected, the minimum electrical isolation of AC and DC high
voltage sources must be--
     500 ohms/volt of the working voltage, or
     100 ohms/volt of the working voltage with the AC high
voltage sources meeting the physical protection requirements in (b)
or have no high voltage as specified in (a).

    (FMVSS No. 305 does not distinguish AC and DC high voltage sources
that are conductively connected from those that are isolated. Thus, the
method above for complying with electrical isolation requirements when
AC and DC high voltage sources are connected post-crash (see c. ii.
above) is not now available in FMVSS No. 305.)

Proposal

    This NPRM proposes to amend the isolation resistance compliance
option in FMVSS No. 305 to harmonize with GTR No. 13. We are proposing
to add an optional method of meeting post-crash electrical isolation
requirements for an AC high voltage source that is connected to a DC
high voltage source. In such condition, the required minimum electrical
isolation for the AC high voltage source is 100 ohms/volt provided the
AC high voltage source meets the post-crash physical barrier protection
requirements.
    We are also proposing to add a physical barrier protection option
for post-crash electrical safety that includes requirements specifying
that:

    i. High voltage sources must be enclosed in barriers that
prevent direct human contact with high voltage sources (IPXXB
protection level),
    ii. Electrical protection barriers must be conductively
connected to the chassis with a resistance less than 0.1 ohms, and
the resistance between two simultaneously reachable exposed
conductive parts of electrical protection barriers that are less
than 2.5 meters of each other must be less than 0.2 ohms, and
    iii. Voltage between a barrier and other exposed conductive
parts of the vehicle must be at a low voltage level that would not
cause electric shock (less than 60 VDC or 30 VAC).

Electrical Isolation Resistance Option

    Currently, FMVSS No. 305's electrical isolation option requires
that vehicles with high voltage sources meet different isolation
requirements based on whether the vehicle is an AC or a DC high voltage
source. Electric powered vehicles are required to electrically isolate
AC and DC high voltage sources from the chassis with electrical
isolation no less than 500 ohms/volt, but the DC high voltage source
can have electrical isolation no less than 100 ohms/volt if

the DC high voltage source has an electrical isolation monitoring
system.
    GTR No. 13 differs from FMVSS No. 305 by distinguishing between
situations where AC and DC high voltage are conductively isolated from
each other or are conductively connected. GTR No. 13 states that when
AC and DC high voltage sources are isolated from each other, the AC
high voltage sources need to maintain electrical isolation no less than
500 ohms/volt and DC sources need to maintain electrical isolation no
less than 100 ohms/volt. This is similar to FMVSS No. 305.\61\
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    \61\ We note that GTR No. 13 permits DC high voltage sources to
have 100 ohms/volt minimum electrical isolation without specifying
that the DC high voltage sources must be equipped with an electrical
isolation monitoring system. While this appears to differ from FMVSS
No. 305, we do not believe there is a practical difference. The only
vehicles needing to use FMVSS No. 305's 100 ohms/volt electrical
isolation compliance option for DC high voltage sources are fuel
cell vehicles. In this NPRM, the agency is proposing to require all
DC high voltage sources of fuel cell vehicles to be equipped with an
electrical isolation monitoring system. Therefore, while we propose
to adopt the post-crash electrical isolation requirements for DC
high voltage sources in GTR No. 13 into FMVSS No. 305 to further
harmonization efforts, we do not believe there would be an effect on
vehicle design or safety.
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    When the AC and DC sources are conductively connected, GTR No. 13
affords three different methods for these high voltage sources to
achieve compliance:
    (1) All AC and DC sources maintain minimum electrical isolation of
500 ohms/volt (this is basically the approach of FMVSS No. 305);
    (2) AC high voltage sources that are linked to a DC high voltage
source may have a minimum of 100 ohms/volt instead of 500 ohms/volt if
the AC high voltage source also has physical barrier protection from
direct and indirect contact of high voltage sources; \62\ or
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    \62\ FMVSS No. 305 does not distinguish when the AC and DC
sources are connected from when AC and DC sources are separated. The
standard specifies that all AC high voltage sources must have a
minimum electrical isolation of 500 ohms/volt. The condition
involving connected AC and DC high voltage sources is germane to the
Toyota petition.
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    (3) all AC and DC sources maintain a minimum isolation resistance
of 100 ohms/volt and all AC sources meet low-voltage requirements in
GTR No. 13.

Need for Amendment

    After reviewing the Toyota petition and other information, NHTSA
understands petitioners' concern about FMVSS No. 305's electrical
isolation requirements for AC high voltage sources under the conditions
when the AC and DC bus are conductively connected. We tentatively
believe that an amendment is warranted to facilitate the manufacture of
fuel cell and other vehicles.
    If FMVSS No. 305 were not amended, the electrical isolation for
fuel cell stacks would need to be 500 ohms/volt or greater to comply
with FMVSS No. 305, which may not be technically feasible.

Proposal for Electrical Isolation Option

    In consideration of the above, NHTSA is proposing to add an option
that would permit an AC high voltage source that is connected to a DC
high voltage source post-crash to have electrical isolation no less
than 100 ohms/volt provided the high voltage source also meets physical
barrier protection requirements. Specifically, the electrical isolation
option for electrical safety in the proposal requires that the
electrical isolation of a high voltage source be greater than or equal
to one of the following:
    (1) 500 ohms/volt for an AC high voltage source; or
    (2) 100 ohms/volt for an AC high voltage source if it is
conductively connected to a DC high voltage source, but only if the AC
high voltage source meets the physical barrier protection requirements;
or
    (3) 100 ohms/volt for a DC high voltage source.
    NHTSA tentatively believes that adding this option into the
existing FMVSS No. 305 requirements essentially harmonizes with the
electrical isolation option in GTR No. 13. When an AC and DC high
voltage source are conductively connected, the electrical isolation
measured will be the same for both high voltage sources and
approximately equal to the lower electrical isolation measurement of
the two. Accordingly, the combined electrical isolation of conductively
connected AC and DC high voltage sources can be greater than or equal