NHTSA received comments to the NPRM from seven vehicle manufacturers (Subaru, DaimlerChrysler, Porsche, Volkswagen, Ford, Honda, and General Motors), two vehicle manufacturer associations (Alliance of Automobile Manufacturers  and National Truck Equipment Association), three engineering firms (American Automotive Design, Dynamic Safety, and Syson-Hille and Associates), a test laboratory (Transportation Research Center), the Insurance Institute for Highway Safety, and a consumer advocate group, Advocates for Highway and Auto Safety. Their comments are summarized below by issue.
A. Rear Impact Test Procedure Upgrade
None of the commenters opposed the proposed rear impact test procedure upgrade.
The Alliance suggested that significant vehicle redesign will likely be required to meet the high speed rear crash requirements. Volkswagen (VW) stated that the rear end structure of small cars will need to be made stiffer, which could result in increased acceleration imposed on occupants in more common lower speed rear crashes. Honda commented that increased vehicle body and fuel tank deformation would occur, even on vehicles that pass the fuel leak requirements.
DaimlerChrysler (DC) stated its belief "that the proposal is likely to require significant changes to vehicle structure and design, which are yet to be fully defined and realized." DC argued that the proposed upgrade is a "major rulemaking effort which will present many challenges to the industry that may not yet be fully identified."
DC also expressed concerns with using a MDB at the proposed impact speed (80 km/h). DC stated that in impacts between a MDB and a vehicle at 80 km/h, DC has observed complete crushing of the barrier face and ensuing contact with the rigid cart backer plate and contact between the cart uprights and the impacted vehicle. DC recommended that NHTSA reevaluate the proposed test procedure upgrade to determine if the anticipated benefits could be achieved with a lower impact speed (such as 56-64 km/h), or provide design changes to the MDB and cart system.
GM and Ford observed bottoming of the barrier face to the backing plate and contact between the barrier uprights and the vehicle in some rear impact crash tests. GM also stated that the barrier face can underride the struck vehicle and, upon rebound, the upright that contacted the vehicle can become "caught" on vehicle structure (e.g., bumper, frame cross member, etc.), with undetermined effects on the struck vehicle. GM and Ford suggested that some changes to the MDB might be necessary. Ford recommended that the agency investigate "rounding the corners of the deformable portion of the barrier and increasing its depth." Ford stated that its testing indicated that the right angle corners of the barrier face can "hang up on trim," potentially affecting test repeatability.
Honda commented that it had conducted rear impact crash tests in accordance with the proposed test procedure. Honda noted that the MDB sometimes over-rode the rear of the test vehicle, and that in these instances, the rear frame structure of the vehicle could not absorb crash energy sufficiently to meet the fuel leaking requirements of Standard No. 301. Honda also noted, "Even in instances when the rear frame functioned somewhat to absorb energy, the increased speed and the off-set impact caused extensive deformation of the fuel tank." Honda stated that a vehicle in compliance with the proposed upgrade would have to absorb twice as much energy as a vehicle in compliance with Standard No. 301 as currently written. Honda argued that under the proposed upgrade, significant changes would have to be made to each of its vehicle models.
VW noted that the proposed rear impact would be to either side of the vehicle. VW recommended that this be changed so that the impact is on the side of the vehicle where the fuel filler pipe or filler neck is located. VW argued that impacting the side of the vehicle where the fuel filler pipe or filler neck is located would represent the worst case condition and establish a more objective requirement for enforcement purposes.
VW also commented that in order to assure compliance with the higher speed rear impact test, the vehicle rear end structure would have to be made stiffer, particularly in smaller cars. VW stated that this would tend to increase the potential for whiplash type injuries in lower speed crashes. VW recommended that NHTSA address this issue before issuing a final rule.
Ford commented that it has conducted voluntary, in-house 80 km/h vehicle-to-vehicle rear impact crash tests to evaluate fuel system integrity since the mid-1980s. Ford supported the agency's proposed test upgrade, stating, "Ford believes this test can provide a robust evaluation of a fuel system's integrity."
Syson-Hille commented that other vehicle manufacturers, such as GM, began conducting 80 km/h vehicle-to-vehicle rear impact crash tests in the 1980s, and that Mercedes-Benz marketing materials note that its vehicles have been designed to provide fuel system integrity in offset rear impact crashes since the early 1980s.
The Insurance Institute for Highway Safety (IIHS), Advocates for Highway and Auto Safety (Advocates), and American Automotive Design (AAD), urged NHTSA to require the use of a 4,000-pound rigid barrier, instead of the 3,015-pound MDB. IIHS and Advocates urged this based on their view that the Standard No. 214 barrier does not reflect the characteristics of pickup trucks and sport utility vehicles (SUV) and thus may not reproduce the patterns or extent of deformation seen when those types of vehicles strike cars in the side or rear.
B. Side Impact Test Procedure Upgrade
None of the commenters opposed the proposed side impact test procedure upgrade.
DC recommended that, as in the proposed rear impact test procedure, the agency specify that the MDB be lowered 50 mm (2 inches) in the proposed side impact test procedure. DC stated that data indicate that pre-impact braking occurs in 54 percent of side impacts.
C. Door System Integrity
Vehicle manufacturers generally opposed adding a post-crash test door operability requirement to Standard No. 206. The Alliance and GM agreed with and supported the logic regarding a post-crash test door operability requirement. However, the Alliance and GM stated that Standard No. 206 addresses component level performance, while a post-crash test door operability requirement would address vehicle level performance. The Alliance stated that adding such a requirement to Standard No. 206 would necessitate the addition of vehicle crash test requirements to the standard as well. The Alliance also stated,
Prior to proposing such requirements in future rulemakings, NHTSA would need to develop and define an objective set of meaningful and measurable requirements pertaining to the applicability of doors (front rear, sliding, etc.), number of doors (per row, per vehicle, etc.), and methodology by which operability would be assessed (without the use of tools is an insufficient measure, as NHTSA has concluded in past rulemaking efforts).
GM stated that such a requirement would be more appropriate if it were added to crash tests that are already required for other safety standards, such as Standard No. 208, Occupant crash protection, Standard No. 214, Side impact protection, or Standard No. 301. GM noted that it currently performs door operability evaluations following most barrier tests.  GM argued that NHTSA should develop meaningful, appropriate, objective, and repeatable requirements for post-crash test door operability after further research and through separate rulemaking.
DC argued that NHTSA has not provided sufficient evidence to demonstrate the need for adding a post-crash test door operability requirement to Standard No. 206. DC recommended that NHTSA conduct research to determine such a requirement's real world benefits, feasibility, and effects on vehicle design, cost, and weight. DC suggested that if NHTSA persists in such a rulemaking, the agency require only one operable door per vehicle.
Advocates supported adding a post-crash test door operability requirement to Standard No. 206. Advocates stated:
Advocates believes that ensuring that doors can be opened after crashes is not a safety problem involving only fire-related collisions. It is a major safety issue long overdue for agency regulatory attention. Many thousands of crashes every year result in vehicle deformation preventing door opening. In these crashes, numerous people are seriously injured whose lives could be saved or the severity of their injuries substantially reduced if rescue squads could quickly reach them without recourse either to the use of Jaws of Life or to being forced to extricate a seriously injured person through a window or windshield, a common practice.
Syson-Hille also supported a post-crash test door operability requirement. Syson-Hille recommended that the agency require at least one door on two-door vehicles and three doors on four-door vehicles to be operable after a crash test.
D. Lead Time
The vehicle manufacturers all supported the three-year lead time proposed in the NPRM for the rear impact test upgrade, but recommended that the agency add a phase-in after that period. The Alliance recommended a four-year phase-in with an implementation schedule of 25 percent compliance the first year, 40 percent the second year, 70 percent the third year, and 100 percent the fourth year. The Alliance also recommended that the agency grant carry forward credits for early compliance.
The Alliance argued that a phase-in is necessary because the Alliance considered this to be a "major rulemaking, particularly in response to the substantially increased impact energy of the high speed rear offset impact testing proposed." The Alliance stated:
Significant vehicle redesign and retooling for production will likely be required in a number of vehicles. The small number of tests conducted by the NHTSA, often with a sample size of one vehicle, simply is inadequate to identify whether vehicle changes are required or for any manufacturer to assure compliance for all its vehicles.
DC supported the Alliance's recommended phase-in schedule. DC argued that such a phase-in would "allow the efficient phasing out of older models designed to the current requirements with replacements that are thoroughly designed, constructed and tested to meet the more stringent requirements without very costly and disruptive mid cycle manufacturing changes."
Subaru recommended a three-year full phase-in, with complete compliance after the third year. Honda suggested a four-year phase-in with an implementation schedule of 10 percent, 30 percent, 70 percent, and 100 percent. Porsche supported the Alliance's recommended lead time but requested that the agency provide small volume manufacturers the option of coming into compliance at the 100 percent level in the third year of the phase-in with no requirements in the first two years.
IIHS stated that the proposed three-year lead time for the rear impact test upgrade should be sufficient.
Vehicle manufacturers supported the one-year lead time proposed in the NPRM for the side impact test upgrade, but recommended that the agency add a phase-in after this lead time. The Alliance and Ford recommended a four-year phase-in with an implementation schedule of 25 percent compliance the first year, 40 percent the second year, 70 percent the third year, and 100 percent the fourth year. The Alliance also recommended that the agency grant carry forward credits for early compliance.
IIHS stated that the one-year lead time proposed by the agency in the NPRM should be sufficient.
E. Costs and Benefits
Honda commented that the agency's cost estimates were insufficient. Honda stated, "The cost of managing all the accompanying issues is at least 10 times greater than NHTSA's cost estimation." Honda claimed that to meet the proposed rear impact test upgrade, "It will be necessary to change the thickness of the vehicle's rear structure, which requires the modification of existing dies and manufacturing of new dies and parts."
VW questioned the safety benefits of the proposed test upgrades. VW stated:
The accident data base of the Medical University of Hanover in Germany indicates that in the universe of crashes with at least one injured occupant, only 0.58 percent resulted in after-crash fire and only 0.4 percent of the injuries in the data base were fire related. In the same sample of crashes, the whiplash injuries were reported in 11 percent of the cases. Although the vehicle fleet population in Germany is different from that in the U.S., Volkswagen submits that the statistics support the very low incidence of post-crash fires and fire related injuries.
F. Additional Issues
The agency asked in the NPRM whether there were any real-world data, other than the data that NHTSA had already analyzed, that may better describe the relationship between the risk of occupant injury due to fire and crash severity.
The Alliance, GM, DC, and Ford stated that there were no such data. The Alliance and GM commented that both the FARS and NASS files might need to be modified to more accurately define any remaining fire risk.
In the NPRM, the agency noted that in the various crash tests that were performed during the research for this rulemaking, the values of head and neck injury criteria measured by the two front seat dummies were much higher than acceptable thresholds. The agency asked what these high injury values indicate about the real world potential for trauma injury to vehicle occupants in rear impacts.
The Alliance stated that its members would need access to more details of NHTSA's test program in order to respond to this question.  However, the Alliance argued that the issue of occupant protection in rear impacts is outside the scope of this rulemaking. The Alliance recommended that the agency address this issue in the ongoing Standard No. 202, Head restraints, rulemaking or in a possible future upgrade of Standard No. 207, Seating systems. The Alliance also commented that more research is needed to provide an appropriate level of seating system performance dealing with the proposed rear impact test upgrade.
Syson-Hille commented that both GM and Mercedes-Benz have been using 50 mph vehicle-to-vehicle rear impact tests, with occupant survival space criteria, since the 1980s. Advocates suggested that the agency consider upgrading requirements for the entire seating system (seat, seat back, and head restraint) to provide improved occupant protection in the proposed Standard No. 301 rear impact test upgrade.
In the NPRM, the agency asked how seat back failures influence injury potential in rear impacts. The agency also asked for data that would aid it in determining the need for improving seat back strength and the appropriate requirements for doing so.
The Alliance stated that without a definition of "seat back failure" it could not answer the question. However, the Alliance defined the optimal seat back strength as the balance between strength and flexibility to address both severe and minor impacts.
DC and Ford supported the Alliance's comments. DC commented that the issue of seat back strength is outside the scope of this rulemaking, and should be addressed in a possible future upgrade of Standard No. 207. Ford stated that seat back strength should be designed to enhance occupant safety in real-world crashes.
GM agreed with an upgrade of Standard No. 207 seat back strength requirements in the future. However, GM stated that this should be done in a separate rulemaking.
VW commented that a single optimal level of seat back strength is extremely difficult to define because of the range in impact severity (a function of impact speed and the impacting vehicle structure in real-world crash situations).
Advocates thinks it would be difficult for the agency to justify instituting the proposed rear impact fuel integrity test without reforming Standard No. 207 to prevent seat back collapse while also ensuring much better head restraint protection against whiplash injuries. It is obvious that it is unacceptable to propose a new crash test in which the majority of seatbacks in the test vehicles collapse or occupants suffer severe whiplash injuries in seats which maintain their upright positions. … Advocates is concerned that, in the short term, manufacturers may simply increase seat back strength, especially rigidity, to prevent seat backs from collapsing in the new No. 301 rear impact test.
In the NPRM, the agency asked whether it should require vehicles to meet the requirements of Standard No. 301 in tests with 5th percentile female dummies as well as with the currently-required 50th percentile male dummies.
The Alliance, DC, GM, VW, and Ford opposed requiring the use of 5th percentile female dummies in Standard No. 301 rear impact tests. The Alliance stated that different dummy sizes would only change the total impact weight of the tested vehicles and would have little or no effect on the performance of the fuel system. However, GM supported the voluntary use of instrumented test dummies for research to understand better the mechanics and magnitude of the potential for injury for various dummy sizes in different crash situations.
Advocates supported requiring the use of 5th percentile female dummies in the proposed rear impact test procedure. Advocates stated this would help prevent occupant injury due to ramp up of the seat back. In addition, Advocates suggested that the agency require use of the 95th percentile male dummy in Standard No. 301 rear impact tests to help prevent occupant injury due to seat back failure.
In the NPRM, the agency proposed to eliminate the second sentence of S7.1.6(b) of Standard No. 301. That sentence reads:
If the weight on any axle, when the vehicle is loaded to unloaded vehicle weight plus dummy weight, exceeds the axle's proportional share of the test weight, the remaining weight shall be placed so that the weight on that axle remains the same.
The Alliance, Ford, and VW opposed the elimination of that sentence. The Alliance stated:
The 136 kg load specified for impact testing by FMVSS [Federal Motor Vehicle Safety Standard] 301 is relatively small for many trucks. Even with this load directly over the rear axle, the test axle loads will generally not be in the same proportions as the specified GAWRs [gross axle weight ratings] for a full-sized truck. The second sentence allows the manufacturer to conduct the test when the conditions specified in the first sentence cannot be met.
VW recommended that the agency incorporate the load distribution provisions of S7.1.6(b), which apply to multipurpose passenger vehicles, trucks, and buses, in S7.1.6(a), which applies to passenger cars. VW also suggested that the text of S7.1.6(a) and (b) be clarified to state that the weight placement and attachment must be out of the vehicle crush zone and done in a manner that does not interfere with vehicle crash deformation.
GM recommended that the agency revise the test vehicle loading conditions to read as follows:
Passenger cars. A passenger car is loaded to its unloaded vehicle weight plus the weight of the necessary anthropomorphic test devices, plus its rated cargo and luggage capacity weight, secured in the luggage area.
Multipurpose passenger vehicles, trucks, and buses. A multipurpose passenger vehicle, truck, or bus is loaded to its unloaded vehicle weight plus the weight of the necessary anthropomorphic test devices, plus 136 kilograms or its rated cargo and luggage capacity weight, whichever is less, secured in the load carrying area and distributed as nearly as possible in proportion to its gross axle weight ratings. For the purposes of this standard, unloaded vehicle weight does not include the weight of work-performing accessories.
GM also recommended that the agency replace the language in S8.1.1 of Standard No. 208, S6.1 of Standard No. 212, S7.7 of Standard No. 219, S7.1.6 of Standard No. 301, S7.1.6 of Standard No. 303, and S7.2.3 of Standard No. 305 with the same language as that quoted above.  GM stated that these changes would facilitate common understanding, eliminate any ambiguity that might be due to any differences in the language of these standards, parallel the wording of the test procedure, and agree with the agency's intent for the loading conditions to be consistent.
In the NPRM, the agency proposed that the MDB that would be used in the proposed rear impact test procedure upgrade be the same as the one shown in Figure 2 of Standard No. 214, except that the barrier face would be 50 mm (2 inches) lower. The agency requested comments on this proposed change.
DC, GM, and Ford supported the proposed lowering of the barrier face for rear impact testing. The Alliance and VW, however, questioned NHTSA's proposal to lower the barrier face for the rear impact testing. VW commented that the statistics used by NHTSA to justify the proposed change had not been verified. VW also stated,
The speed distribution of rear end crashes in which pre-impact braking might occur has not been fully addressed and it is possible that pre-impact braking of either the target vehicle or the impacting vehicle or both is not as common as NHTSA assumes in the high speed rear impact crashes that the very severe upgraded rear crash test is intended to address.
In the NPRM, the agency noted that the side collision fire rate for passenger cars, light trucks, and vans is highest when a narrow object is struck. Thus, the agency asked whether it would be reasonable to consider a pole side impact test as part of a subsequent upgrading of Standard No. 301.
The Alliance, DC, GM, Ford, and Porsche opposed a pole side impact test. The Alliance stated that NHTSA would need to provide a full assessment of the safety basis if the agency undertook such a rulemaking. The Alliance also stated that the agency would need to propose a detailed test procedure, including pole contact locations, closing velocities, pole sizes, and modes of testing.
DC commented that any potential benefits of a pole side impact test "would be far outweighed by the added counter measures that such testing would require." DC stated:
We believe that the benefits to real world safety and the scope and magnitude, and impact on motor vehicle design of such requirements would need to be verified through detailed studies, testing, and be evaluated by the agency prior to consideration of such potentially invasive regulation with apparent major impact on motor vehicles. We believe that such studies would not demonstrate an appreciable benefit in overall real world occupant safety.
Advocates supported adding a pole side impact test to Standard No. 301. Advocates stated,
Such a test would provide concurrent safety information on both upper and lower interior occupant protection (because of severe side structure deformation and localized intrusion), door integrity both during and after the crash, and of fuel system integrity.
In the NPRM, the agency asked whether it should amend Standard No. 301 to prohibit fuel leakage in any crash test performed under Standard No. 208.
The Alliance and GM supported a future revision limiting fuel system leakage in any Standard No. 208 crash test to current Standard No. 301 requirements, if a meaningful safety benefit could be determined.
DC and Ford opposed a fuel leakage requirement in Standard No. 208 crash tests.
Advocates commented that the rates of fuel release and quantities currently permitted by Standard No. 301 are not consonant with fire prevention and occupant safety following a crash. Advocates recommended that the agency should show the real-world consequences of the rates and amounts of fuel spillage permitted by Standard No. 301, and, if the amounts are judged to be too lenient, revise them to minimize the chances of a post-crash fire.
IIHS and Dynamic Safety recommended that the agency adopt frontal offset crash test requirements in Standard No. 301. IIHS stated, "Frontal offset deformable barrier crash tests create deformation patterns commonly found in severe real-world crashes. The offset loading challenges the vehicle's ability to retain its structural integrity."
In the NPRM, the agency noted that there are a large number of second-stage manufacturers that could be affected by the proposed rule. Second-stage manufacturers buy a chassis from a first-stage manufacturer and finish it to the consumer's specifications. The manufacturers that put a work-related body on a pickup truck chassis (such as a small tow truck) often perform manufacturing operations affecting the fuel system, both in the structure around the fuel tank and where the fuel filler neck attaches to the body. Other second-stage manufacturers use a van chassis or an incomplete vehicle for ambulances, small mobile homes, small school buses, etc.
Typically, the first-stage manufacturer provides the second-stage manufacturer with a body builder's guide that tells the second-stage manufacturer what additions or other modifications it can make and still either pass along the original equipment manufacturer's certification for compliance with Standard No. 301 (for chassis cabs) or otherwise be confident that the vehicle will comply (for other types of incomplete vehicles). To the extent that a second-stage manufacturer deviates from the guide, it would have to certify compliance on its own.
In the NPRM, the agency tentatively concluded that few final stage manufacturers would deviate from the body builder's guide.
The National Truck Equipment Association (NTEA)  disagreed with this tentative conclusion. The NTEA commented:
It is not inconceivable that a major upgrade of the standard could force a chassis manufacturer to forbid the completion of certain chassis with certain body types or equipment in order to reduce their liability to an acceptable level. In any event, it will be impossible for the chassis manufacturers to test or even envision all types of multi-stage vehicles and will likely allow no modifications of any sort while leaving as much liability with the final stage manufacturer as possible, even when no fuel system modifications are made by the final stage manufacturer.
The NTEA stated that the proposed upgrade of Standard No. 301 could require second-stage manufacturers to conduct compliance testing, and that since most second-stage manufacturers are small businesses, such testing would be an unreasonable burden. 
Dynamic Safety, IIHS, and Advocates all raised the issue of fuel siphoning after a fuel line is breached. Dynamic Safety stated:
Any fuel system integrity standard upgrade should address the issue of fuel line siphoning. The standard should require that vehicles not siphon fuel if a fuel line is breached.
Dynamic Safety commented that anti-siphon devices are readily available. Dynamic Safety stated that Ford and DC have been using fuel return line one-way check valves (known as "duckbill valves") on many of their vehicles since the 1980s, and that GM has installed "siphon break" holes in some of its passenger car fuel return lines since the late 1980s.
IIHS stated, "The Institute strongly supports implementation of requirements designed to stop the flow of fuel after a collision." Advocates strongly supported research into and consideration of fuel system flow interdiction through the use of various technologies, such as electric current shut-off devices that stop fuel pump delivery after a crash and manual or electrical inertia switches and check valves to block fuel delivery.
 The members of the Alliance of Automobile Manufacturers are: BMW Group, DaimlerChrysler, Fiat, Ford Motor Company, General Motors, Isuzu, Mazda, Mitsubishi Motors, Nissan, Porsche, Toyota, Volkswagen, and Volvo.
 GM stated, “These evaluations start by first actuating the door latch. Assuming the door unlatches a nominal force of approximately 100 pounds is applied to open the door using a hook-type dial gage. A measurement of how far the door could be opened is made and recorded.”
 The agency notes that it docketed a detailed list of all the rear impact crash test results discussed in the NPRM and other related dockets. See Docket No. NHTSA-99-5825-1, June 8, 1999.
 GM recommended that the following sentence be included in the language for Standard Nos. 208, 212, and 219: “Vehicles are tested to a maximum unloaded vehicle weight of 2,495 kilograms.”
 The NTEA represents second-stage manufacturers, most of whom are small businesses.
 The NTEA submitted several conformity statements from first-stage manufacturers as evidence that the certification responsibilities of second-stage manufacturers would change as a result of this rulemaking.