From: <james.tamm@dot.gov>

To: <Chandana_L._Achanta@omb.eop.gov>

Cc: <rebecca.yoon@dot.gov>, <Steve.Wood@dot.gov>, William Charmley/AA/USEPA/US@EPA, Robi n Moran/AA/USEPA/US@EPA, Ed Nam/AA/USEPA/US@EPA, Stev en Silverman/DC/USEPA/US@EPA

Date: 03/29/2010 02:03 PM Subjec

t: Updated Preamble II G Safety - with expanded footprint discussion



### Chandana,

Attached is the revised Preamble IIG Safety. It includes expanded discussion of < 41 ft2
footprint and a revised footnote relating to the Kahane report (footnote #4).
Jim[attachment "Section II G ‐‐ joint safety section for CAFE

‐ GHG preamble ‐‐ 29 Mar 1240.docx"

deleted by Tad Wysor/AA/USEPA/US]DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

1 G. What are the estimated safety effects of the final MYs 2012-2016

CAFE and GHG standards?

The primary goals of the final CAFE and GHG standards are to reduce fuel consumption and GHG emissions, but in addition to these intended effects, the agencies must consider the potential of the standards to affect vehicle safety 1 , which the agencies have assessed in evaluating the appropriate levels at which to set the final standards. Safety trade-offs associated with fuel economy increases have occurred in the past, andthe agencies must be mindful of the possibility of future ones. These past safety tradeoffs occurred because manufacturers chose, at the time, to build smaller and lighter

vehicles – partly in response to CAFE standards

- rather than adding more expensive fuel-saving technologies (and maintaining vehicle size and safety), and the smaller and lighter vehicles did not fare as well in crashes as larger and heavier vehicles. Historically, as shown in FARS data analyzed by NHTSA, the safest vehicles have been heavy and large, while the vehicles with the highest fatal-crash rates have been light and small, both because the crash rate is higher for small/light vehicles and because the fatality rate per crash is higher for small/light vehicle crashes.

Changes in relative safety are related to shifts in the distribution of vehicles on the road. A policy that induces a widening in the size distribution of vehicles on the road, could result in negative impacts on safety, The primary mechanism in this rulemaking for mitigating the potential negative effects on safe ty is the application of footprint-based standards, which create a disincentive for manufacturers to produce smaller-footprint

vehicles. . This is because as footprint decreases, the corresponding fuel economy/GHG emission target becomes more stringent. 2 The shape of the footprint curves themselves have also been designed to be approximately “footprint neutral” within the sloped portion of the functions – that is, to neither encourage manufacturers to increase the footprint of their fleets, nor to decrease it. Upsizing also is discouraged through a “cut-off” at larger footprints. For both cars and light trucks there is a “cut-off” that affects vehicles smaller than 41 square feet. The agencies recognize that for manufacturers who make small vehicles in this size range, this cut off cr eates some incentive to downsize (i.e. further reduce the size and/or increase the production of models currently smaller than 41 square feet) to make it easier to meet the target. The cut off may also create some incentive for manufacturers who do not currently offer such models to do so in the future. However, at the same time, the agencies believe that there is a limit to the market for cars smaller than

1 In this rulemaking document, vehicle safety is defined as societal fatality rates which include fatalities to occupants of all the vehicles involved in the collisions, plus any pedestrians.

2 We note, however, that vehicle footprint is not synonymous with vehicle size. Since the footprint is only that portion of the vehicle between the front and rear axles, footprint-based standards do not discourage downsizing the portions of a vehicle in front of the front axle and to the rear of the rear axle, or to other portions of the vehicle outside the wheels. The crush space provided by those portions of a vehicle can make important contributions to managing crash energy. At least one manufacturer has confidentially indicated plans to reduce overhang as a way of reducing mass on some vehicles during the rulemaking time frame. Additionally, simply because footprint-based standards create no incentive to downsize vehicles, does not mean that manufacturers may not choose to do so if doing so makes it easier to meet the overall standard (as, for example, if the smaller vehicles are so much lighter that they exceed their targets by much greater amounts). Formatted: Font: Times New

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2 41 square feet - most consumers likely have some minimum expectation about interior volume, among other things. In addition, vehicles in this market segment are the lowest price point for the light-duty automotive market, with a number of models in the $10,000 to $15,000 range. In order to justify selling more vehicles in this market in order to generate fuel economy or CO2 credits (that is, for this final rule to be the incentive for selling more vehicles in this small car segment), a manufacturer would need to add additional technology to the lowest price segment vehicles, which could be challenging. Therefore, due to these two reasons (a likely limit in the market place for the smallest sized cars and the potential consumer acceptance difficulty in adding the necessary technologies in order to generate fuel ec onomy and CO2 credits), the agencies believe that the incentive for manufacturers to increase the sale of vehicles smaller than 41 square feet due to this rulemaking, if present, is small. For further discussion on these aspects of the standards, please see Section II.C above and Chapter 2 of the joint TSD.

Manufacturers have stated, however, that they will reduce vehicle weight as one of the cost-effective means of increasing fuel economy and reducing CO 2 emissions, and the agencies have incorporated this expectation into our modeling analysis supporting today’s final standards. NHTSA’s previous analyses examining the relationship between vehicle mass and fatalities found fatality increases as vehicle weight and size were reduced, but these previous analyses did not differentiate between weight reductions and size ( i.e. , weight and footprint) reductions.

The question of the effect of changes in vehicle mass on safety in the context of fuel economy is a complex question that poses serious analytic challenges and has been a contentious issue for many years, as discusse d by a number of commenters to the NPRM. This contentiousness arises, at least in part, from the difficulty of isolating vehicle mass from other confounding factors ( e.g. , driver behavior, or vehicle factors such as engine size and wheelbase). In addition, several vehicle factors have been closely related historically, such as vehicle mass, wheelbase, and track width. The issue has been reviewed and analyzed in the literature for more than two decades. For the reader’s reference, much more information about safety in the CAFE context is available in Chapter IX of NHTSA’s FRIA. Chapter 7.6 of EPA’s final RIA also contained additional discussion on mass and safety.

Over the past several years, as also discussed by a number of commenters to the NPRM, contention has arisen with regard to the applicability of analysis of historical crash data to future safety effects due to mass reduction. The agencies recognize that there are a host of factors that may make future mass reduction different than what is reflected in the historical data. For one, the footprint-based standards have been carefully developed by the agencies so that they do not encourage vehicle footprint reductions as a way of meeting the standards, but so that they do encourage application of fuel-saving technologies, including mass reduction. This in turn encourages manufacturers to find ways to separate mass reduction from footprint reduction, which will very likely result in a future relationship between mass and fatalities that is safer than the historical relationship. However, as manufacturers pursue these methods of mass reduction, the fleet moves further away from the historical trends, which the agencies recognize. Formatted: Don't adjust space
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3 NHTSA’s NPRM analysis of the safety effects of the proposed CAFE standards was based on NHTSA’s 2003 report concerning mass and size reduction in MYs 1991- 1999 vehicles, and evaluated a “worst-case scenario” in which the safety effects of the

combined reductions of both mass and size for those vehicles were determined for the future passenger car and light truck fleets. 3 In the NPRM analysis, mass and size could not be separated from one another, resulting in what NHTSA recognized was a larger safety disbenefit than was likely under the MYs 2012-2016 footprint-based CAFE standards. NHTSA emphasized, however, that actual fatalities would likely be less than these “worst-case” estimates, and possibly significantly less, based on the various factors discussed in the NPRM that could reduce the estimates, such as careful mass reduction through material substitution, etc.

For the final rule, as discussed in the NPRM and in recognition of the importance of conducting analysis that better reflects, within the limits of our current knowledge, the potential safety effects of future mass reduction in response to the final CAFE and GHG standards that is highly unlikely to involve concurrent reductions in footprint, NHTSA has revised its analysis in consultation with EPA. Perhaps the most important change has been that NHTSA agreed with commenters that it was both possible and appropriate to separate the effect of mass reductions from the effect of footprint reductions. NHTSA thus performed a new statistical analysis, hereafter referred to as the 2010 Kahane analysis, of the MYs 1991-99 vehicle database from its 2003 report (now including rather than excluding 2-door cars in the passenger car fleet), assessing relationships between fatality risk, mass, and footprint for both passenger cars and LTVs (light trucks and vans). 4 As part of its results, the new report presents an “upper-estimate scenario,” a “lower-estimate scenario,” as well as an “ actual regression result scenario ” representing potential safety effects of future mass reductions without corresponding vehicle size reductions, that assume, by virtue of being a cross-sectional analysis of historical data, that historical relationships between vehicle mass and fatalities are maintained. The “upper-estimate scenario” and “lower-estimate scenario” are based on NHTSA’s judgment as a vehicle safety agency, and are not meant to convey any more or less likelihood in the results, but more to convey a sense of bounding for potential safety

effects of reducing mass while holding footprint constant . The upper-estimate scenario reflects potential safety effects given the report’s finding that that, using the one-step regression method of the 2003 Kahane report, the regression coefficients show that mass

3 The analysis excluded 2-door cars.

4 “Relationships Between Fatality Risk, Mass, and Footprint in Model Year 1991-1999 and Other Passenger Cars and LTVs,” Charles J. Kahane, NCSA, NHTSA, March 2010. The text of the report may be found in Chapter IX of NHTSA’s FRIA, where it constitutes a section of that chapter. We note that this report has not yet been externally peer-reviewed, and therefore may be changed or refined after it has been subjected to peer review. The results of the report have not been included in the tables summarizing the costs and benefits of this rulemaking and did not affect the stringency of the standards. NHTSA has begun the process for obtaining peer review in accordance with OMB guidance. The agency will ensure that concerns raised during the peer review process are addressed before relying on the report for future rulemakings. The results of the peer review and any subsequent revisions to the report will be made available in a public docket and on NHTSA’s website as they are completed.. Formatted: Font: Times New Roman, 12 pt, Not Superscript/ Subscript Deleted: unmodified regression

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Model Year 1991-1999 and Other Passenger Cars and LTVs,” Charles J. Kahane, NCSA, NHTSA, March 2010,

available at Docket No. NHTSA-2009- 0059-[item no.]. We note that this reporthas not yet been externally peerreviewed, but that NHTSA had begun the process for peer review in accordance with OMB guidance by the time of publication of this final rule. The results of the peer review and any subsequent revisions to the report will be made available in a public docket and on NHTSA’s website as they are completed.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

4 and footprint each accounted for about half the fatality increase associated with downsizing in a cross-sectional analysis of MYs 1991-1999 cars. A similar effect was found for lighter LTVs. Applying the same regression method to heavier LTVs, however, the coefficients indicated a significant societal fatality reduction when mass, but not footprint, is reduced in the heavier LTVs. 5 Fatalities are reduced primarily

because mass reduction in the heavier LTVs will reduce risk to occupants of the other cars and lighter LTVs involved in collisions with these heavier LTVs. 6 Thus, even in the “upper-estimate scenario,” the potential fatality increases associated with mass reduction in the passenger cars would be to a large extent offset by the benefits of mass reduction in

the heavier LTVs.

The lower-estimate scenario, in turn, reflects NHTSA’s estimate of potential safety effects if future mass reduction is accomplished entirely by through material substitution, smart design, 7 and component integration, among other things, that can reduce mass without perceptibly changing a vehicle’s shape, functionality, or safety performance, maintaining structural strength without compromising other aspects of safety. If future mass reduction follows this path, it could limit the added risk close to only the effects of mass per se (the ability to transfer momentum to other vehicles or objects in a collision), resulting in estimated effects in passenger cars that are substantially smaller than in the upper-estimate scenario based directly on the regression results. The lower-estimate scenario also covers both passenger cars and LTVs.

Overall, based on the new analyses, NHTSA estimated that fatality effects could be markedly less than those estimated in the “worst-case scenario” presented in the NPRM. The agencies believe that the overall effect of mass reduction in cars and LTVs may be close to zero, and may possibly be beneficial in terms of the fleet as a whole if mass reduction is carefully applied in the future (as with careful material substitution and other methods of mass reduction that can reduce mass without perceptibly changing a car’s shape, functionality, or safety performance, and maintain its structural strength without making it excessively rigid). This is especially important if the mass reduction in the heavier LTVs is greater (in absolute terms) than in passenger cars, as discussed further below and in the 2010 Kahane report.

5 Conversely, the coefficients indicate a significant increase if footprint is reduced.

6 We note that there may be some (currently non-quantifiable) welfare losses for purchasers of these heavier LTVs, the mass of which is reduced in response to these final standards. This is due to the fact that in certain crashes, as discussed below and in greater detail in Chapter IX of the NHTSA FRIA, more mass will always be helpful (although certainly in other crashes, the amount of mass reduction modeled by the agency will not be enough to have any significant effect on driver/occupant safety). However, we believe the effects of this will likely be minor. Consumer welfare impacts of the final rule are discussed in more detail in Chapter VIII of the NHTSA FRIA.

7 Manufacturers may reduce mass through smart design using computer aided engineering (CAE) tools that can be used to better optimize load paths within structures by reducing stresses and bending moments applied to structures. This allows better optimization of the sectional thicknesses of structural components to reduce mass while maintaining or improving the function of the component. Smart designs also integrate separate parts in a manner that reduces mass by combining functions or the reduced use of separate fasteners. In addition, some “body on frame” vehicles are redesigned with a lighter “unibody”

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5 The following sections will address how the agencies addressed potential safety effects in the NPRM for the proposed standards, how commenters responded, and the

work that NHTSA has done since the NPRM to revise its estimates of potential safety effects for the final rule. The final section discusses some of the agencies’ plans for the future with respect to potential analysis a nd studies to further enhance our understanding of this important and complex issue.

1. What did the agencies say in the NPRM with regard to potential safety effects?

In the NPRM preceding these final standards, NHTSA’s safety assessment derived from the agency’s belief that some of these vehicle factors, namely vehicle mass and footprint, could not be accurately separated. NHTSA relied on the 2003 study by Dr. Charles Kahane, which estimates the effect of 100-pound reductions in MYs 1991-1999 heavy light trucks and vans (LTVs), light LTVs, heavy passenger cars, and light

passenger cars. 8 The study compares the fatality rates of LTVs and cars to quantify differences between vehicle types, given drivers of the same age/gender, etc. In that analysis, the effect of “weight reduction” is not limited to the effect of mass per se , but includes all the factors, such as length, width, structural strength, safety features, and size of the occupant compartment, that were naturally or historically confounded with mass in MYs 1991-1999 vehicles. The rationale was that adding length, width, or strength to a vehicle historically also made it heavier.

NHTSA utilized the relationships between mass and safety from Kahane (2003), expressed as percentage increases in fatalities per 100-pound mass reduction, and

examined the mass effects assumed in the NPRM modeling analysis. While previous CAFE rulemakings had limited mass reduction as a “technology option” to vehicles over 5,000 pounds GVWR, both NHTSA’s and EPA’s modeling analyses in the NPRM included mass reduction of up to 5-10 percent of baseline curb weight, depending on vehicle subclass, in response to recently-submitted manufacturer product plans as well as public statements indicating that these levels were possible and likely. 5-10 percent represented a maximum bound; EPA’s modeling, for example, included average vehicleweight reductions of 4 percent between MYs 2011 and 2016, although the average pervehicle mass reduction was greater in absolute terms for light trucks than for passenger

cars. NHTSA’s assumptions for mass reduction were also limited by lead time such that mass reductions of 1.5 percent were included for redesigns occurring prior to MY 2014, and mass reductions of 5-10 percent were only “achievable” in redesigns occurring in

MY 2014 or later. NHTSA further assumed that mass reductions would be limited to 5 percent for small vehicles ( e.g. , subcompact passenger cars), and that reductions of 10 percent would only be applied to the larger vehicle types ( e.g. , large light trucks).

8 Kahane, Charles J., Ph.D., “Vehicle Weight, Fatality Risk and Crash Compatibility of Model Year 1991- 99 Passenger Cars and Light Trucks,” DOT HS 809 662, October 2003, Executive Summary. Available at http://www.nhtsa.dot.gov/cars/rules/regrev/evaluate/809662.html (last accessed March 10, 2010).DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

6 Based on these assumptions of how manufacturers might comply with the standards, NHTSA examined the effects of the identifiable safety trends over the lifetimeof the vehicles produced in each model year. The effects were estimated on a year-byyear basis, assuming that certain known safety trends would result in a reduction in the target population of fatalities from which the mass effects are derived. 9 Using this method, NHTSA found a 12.6 percent reduction in fatality levels between 2007 and 2020. The estimates derived from applying Kahane’s 2003 percentages to a baseline of 2007 fatalities were then multiplied by 0.874 to account for changes that the agency believed would take place in passenger car and light truck safety between the 2007 baseline on-road fleet used for that particular analysis and year 2020. 10

NHTSA and EPA both emphasized that the safety effect estimates in the NPRM needed to be understood in the context of the 2003 Kahane report, which is based upon a cross-sectional analysis of the actual on-road safety experience of 1991-1999 vehicles. For those vehicles, heavier usually also meant larger-footprint. Hence, the numbers in those analyses were used to predict the safety-related fatalities that could occur in the unlikely event that weight reduction for MYs 2012-2016 is accomplished entirely by reducing mass and reducing footprint. Any estimates derived from those analyses represented a “worst-case” estimate of safety effects, for several reasons.

First, manufacturers are far less likely to reduce mass by “downsizing” (making vehicles smaller overall) under the current attribute-based standards, because the standards are based on vehicle footprint. The selection of footprint as the attribute in setting CAFE and GHG standards helps to reduce the incentive to alter a vehicle’s physical dimensions. This is because as footprint decreases, the corresponding fuel economy/GHG emission target becomes more stringent. 11 The shape of the footprint

9 NHTSA explained that there are several identifiable safety trends that are already in place or expected to occur in the foreseeable future and that were not accounted for in the study. For example, two important new safety standards that have already been issued and will be phasing in during the rulemaking time frame. Federal Motor Vehicle Safety Standard No. 126 (49 CFR 571.126) will require electronic stability control in all new vehicles by MY 2012, and the upgrade to Federal Motor Vehicle Safety Standard No. 214 (Side Impact Protection, 49 CFR 571.214) will likely result in all new vehicles being equipped with head-curtain air bags by MY 2014. 9 Additionally, the agency stated that it anticipates continued improvements in driver (and passenger) behavior, such as higher safety belt use rates. All of these will tend to reduce the absolute number of fatalities resulting from mass reductions. Thus, while the percentage increases in Kahane (2003) was applied, the reduced base resulted in smaller absolute increases than those that were predicted in the 2003 report.

10 Blincoe, L. and Shankar, U, “The Impact of Safety Standards and Behavioral Trends on Motor Vehicle Fatality Rates,” DOT HS 810 777, January 2007. See Table 4 comparing 2020 to 2007 (37,906/43,363 = 12.6% reduction (1-.126 = .874)

11 We note, however, that vehicle footprint is not synonymous with vehicle size. Since the footprint is only that portion of the vehicle between the front and rear axles, footprint-based standards do not discourage downsizing the portions of a vehicle in front of the front axle and to the rear of the rear axle, or to other portions of the vehicle outside the wheels. The crush space provided by those portions of a vehicle can make important contributions to managing crash energy. NHTSA noted in the NPRM that at least one manufacturer has confidentially indicated plans to reduce overhang as a way of reducing mass on some vehicles during the rulemaking time frame. Additionally, simply because footprint-based standards create no incentive to downsize vehicles, does not mean that manufacturers may not choose to do so if doing so Formatted: Font color: Black, Not Superscript/ Subscript

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7 curves themselves have also been designed to be approximately “footprint neutral” within the sloped portion of the functions – that is, to neither encourage manufacturers to increase the footprint of their fleets, nor to decrease it. For further discussion on these aspects of the standards, please see Section II.C above and Chapter 2 of the joint TSD. However, as discussed in Sections III.H.1 and IV.G.6 below, the agencies acknowledge some uncertainty regarding how consumer purchases will change in response to the vehicles designed to meet the MYs 2012-2016 st andards. This could potentially affect the mix of vehicles sold in the future, including the mass and footprint distribution.

As a result, the agencies found it likely that a significant portion of the mass reduction in the MY 2012-2016 vehicles would be accomplished by strategies, such as material substitution, smart design, reduced powertrain requirements 12 , and mass compounding, that have a lesser safety effect than the prevalent 1980s strategy of simply making the vehicles smaller. The agencies noted that to the extent that future mass reductions could be achieved by these methods—without any accompanying reduction in the size or structural strength of the vehicle—then the fatality increases associated with the mass reductions anticipated by the model as a result of the proposed standards could be significantly smaller than those in the worst-case scenario.

However, even though the agencies recognized that these methods of mass reduction could be technologically feasible in the rulemaking time frame, and included them as such in our modeling analyses, the agencies diverged as to how potential safety effects accompanying such methods of mass reduction could be evaluated, particularly in relation to the worst-case scenario presented by NHTSA. NHTSA stated that it could not predict how much smaller those increases would be for any given mixture of mass reduction methods, since the data on the safety effects of mass reduction alone (withoutsize reduction) was not available due to the low numbers of vehicles in the current onroad fleet that have utilized these technologies extensively. Further, to the extent that mass reductions were accomplished through use of light, high-strength materials, NHTSA emphasized that there would be significant additional costs that would need to be determined and accounted for than were reflected in the agency’s proposal.

Additionally, NHTSA emphasized that while it thought material substitution and other methods of mass reduction could considerably lessen the potential safety effects compared to the historical trend, NHTSA also stated that it did not believe the effects in passenger cars would be smaller than zero. EPA disagreed with this, and stated in the NPRM that the safety effects could very well be smaller than zero. Even though footprint-based standards discourage downsizing as a way of “balancing out” sales of larger/heavier vehicles, they do not discourage manufacturers from reducing crush space

makes it easier to meet the overall standard (as, for example, if the smaller vehicles are so much lighter that they exceed their targets by much greater amounts).

12 Reduced powertrain requirements do not include a reduction in performance. When vehicle mass is reduced, engine torque and transmission gearing can be altered so that acceleration performance is held constant instead of improving. A detailed discussion is included in Chapter 3 of the Technical Support

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8 in overhang areas or from reducing structural support as a way of taking out mass. 13
Moreover, NHTSA’s analysis had also found that lighter cars have a higher involvement rate in fatal crashes, even after controlling for the driver’s age, gender, urbanization, and region of the country. Being unable to explain this clear trend in the crash data, NHTSAstated that it must assume that mass reduction is likely to be associated with higher fatalcrash rates, no matter how the weight reduction is achieved.

NHTSA also noted in the NPRM that several studies by Dynamic Research, Inc. (DRI) had been repeatedly cited to the agency in support of the proposition that reducing vehicle mass while maintaining track width and wheelbase would lead to significant safety benefits. In its 2005 studies, one of which was published and peer-reviewed through the Society of Automotive Engineers as a technical paper, DRI attempted to assess the independent effects of vehicle weight and size (in terms of wheelbase and track width) on safety, and presented results indicating that reducing vehicle weight tends to reduce fatalities, but that reducing vehicle wheelbase and track width tends to increase fatalities. DRI’s analysis was based on FARS data for MYs 1985-1998 passenger cars and 1985-1997 light trucks, similar to the MYs 1991-1999 car and truck data used in the 2003 Kahane report. However, DRI included 2-door passenger cars, while the 2003 Kahane report excluded those vehicles out of concern that their inclusion could bias the results of the regression analysis, because a significant proportion of MYs 1991-1999 2- door cars were sports and “muscle” cars, which have particularly high fatal crash rates for their relatively short wheelbases compared to the rest of the fleet. While in the NPRM NHTSA rejected the results of the DRI studies based in part on this concern, the agencies note that upon further consideration, NHTSA has agreed for this final rule that the inclusion of 2-door cars in regression analysis of historical data is appropriate, and indeed has no overly-biasing effects.

The 2005 DRI studies also differed from the 2003 Kahane report in terms of their estimates of the effect of vehicle weight on rollover fatalities. The 2003 Kahane report analyzed a single variable, curb weight, as a surrogate for both vehicle size and weight, and found that curb weight reductions would increase rollover fatalities. The DRI study, in contrast, attempted to analyze curb weight, wheelbase, and track width separately, and found that curb weight reduction would decrease rollover fatalities, while wheelbase reduction and track width reduction would increase them. DRI suggested that heavier vehicles may have higher rollover fatalities for two reasons: first, because taller vehicles tend to be heavier, so the correlation between vehicle height and weight and vehicle center-of-gravity height may make heavier vehicles more rollover-prone; and second, because heavier vehicles may have been less rollover-crashworthy due to FMVSS No. 216’s constant (as opposed to proportional) requirements for MYs 1995-1999 vehicles weighing more than 3,333 lbs unloaded.

Overall, DRI’s 2005 studies found a reduction in fatalities for cars (580 in the first study, and 836 in the second study) and for trucks (219 in the first study, 682 in the second study) for a 100 pound reduction in curb weight without accompanying wheelbase

13 However, we recognize that FMVSS and NCAP ratings may limit the manufacturer’s ability to reduce crush space or structural support.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

9 or track width reductions. In the NPRM, NHTSA disagreed with the results of the DRI studies, out of concern that DRI’s inclusion of 2-door cars in its analysis biased the results, and because NHTSA was unable to reproduce DRI’s results despite repeated attempts. NHTSA stated that it agreed intuitively with DRI’s conclusion that vehicle mass reductions without accompanying size re ductions (as through substitution of a heavier material for a lighter one) would be less harmful than downsizing, but without supporting real-world data and unable to verify DRI’s results, NHTSA stated that it could not conclude that mass reductions would result in safety benefits. EPA, in contrast, believed that DRI’s results contained some merit, in particular because the study separated the effects of mass and size and EPA stated that applying them using the curb weight reductions in EPA’s modeling analysis would show an overall reduction of fatalities for the proposed standards.

On balance, both agencies recognized that mass reduction could be an important tool for achieving higher levels of fuel economy and reducing CO 2 emissions, and emphasized that NHTSA’s fatality estimates represented a worst-case scenario for the potential effects of the proposed standards, and that actual fatalities will be less than these estimates, possibly significantly less, based on the various factors discussed in the NPRM that could reduce the estimates. The agencies sought comment on the safety analysis and discussions presented in the NPRM.

2. What public comments did the agencies receive on the safety analysis

and discussions in the NPRM?

Several dozen commenters addressed the safety issue. Claims and arguments made by commenters in response to the safety effects analysis and discussion in the NPRM tended to follow several general themes, as follows:

• NHTSA’s safety effects estimates are inaccurate because they do not account for:

o While NHTSA’s study only considers vehicles from MYs 1991-1999, more recently-built vehicles are safer than those, and future vehicles will be safer still;

o Lighter vehicles are safer than heavier cars in terms of crash-avoidance, because they handle and brake better;

o Fatalities are linked more to other factors than mass;

o The structure of the standards reduces/contributes to potential safety effects from mass reduction;

o NHTSA could mitigate additional safety effects from mass reduction, if there are any, by simply regulating safety more;

o Casualty risks range widely for vehicles of the same weight or footprint, which skews regression analysis and makes computer simulation a better predictor of the safety effects of mass reduction;

• DRI’s analysis shows that lighter vehicles will save lives, and NHTSA reaches the opposite conclusion without disproving DRI’s analysis;

o Possible r easons that NHTSA and DRI have reached different

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10  NHTSA’s study should distinguish between reductions in size and reductions in weight like DRI’s;

 NHTSA’s study should include two-door cars;

 NHTSA’s study should have used different assumptions;

 NHTSA’s study should incl ude confidence intervals;

• NHTSA should include a “best-case” estimate in its study;

• NHTSA should not include a “worst-case” estimate in its study;

The agencies recognize that the issue of the potential safety effects of mass reduction, which was one of the many factors considered in the balancing that led to the agencies’ conclusion as to appropriate stringency levels for the MYs 2012-2016 standards, is of great interest to the public and could possibly be a more significant factor in regulators’ and manufacturers’ decisions with regard to future standards beyond MY 2016. The agencies are committed to analyzing this issue thoroughly and holistically going forward, based on the best available science, in order to further their closely related missions of safety, energy conservation, and environmental protection. We respond to

the issues and claims raised by commenters in turn below.

NHTSA’s estimates are inaccurate because NHTSA’s study only considers vehicles from MYs 1991-1999, but more recently-built vehicles are safer than those, and future vehicles will be safer still

A number of commenters (CAS, Adcock, NACAA, NJ DEP, NY DEC, UCS, and Wenzel) argued that the 2003 Kahane report, on which the “worst-case scenario” in the NPRM was based, is outdated because it considers the relationship between vehicle weight and safety in MYs 1991-1999 passenger cars. These commenters generally stated that data from MYs 1991-1999 vehicles provide an inaccurate basis for assessing the relationship between vehicle weight and safety in current or future vehicles, because the fleets of vehicles now and in the future are increasingly different from that 1990s fleet (more crossovers, fewer trucks, lighter trucks , etc.), with different vehicle shapes and characteristics, different materials, and more safety features. Several of these commenters argued that NHTSA should conduct an updated analysis for the final rule using more recent data – Wenzel, for example, stated that an updated regression analysis that accounted for the recent introduction of crossover SUVs would likely find reduced casualty risk, similar to DRI’s previous finding using fatality data. CEI, in contrast, argued that the “safety trade-off” would not be eliminated by new technologies and attribute-based standards, because additional weight inherently makes a vehicle safer to its own occupants, citing the 2003 Kahane report, while AISI argued that Desapriya had found that passenger car drivers and occupants are two times more likely to be injured than drivers and occupants in larger pickup trucks and SUVs.

Several commenters (Adcock, CARB, Daimler, NESCAUM, NRDC, Public Citizen, UCS, Wenzel) suggested that NHTSA’s analysis was based on overly pessimistic assumptions about how manufacturers would choose to reduce mass in their vehicles, because manufacturers have a strong incentive in the market to build vehicles safely. Many of these commenters stated that several manufacturers have already Formatted: Not Superscript/ Subscript

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11 committed publicly to fairly ambitious mass reduction goals in the mid-term, but several

stated further that NHTSA should not assume that manufacturers will reduce the same amount of mass in all vehicles, because it is likely that they will concentrate mass reduction in the heaviest vehicles, which will improve compatibility and decrease aggressivity in the heaviest vehicles. Daimler emphasized that all vehicles will have to comply with the Federal Motor Vehicle Safety Standards, and will likely be designed to

test well in NHTSA’s NCAP tests.

Other commenters (Aluminum Association, CARB, CAS, ICCT, MEMA, NRDC, U.S. Steel) also emphasized the need for NHTSA to account for the safety benefits to be expected in the future from use of advanced materials for lightweighting purposes and other engineering advances. The Aluminum Association stated that advanced vehicle design and construction techniques using aluminum can improve energy management and minimize adverse safety effects of their use, 14 but that NHTSA’s safety analysis could not account for those benefits if it were based on MYs 1991-1999 vehicles. CAS, ICCT,

and U.S. Steel discussed similar benefits for more recent and future vehicles built with high strength steel (HSS), although U.S. Steel cautioned that given the stringency of the proposed standards, manufacturers would like ly be encouraged to build smaller and lighter vehicles in order to achieve compliance, which fare worse in head-on collisions than larger, heavier vehicles. AISI, in contrast to U.S. Steel, stated that in its research with the Auto/Steel Partnership and in programs supported by DOE, it had found that the use of new Advanced HSS steel grades could enable mass of critical crash structures, such as front rails and bumper systems, to be reduced by 25 percent without degrading performance in standard NHTSA frontal or IIHS offset instrumented crash tests compared to their “heavier counterparts.”

Agencies’ response:

NHTSA, in consultation with EPA and DOE, plans to begin updating the MYs 1991-1999 database on which NHTSA’s safety analyses in the NPRM and final rule are based in the next several months in order to analyze the differences in safety effects against vehicles built in more recent model years. As this task will take at least a year to complete, beginning it immediately after the NPRM would not have enabled the agency to complete it and then conduct a new analysis during the period between the NPRM and

the final rule.

For purposes of this final rule, however, we believe that using the same MYs 1991-1999 database as that used in the 2003 Kahane study provides a reasonable basis for attempting to estimate safety effects due to reductions in mass. While commenters often stated that updating the database would help to reveal the effect of recently-introduced

14 The Aluminum Association (NHTSA-2009-0059-0067.3) stated that its research on vehicle safety compatibility between an SUV and a mid-sized car, done jointly with DRI, shows that reducing the weight of a heavier SUV by 20% (a realistic value for an aluminum-intensive vehicle) could reduce the combined injury rate for both vehicles by 28% in moderately severe crashes. The commenter stated that it would keep NHTSA apprised of its results as its research progressed. Based on the information presented, NHTSA believes that this research appears to agree with NHTSA’s latest analysis, which finds that a reduction in weight for the heaviest vehicles may improve overall fleet safety.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

12 lightweight vehicles with extensive material substitution, there have in fact not yet been a significant number of vehicles with substantial mass reduction/material substitution to analyze, and they must also show up in the crash databases for NHTSA to be able to add them to its analysis. Based on NHTSA’s research, specifically, on three statistical analyses over a 12-year period (1991-2003) covering a range of 22 model years (1978- 1999), NHTSA believes that the relationships between mass, size, and safety has only changed slowly over time, although we recognize that they may change somewhat more rapidly in the future. 15 As the on-road fleet gains increasing numbers of vehicles with increasing amounts of different methods of mass reduction applied to them, we may begin to discern changes in the crash databases due to the presence of these vehicles, but any such changes are likely to be slow and evolutionary, particularly in the context of MYs 2000-2009 vehicles. The agencies do expect that further analysis of historical data files will continue to provide a robust and practicable basis for estimating the potential safety effects that might occur with future reductions in vehicle mass. However, we recognize that estimates derived from analysis of historical data, like estimates from any other type of analysis (including simulation-based analysis, which cannot feasibly cover all relevant scenarios), will be uncertain in terms of predicting actual future outcomes with respect to a vehicle fleet, driving population, and operating environment that does not yet exist.

The agencies also recognize that more recent vehicles have more safety features than 1990s vehicles, which are likely to make them safer overall. To account for this, NHTSA did adjust the results of both its NPRM and final rule analysis to include known safety improvements, like ESC and increases in seat belt use, that have occurred since

MYs 1991-1999. 16 However, simply because newer vehicles have more safety countermeasures, does not mean that the weight/safety relationship necessarily changes. More likely, it would change the target population (the number of fatalities) to which one would apply the weight/safety relationship. Thus, we still believe that some mass reduction techniques for both passenger cars and light trucks can make them less safe, in certain crashes as discussed in NHTSA’s FRIA, than if mass had not been reduced. 17

As for NHTSA’s assumptions about mass reduction, in its analysis, NHTSA generally assumed that lighter vehicles could be reduced in weight by 5 percent while heavier light trucks could be reduced in weight by 10 percent. NHTSA recognizes that manufacturers might choose a different mass reduction scheme than this, and that its

15 NHTSA notes the CAS’ comments regarding changes in the vehicle fleets since the introduction of CAFE standards in the late 1970s, but believes they apply more to the differences between late 1970s through 1980s vehicles and 2010s vehicles than to the differences between 1990s and 2010s vehicles. NHTSA believes that the CAS comments regarding the phase-out of 1970s vehicles and their replacement with safer, better fuel-economy-achieving 1980s vehicles paint with rather too large a brush to be relevant to the main discussion of whether the 2003 Kahane report database can reasonably be used to estimate safety effects of mass reduction for the MYs 2012-2016 fleet.

16 See NHTSA FRIA Chapter IX.

17 If one has a vehicle (vehicle A), and both reduces the vehicle’s mass and adds new safety equipment to it, thus creating a variant (vehicle A 1 ), the variant might conceivably have a level of overall safety for its occupants is equal to that of the original vehicle (vehicle A). However, vehicle A 1 might not be as safe as second variant (vehicle A 2 ) of vehicle A, one that is produced by adding to vehicle A the same new safety equipment added to the first variant, but this time without any mass reduction.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

13 quantification of the estimated effect on safety would be different if they did. We emphasize that our estimates are based on the assumptions we have employed and are intended to help the agency consider the potential effect of the final standards on vehicle safety. Thus, based on the 2010 Kahane analysis, reductions in weight for the heavier light trucks would have positive overall safety effects, 18 while mass reductions for passenger cars and smaller light trucks woul d have negative overall safety effects.

NHTSA’s estimates are inaccurate because they do not account for the fact that lighter vehicles are safer than heavier cars in terms of crash-avoidance, because they handle and brake better

ICCT stated that lighter vehicles are better able to avoid crashes because they“handle and brake slightly better,” arguing that size-based standards encourage lighterweight car-based SUVs with “significantly better handling and crash protection” than 1996-1999 mid-size SUVs, which will reduce both fatalities and fuel consumption. ICCT stated that NHTSA did not include these safety benefits in its analysis. DRI also stated that its 2005 report found that crash avoidance improves with reduction in curb weight and/or with increases in wheelbase and track, because “Crash avoidance can depend, amongst other factors, on the vehicle directional control and rollover characteristics.” DRI argued that, therefore, “These results indicate that vehicle weight reduction tends to decrease fatalities, but vehicle wheelbase and track reduction tends to increase fatalities.”

Agencies’ response:

In fact, NHTSA’s regression analysis of crash fatalities per million registration years measures the effects of crash avoidance, if there are any, as well as crashworthiness. Given that the historical empirical data for passenger cars show a trend of higher crash rates for lighter cars, it is unclear whether lighter cars have, in the net, superior crash avoidance, although the agencies recognize that they may have advantages in certain individual situations. EPA presents a discussion of improved accident avoidance as vehicle mass is reduced in Chapter 7.6 of its final RIA. The important point to emphasize is that it depends on the situation – it would oversimplify drastically to point to one situation in which extra mass helps or hurts and then extrapolate effects for crash avoidance across the board based on only that.

For example, the relationship of vehicle mass to rollover and directional stability is more complex than commenters imply. For rollover, it is true that if heavy pickups were always more top-heavy than lighter pi ckups of the same footprint, their higher center of gravity could make them more rollover-prone, yet some mass can be placed so as to lower a vehicle’s center of gravity and make it less rollover-prone. For mass reduction to be beneficial in rollover crashes, then, it must take center of gravity height into account along with other factors such as passenger compartment design and structure, suspension, the presence of various safety equipment, and so forth.

18 This is due to the beneficial effect on the occupants of vehicles struck by the downweighted larger

vehicles.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

14 Similarly, for directional stability, it is true that having more mass increases the “understeer gradient” of cars – i.e. , it reinforces their tendency to proceed in a straight line and slows their response to steering input, which would be harmful where prompt steering response is essential, such as in a double-lane-change maneuver to avoid an obstacle. Yet more mass and a higher understeer gradient could help when it is better to remain on a straight path, such as on a straight road with icy patches where wheel slip might impair directional stability. Thus, while less vehicle mass can sometimes improve crash avoidance capability, there can also be situations when more vehicle mass can help

in other kinds of crash avoidance.

Further, NHTSA’s research suggests that additional vehicle mass may be even more helpful, as discussed in Chapter IX of NHTSA’s FRIA, when the average driver’s response to a vehicle’s maneuverability is taken into account. Lighter cars have historically (1976-2009) had higher collision-involvement rates than heavier cars – even in multi-vehicle crashes where directional and rollover stability is not particularly an

issue. 19 Based on our analyses using nationally- collected FARS and GES data, drivers of lighter cars are more likely to be the culpable party in a 2-vehicle collision, even after controlling for footprint, the driver’s age, gender, urbanization, and region of the country.

Thus, based on this data, it appears that lighter cars may not be driven as well as heavier cars, although it is unknown why this is so. If poor drivers intrinsically chose light cars (self-selection), it might be evidenced by an increase in antisocial driving behavior (such as DWI, drug involvement, speeding, or driving without a license) as car weight decreases, after controlling for driver age and gender – in addition to the increases in merely culpable driver behavior (such as failure to yield the right of way). But analyses in NHTSA’s 2003 report did not show an increase in antisocial driver behavior in the lighter cars paralleling their increase in culpable involvements.

NHTSA also hypothesizes that certain aspects of lightness and/or smallness in a car may give a driver a perception of greater maneuverability that ultimately results in driving with less of a “safety margin,” e.g. , encouraging them to weave in traffic. That may appear paradoxical at first glance, as ma neuverability is, in the abstract, a safety plus. Yet the situation is not unlike powerful engines that could theoretically enable a driver to escape some hazards, but in reality have long been associated with high crash and fatality rates. 20

19 See

, e.g. , NHTSA (2000). Traffic Safety Facts 1999. Report No. DOT HS 809 100. Washington, DC: National Highway Traffic Safety Administration, p. 71; Najm, W.G., Sen, B., Smith, J.D., and Campbell, B.N. (2003). Analysis of Light Vehicle Crashes and Pre-Crash Scenarios Based on the 2000 General Estimates System, Report No. DOT HS 809 573. Washington, DC: National Highway Traffic Safety Administration, p. 48.

20 Robertson, L.S. (1991), “How to Save Fuel and Reduce Injuries in Automobiles,” The Journal of

Trauma , Vol. 31, pp. 107-109; Kahane, C.J. (1994). Correlation of NCAP Performance with Fatality Risk in Actual Head-On Collisions, NHTSA Technical Report No. DOT HS 808 061. Washington, DC: National Highway Traffic Safety Administration, http://www-nrd.nhtsa.dot.gov/Pubs/808061.PDF, pp. 4-

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15 NHTSA’s estimates are inaccurate because fatalities are linked more to other factors than mass

Tom Wenzel stated that the safety record of recent model year crossover SUVs indicates that weight reduction in this class of vehicles (small to mid-size SUVs) resulted in a reduction in fatality risk. Wenzel argued that NHTSA should acknowledge that other vehicle attributes may be as important, if not more important, than vehicle weight or footprint in terms of occupant safety, such as unibody construction as compared to ladder-frame, lower bumpers, and less rigid frontal structures, all of which make crossover SUVs more compatible with cars than truck-based SUVs.

Marc Ross commented that fatalities are linked more strongly to intrusion than to mass, and stated that research by safety experts in Japan and Europe suggests the main cause of serious injuries and deaths is intrusion due to the failure of load-bearing elements to properly protect occupants in a severe crash. Ross argued that the results from this project have “overturned the original views about compatibility,” which thought that mass and the mass ratio were the dominant factors. Since footprint-based standards will encourage the reduction of vehicle weight through materials substitution while maintaining size, Ross stated, they will help to reduce intrusion and consequently fatalities, as the lower weight reduces crash forces while maintaining size preserves crush space. Ross argued that this factor was not considered by NHTSA in its discussion of safety. ICCT agreed with Ross’ comments on this issue.

In previous comments on NHTSA rulemakings and in several studies, Wenzel and Ross have argued generally that vehicle design and “quality” is a much more important determinant of vehicle safety than mass. In comments on the NPRM, CARB, NRDC, Sierra Club, and UCS echoed this theme.

ICCT commented as well that fatality rates in the EU are much lower than rates in the U.S., even though the vehicles in the EU fleet tend to be smaller and lighter than those in the U.S. fleet. Thus, ICCT argued, “This strongly supports the idea that vehicle and highway design are far more important factors than size or weight in vehicle safety.” ICCT added that “It also suggests that the rise in SUVs in the U.S. has not helped reduce fatalities.” CAS also commented that Germany’s vehicle fleet is both smaller and lighter than the American fleet, and has lower fatality rates.

Agencies’ response:

NHTSA and EPA agree that there are many features that affect safety. While crossover SUVs have lower fatality rates than truck-based SUVs, there are no analyses that attribute the improved safety to mass alone , and not to other factors such as the lower center of gravity or the unibody construction of these vehicles. While a number of improvements in safety can be made, they do not negate the potential that another 100 lbs. could make a passenger car or crossover vehicle safer for its occupants, because of the effects of mass per se as discussed in NHTSA’s FRIA, albeit similar mass reductions could make heavier LTVs safer to other vehicles without necessarily harming their ownDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

16 drivers and occupants. Moreover, in the 2004 response to docket comments, NHTSA explained that the significant relationship between mass and fatality risk persisted even after controlling for vehicle price or nameplat e, suggesting that vehicle “quality” as cited by Wenzel and Ross is not necessarily more important than vehicle mass.

As for reductions in intrusions due to material substitution, the agencies agree generally that the use of new and innovative materials may have the potential to reduce crash fatalities, but such vehicles have not been introduced in large numbers into the vehicle fleet. The agencies will continue to monitor the situation, but ultimately the effects of different methods of mass reduction on overall safety in the real world (not just in simulations) will need to be analyzed when vehicles with these types of mass reduction are on the road in sufficient quantities to provide statistically significant results. For example, a vehicle that is designed to be much stiffer to reduce intrusion is likely to have a more severe crash pulse and thus impose greater forces on the occupants during a crash, and might not necessarily be good for elderly and child occupant safety in certain types of crashes. Such trade-offs make it difficult to estimate overall results accurately without real world data. The agencies will continue to evaluate and analyze such real world data as it becomes available, and will keep the public informed as to our progress.

ICCT’s comment illustrates the fact that different vehicle fleets in different countries can face different challenges. NHTSA does not belie ve that the fact that the EU vehicle fleet is generally lighter than the U.S. fleet is the exclusive reason, or even the primary factor, for the EU’s lower fatality rates. The data ICCT cites do not account for s ignificant

differences between the US and EU such as in belt usage, drunk driving, rural/urban roads, driving culture, etc.

The structure of the standards reduces/contributes to potential safety risks from

mass reduction

Since switching in 2006 to setting attribute-based light truck CAFE standards, NHTSA has emphasized that one of the benefits of a footprint-based standard is that it discourages manufacturers from building smaller, less safe vehicles to achieve CAFE compliance by “balancing out” their larger vehicles, and thus avoids a negative safety consequence of increasing CAFE stringency. 21 Some commenters on the NPRM (Daimler, IIHS, NADA, NRDC, Sierra Club et al. ) agreed that footprint-based standards would protect against downsizing and help to mitigate safety risks, while others stated that there would still be safety risks even with footprint-based standards – CEI, for example, argued that mass reduction inherently creates safety risks, while IIHS and Porsche expressed concern about footprint-ba sed standards encouraging manufacturers to manipulate wheelbase, which could reduce crush space and worsen vehicle handling. U.S. Steel and AISI both commented that the “aggressive schedule” for the proposed

21 We note that commenters were divided on whether they believed there was a clear correlation between vehicle size/weight and safety (CEI, Congress of Racial Equality, Heritage Foundation, IIHS, Spurgeon, University of PA Environmental Law Project) or whether they believed that the correlation was less clear, for example because they believed that vehicle design was more important than vehicle mass (CARB, Public Citizen). Formatted: Normal, Indent: First line: 0 pt, Don't adjust space
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17 increases in stringency could encourage manufacturers to build smaller, lighter vehicles in order to comply.

Some commenters also focused on the shape and stringency of the target curves and their potential effect on vehicle safety. IIHS agreed with the agencies’ tentative decision to cut off the target curves at the small-footprint end. Regarding the safety effect of the curves requiring less stringent targets for larger vehicles, while IIHS stated that increasing footprint is good for safety, CAS, Wenzel, and the UCSB students stated that decreasing footprint may be better for safety in terms of risk to occupants of other vehicles. Daimler, Wenzel, and the University of PA Environmental Law Project commented generally that more similar passenger car and light truck targets at identical footprints (as Wenzel put it, a single target curve) would improve fleet compatibility and thus, safety, by encouraging manufacturers to build more passenger cars instead of light

trucks.

Agencies’ response:

The agencies continue to believe that footprint-based standards help to mitigate potential safety risks from downsizing if the target curves maintain sufficient slope,because, based on NHTSA’s analysis, larger-footprint vehicles are safer than smallerfootprint vehicles. 22 The structure of the footprint-based curves will also discourage the upsizing of vehicles. Nevertheless, we recognize that footprint-based standards are not a panacea – NHTSA’s analysis continues to show that there was a historical relationship between lower vehicle mass and increased safety risk in passenger cars even if footprint is maintained, and there are ways that manufacturers may increase footprint that either improve or reduce vehicle safety, as indicated by IIHS and Porsche.

With regard to whether the agencies should set separate curves or a single one,

NHTSA also notes in Section II.C that EPCA requires NHTSA to establish standards separately for passenger cars and light trucks, and thus concludes that the standards for each fleet should be based on the characteristics of vehicles in each fleet. In other words, the passenger car curve should be based on the characteristics of passenger cars, and the light truck curve should be based on the characteristics of light trucks—thus to the extent that those characteristics are different, an artificially-forced convergence would not accurately reflect those differences. However, such convergence could be appropriate depending on future trends in the light vehicle market, specifically further reduction in the differences between passenger car and light truck characteristics. While that trend was more apparent when car-like 2WD SUVs were classified as light trucks, it seems likely to diminish for the model year vehicles subject to these rules as the truck fleet will be more purely “truck-like” than has been the case in recent years.

NHTSA’s estimates are inaccurate because NHTSA could mitigate additional safety risks from mass reduction, if there are any, by simply regulating safety

more

22 See Chapter IX of NHTSA’s FRIA. Formatted: Normal, Don't adjust space between Latin and Asian text, Don't adjust space between Asian

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in relation to concerns about the feasibility of attribute-based standards as applied to manufacturers emphasizing small vehicles, IIHS’s comments suggest

IIHS is not concerned with the standards’ resultant neutrality with respect to

incremental reductions in the size of the

smallest vehicles.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

18 Since NHTSA began considering the potential safety risks from mass reduction in response to increased CAFE standards, some commenters have suggested that NHTSA could mitigate those safety risks, if any, by simply regulating more. 23 In response to the safety analysis presented in the NPRM, several commenters stated that NHTSA should develop additional safety regulations to require vehicles to be designed more safely, whether to improve compatibility (Adcock, NY DEC, Public Citizen, UCS), to require seat belt use (CAS, UCS), to improve rollover and roof crush resistance (UCS), or to improve crashworthiness generally by strengthening NCAP and the star rating system (Adcock). Wenzel commented further that “Imp rovements in safety regulations will have a greater effect on occupant safety than FE standards that are structured to maintain, but may actually increase, vehicle size.”

Agencies’ response:

NHTSA appreciates the commenters’ suggestions and notes that the agency is continually striving to improve motor vehicle safety consistent with its mission. As noted above, improving safety in other areas affects the target population that the mass/footprint relationship could affect, but it does not necessarily change the relationship.

The 2010 Kahane analysis discussed in this final rule evaluates the relative safety risk when vehicles are made lighter than th ey might otherwise be absent the final MYs 2012-2016 standards. It does consider the effect of known safety regulations as they are projected to affect the target population.

Casualty risks range widely for vehicles of the same weight or footprint, which skews regression analysis and makes computer simulation a better predictor of the safety effects of mass reduction

Wenzel commented that he had found, in his most recent work, after accounting for drivers and crash location, that there is a wide range in casualty risk for vehicles with the same weight or footprint. Wenzel stated that for drivers, casualty risk does generally decrease as weight or footprint increases, especially for passenger cars, but the degree of variation in the data for vehicles (particularly light trucks) at a given weight or footprint makes it difficult to say that a decrease in weight or footprint will necessarily result in increased casualty risk. In terms of risk imposed on the drivers of other vehicles, Wenzel stated that risk increases as light truck weight or footprint increases.

Wenzel further stated that because a regression analysis can only consider the average trend in the relationship between vehicle weight/size and risk, it must “ignore” vehicles that do not follow that trend. Wenzel therefore recommended that the agency employ computer crash simulations for analyzing the effect of vehicle weight reduction on safety, because they can “pinpoint the effect of specific vehicle designs on safety,” and can model future vehicles which do not yet exist and are not bound to analyzing historical data. Wenzel cited, as an example, a DRI simulation study commissioned by

23 See, e.g. , MY 2011 CAFE final rule, 74 Fed. Reg. at 14403-05 (Mar. 30, 2009).DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

19 the Aluminum Association (Kebschull 2004), which used a computer model to simulate the effect of changing SUV mass or footprint (without changing other attributes of the vehicle) on crash outcomes, and showed a 15 percent net decrease in injuries, while increasing wheelbase by 4.5 inches while maintaining weight showed a 26 percent net decrease in serious injuries.

Agencies’ response:

The agencies have reviewed Mr. Wenzel’s draft report for DOE to which he referred in his comments, but based on NHTSA’s work do not find such a wide range of safety risk for vehicles with the same weight, although we agree there is a range of risk for a given footprint. Wenzel found that for drivers, casualty risk does generally decrease as weight or footprint increases, especially for passenger cars, and that in terms of risk imposed on the drivers of other vehicles, risk increases as light truck weight or footprint increases, but concluded that the variation in the data precluded the possibility of drawing any conclusions. In the 2010 Kahane study presented in the FRIA, NHTSA undertook a similar analysis in which it correlated weight to fatality risk for vehicles of essentially the same footprint. 24 The “decile analysis,” provided as a check on the trend/direction of NHTSA’s regression analysis, shows that societal fatality risk generally increases and rarely decreases for lighter relative to heavier cars of the same footprint. Thus, while Mr. Wenzel was reluctant to draw a conclusion, NHTSA believes that both our research and Mr. Wenzel’s appear to point to the same conclusion. We agree that there is a wide range in casualty risk among cars of the same footprint, but we find that that casualty risk is correlated with weight. The correlation shows that heavier cars have lower overall

societal fatality rates than lighter cars of very similar footprint.

The agencies agree that simulation can be beneficial in certain circumstances. NHTSA cautions, however, that it is difficult for a simulation analysis to capture the full range of variations in crash situations in the way that a statistical regression analysis does. Vehicle crash dynamics are complex, and small changes in initial crash conditions (such as impact angle or closing speed) can have large effects on injury outcome. This condition is a consequence of variations in the deformation mode of individual components ( e.g. , buckling, bending, crushing, material failure, etc.) and how those variations affect the creation and destruction of load paths between the impacting object and the occupant compartment during the crash event. It is therefore difficult to predict and assess structural interactions using computational methods when one does not have a detailed, as-built geometric and material model. Even when a complete model is available, prudent engineering assessments require extensive physical testing to verify crash behavior and safety. Despite all this, the agencies recognize that detailed crash simulations can be useful in estimating the relative structural effects of design changes over a limited range of crash conditions, and will continue to evaluate the appropriate use

of this tool in the future.

Simplified crash simulations can also be valuable tools, but only when employed as part of a comprehensive analytical program. They are especially valuable in

24 Subsection s 2.4 and 3.3 of new report. Deleted: SectionDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

20 evaluating the relative effect and associated confidence intervals of feasible design alternatives. For example, the method employed by Nusholtz et al

. 25 could be used by a vehicle designer to estimate the benefit of incremental changes in mass or wheelbase as well as the tradeoffs that might be made between them once that designer has settled on a preliminary design. A key difference between the research by Nusholtz and the research by Kebschull that Mr. Wenzel cited 26 is in their suggested applications. The former is useful in evaluating proposed alternatives early in the design process – Nusholtz specifically warns that the model provides only “general insights into the overall risk ... and cannot be used to obtain specific response characteristics.” Mr. Wenzel implies the latter can “isolate the effect of specific design changes, such as weight reduction” and thus quantify the fleet-wide effect of substantial vehicle redesigns. Yet while Kebschull reports injury reductions to three significant digits, there is no validation that vehicle structures of the proposed weight and stiffness are even feasible with current technology. Thus, while the agencies agree that computer simulations can be useful tools, we also recognize the value of statistical regression analysis for determining fleet-wide effects, because it inherently incorporates real-world factors in historical safety assessments.

DRI’s analysis shows that lighter vehicles will save lives, and NHTSA reaches the opposite conclusion without disproving DRI’s analysis

The difference between NHTSA’s results and DRI’s results for the relationship between vehicle mass and vehicle safety has been at the crux of this issue for several years. While NHTSA offered some theories in the NPRM as to why DRI might have found a safety benefit for mass reduction, NHTSA’s work since then has enabled it to identify what we believe is the most likely reason for DRI’s findings. The potential near multicollinearity of the variables of curb weight, track width, and wheelbase creates some degree of concern that any regression models with those variables could inaccurately calibrate their effects. However, based on its own experience with statistical analysis, NHTSA believes that the specific two-step regression model used by DRI increases this

concern , because it weakens relationships between curb weight and dependent variables by splitting the effect of curb weight across the two regression steps.

25 Nusholtz, G.S., G. Rabbiolo, and Y. Shi, “Estimation of the Effects of Vehicle Size and Mass on CrashInjury Outcome Through Parameterized Probability Manifolds,” Society of Automotive Engineers (2003),

Document No. 2003-01-0905. Available at http://www.sae.org/technical/papers/2003-01-0905 (last accessed Feb. 15, 2010).

26 Mr. Wenzel cites the report by Kebschull et al [2004, DRI-TR-04-04-02] as an example of what he regards as the effective use of computer crash simulation. NHTSA does not concur that this analysis represents a viable analytical method for evaluating the fleet-wide tradeoffs between vehicle mass and societal safety. The simu lation method employed was not a full finite element representa tion of each major structural component in the vehicles in question. Instead, an Articulated Total Body (ATB) representation was constructed for each of two representative vehicles. In the ATB model, large structural subsystems were represented by a single ellipsoid. Consolidated load-deflection properties of these subsystems and the joints that tie them together were “calibrated” for an ATB vehicle model by requiring that it reproduce the acceleration pulse of a physical NHTSA crash test. NHTSA notes that vehicle simulation models that are calibrated to a single crash test configuration ( e.g. , a longitudinal NCAP test into a rigid wall) are often illequipped to analyze alternative crash scenarios ( e.g. , vehicle-to-vehicle crashes at arbitrary angles and lateral offsets). Deleted: risk

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21 The comments below are in response to NHTSA’s theories in the NPRM about

the source of the differences between NHTSA’ s and DRI’s results. The majority of them are answered more fully in the 2010 Kahane report included in NHTSA’s FRIA, but we respond to them in this document as well for purposes of completeness.

NHTSA and DRI may have reached different conclusions because NHTSA’s study does not distinguish between reductions in size and reductions in weight

like DRI’s

Several commenters (CARB, CBD, EDF, ICCT, NRDC, and UCS) stated that DRI had been able to separate the effect of size and weight in its analysis, and in so doing proved that there was a safety benefit to reducing weight without reducing size. The commenters suggested that if NHTSA properly distinguished between reductions in size and reductions in weight, it would find the same result as DRI.

Agencies’ response:

In the 2010 Kahane analysis presented in the FRIA, NHTSA did attempt to separate the effects of vehicle size and weight by performing regression analyses with footprint (or alternatively track width and wheelbase) and curb weight as separate independent variables. For passenger cars, NHTSA found that the regressions attribute the fatality increase due to downsizing about equally to mass and footprint – that is, the effect of reducing mass alone is about half the effect of reducing mass and reducing footprint. Unlike DRI’s results, NHTSA’s regressions for passenger cars and for lighter LTVs did not find a safety benefit to reducing weight without reducing size; while NHTSA did find a safety benefit for reducing weight in the heaviest LTVs, the magnitude of the benefit as compared to DRI’s was significantly smaller. NHTSA

believes that these differences in results ma y be an artifact of DRI’s two-step regression model, as explained above.

NHTSA and DRI may have reached different conclusions because NHTSA’s study does not include two-door cars like DRI’s

One of NHTSA’s primary theories in the NPRM as to why NHTSA and DRI’s results differed related to DRI’s inclusion in its analysis of 2-door cars. NHTSA had excluded those vehicles from its analysis on the grounds that 2-door cars had a disproportionate crash rate (perhaps due to their inclusion of muscle and sports cars) which appeared likely to skew the regressi on. Several commenters argued that NHTSA should have included 2-door cars in its analysis. DRI and James Adcock stated that 2-door cars should not be excluded because they represent a significant portion of the lightduty fleet, while CARB and ICCT stated that because DRI found safety benefits whether 2-door cars were included or not, NHTSA should include 2-door cars in its analysis. Wenzel also commented that NHTSA should include 2-door cars in subsequent analyses, stating that while his analysis of MY 2000-2004 crash data from 5 states indicates that, in general, 4-door cars tend to have lower fatality risk than 2-door cars, the risk is even lower when he accounts for driver age/gender and crash location. Wenzel suggested thatDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

22 the increased fatality risk in the 2-door car population seemed primarily attributable to the sports cars, and that that was not sufficient grounds to exclude all 2-door cars from NHTSA’s analysis.

Agencies’ response:

The agencies agree that 2-door cars can be included in the analysis, and NHTSA retracts previous statements that DRI’s inclusion of them was incorrect. In its 2010 analysis, NHTSA finds that it makes little difference to the results whether 2-door cars are included, partially included, or excluded from the analysis. Thus, analyses of 2-door and 4-door cars combined, as well as other combinations, have been included in the analysis. That said, no combination of 2-door and 4-door cars resulted in NHTSA’s finding a safety benefit for passenger cars due to mass reduction.

NHTSA and DRI may have reached different conclusions due to different assumptions

DRI commented that the differences found between its study and NHTSA’s may be due to the different assumptions about the linearity of the curb weight effect and control variable for driver age, vehicle age, road conditions, and other factors. NHTSA’s analysis was based on a two-piece linear model for curb weight with two different weight groups (less than 2,950 lbs., and greater than or equal to 2.950 lbs). The DRI analysis assumed a linear model for curb weight with a single weight group. Additionally, DRI stated that NHTSA’s use of eight control variables (rather than three control variables like DRI used) for driver age introduces additional degrees of freedom into the regressions, which it suggested may be correlated with the curb weight, wheelbase, and track width, and/or other control variables. DRI suggested that this may also affect the

results and cause or contribute to the differences in outcomes between NHTSA and DRI.

Agencies’ response:

NHTSA’s FRIA documents that NHTSA analyzed its database using both a single parameter for weight (a linear model) and tw o parameters for weight (a two-piece linear model). In both cases, the logistic regression responded identically, allocating the same way between weight, wheelbase, track width, or footprint. 27 Thus, NHTSA does not

believe that the differences between its resu lts and DRI’s results are due to whether the studies used a single weight group or two weight groups.

The FRIA also documents that NHTSA examined NHTSA’s use of eight control variables for driver age (ages 14-30, 30-50, 50-70, 70+ for males and females separately , versus DRI’s use of three control variables for age (FEMALE = 1 for females, 0 for males, YOUNGDRV = 35-AGE for drivers under 35, 0 for all others, OLDMAN = AGE-50 for males over 50, 0 for all others; OLDWOMAN = AGE-45 for females over 45, 0 for all others) to see if that affected the results. NHTSA ran its analysis using the eight control variables and again using three control variables for age, and obtained

27 Subsection s 2.2 and 2.3 of new report Deleted: SectionDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

23 similar results each time. 28 Thus, NHTSA does not believe that the differences between

its results and DRI’s results are due to the nu mber of control variables used for driver

age.

NHTSA’s and DRI’s conclusions may be similar if confidence intervals are

taken into account

DRI commented that NHTSA has not reported confidence intervals, while DRI has reported them in its studies. Thus, DRI argued, it is not possible to determine whether the confidence intervals overlap and whether the differences between NHTSA’s and DRI’s analyses are statistically significant.

Agencies’ response:

NHTSA has included confidence intervals for the main results of the 2010 Kahane analysis, as shown in Chapter IX of NHTSA’s FRIA. For passenger cars, the NHTSA results are a statistically significant increase in fatalities with a 100 pound reduction while maintaining track width and wheelbase (or footprint); the DRI results are a statistically significant decrease in fatalities with a 100 pound reduction while maintaining track width and wheelbase. The DRI results are thus outside the confidence bounds of the NHTSA results and do not overlap.

NHTSA should include a “best-case” estimate in its study

Several commenters (Center for Auto Safety, NRDC, Public Citizen, Sierra Club

et al. , and Wenzel) urged NHTSA to include a “best-case” estimate in the final rule, showing scenarios in which lives were saved rath er than lost. Public Citizen stated that there would be safety benefits to reducing the weight of the heaviest vehicles while leaving the weight of the lighter vehicles unchanged, and that increasing the number of smaller vehicles would provide safety benefits to pedestrians, bicyclists, and motorcyclists. Sierra Club et al . stated that new materials, smart design, and lighter, more advanced engines can all improve fuel economy while maintaining or increasing vehicle safety. Both Center for Auto Safety and Sierra Club argued that the agency should have presented a “best-case” scenario to balance out the “worst-case” scenario presented in the NPRM, especially if NHTSA itself believed that the worst-case scenario was not inevitable. NRDC requested that NHTSA present both a “best-case” and a “most likely” scenario. Wenzel simply stated that NHTSA did not present a “best-case” scenario, despite DRI’s finding in 2005 that fatalities would be reduced if track width

was held constant.

Agencies’ response:

NHTSA has included an “upper estimate” and a “lower estimate” in the new 2010 Kahane analysis. The lower estimate assumes that mass reduction will be accomplished entirely by material substitution or other techniques that do not perceptibly change a

28 Id.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

24 vehicle’s shape, structural strength, or ride quality. The lower estimate examines specific crash modes and is meant to reflect the increase in fatalities for the specific crash modes

in which a reduction in mass per se in the case vehicle would result in a reduction in safety: namely, collisions with larger vehicles not covered by the regulations ( e.g. , trucks with a GVWR over 10,000 lbs), collisions with partially-movable objects ( e.g. , some trees, poles, parked cars, etc.), and collisions of cars or light LTVs with heavier LTVs – as well as the specific crash modes where a reduction in mass per se in the case vehicle would benefit safety: namely, collisions of heavy LTVs with cars or lighter LTVs.

NHTSA believes that this is the effect of mass per se , i.e. , the effects of reduced mass will generally persist in these crashes regard less of how the mass is reduced. The lower estimate attempts to quantify that scenario, although any such estimate is hypothetical and subject to considerable uncertainty. NH TSA believes that a “most likely” scenario cannot be determined with any certainty, and would depend entirely upon agency assumptions about how manufacturers intend to reduce mass in their vehicles. While we can speculate upon the potential effects of different methods of mass reduction, we cannot predict with certainty what manufacturers will ultimately do.

NHTSA should not include a “wor st-case” estimate in its study

NRDC, Public Citizen and Sierra Club et al. commented that NHTSA should remove the “worst-case scenario” estimate from the rulemaking, generally because it was based on an analysis that evaluated historical vehicles, and future vehicles would be sufficiently different to render the “worst-case scenario” inapplicable.

Agencies’ response:

NHTSA stated in the NPRM that the “worst-case scenario” addressed the effect of a kind of downsizing ( i.e. , mass reduction accompanied by footprint reduction) that was not likely to be a consequence of attribute-based CAFE standards, and that the agency would refine its analysis of such a scenario for the final rule. NHTSA has not used the “worst-case scenario” in the final rule. Instead, we present three scenarios: the first is an estimate based directly on the regression coefficients of weight reduction while maintaining footprint in the statistical analyses of historical data. As discussed above, presenting this scenario is possible because NHTSA attempted to separate the effects of weight and footprint reduction in the new analysis. However, even the new analysis of LTVs produced some coefficients that NHTSA did not consider entirely plausible. NHTSA also presents an “upper estimate” in which those coefficients for the LTVs were adjusted based on additional analyses and expert opinion as a safety agency and a “lower estimate,” which estimates the effect if mass reduction is accomplished entirely by safety-conscious technologies such as material substitution.

3. How has NHTSA refined its analysis for purposes of estimating the potential safety effects of this final rule?

During the past months, NHTSA has extensively reviewed the literature on vehicle mass, size, and fatality risk. NHTSA now agrees with DRI and other commenters Deleted: was ableDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

25 that it is essential to analyze the effect of mass independently from the effects of sizeparameters such as wheelbase, track width, or footprint – and that the NPRM’s “worstcase” scenario based on downsizing (in which weight, wheelbase, and track width could all be changed) is not useful for that purpose. The agency should instead provide estimates that better reflect the more likely ef fect of the regulation - estimating the effect of mass reduction that maintains footprint.

Yet it is more difficult to analyze multiple, independent parameters than a single parameter ( e.g. , curb weight), because there is a potential concern that the near multicollinearity of the parameters – the strong, natural and historical correlation of mass

and size – can lead to inaccurate statistical estimates of their effects. 29 NHTSA has performed new statistical analyses of its hi storical database of passenger cars, light trucks, and vans (LTVs) from its 2003 report (now including also 2-door cars), assessing relationships between fatality risk, mass, and footprint. They are described in

S ubs ections 2.2 (cars) and 3.2 (LTVs) of the 2010 Kahane report presented in Chapter IX of the FRIA. While the potential concerns associated with near multicollinearity are inherent in regression analyses with multiple size/mass parameters, NHTSA believes that the analysis approach in the 2010 Kahane report, namely a single-step regression analysis, generally reduces those concerns 30 and models the trends in the historical data. The results differ substantially from DRI’s, based on a two-step regression analysis.

S ubs ections 2.3 and 2.4 of the 2010 Kahane report attempt to account for the differences primarily by applying selected techniques from DRI’s analyses to NHTSA’s database.

The statistical analyses – logistic regressions – of trends in MYs 1991-1999 vehicles generate one set of estimates of the possible effects of reducing mass by 100 pounds while maintaining footprint. While these effects might conceivably carry over to future mass reductions, there are two reasons that future safety effects of mass reduction could differ from projections from historical data:

• The statistical analyses are “cross-sectional” analyses that estimate the increase in fatality rates for vehicles weighing n-100 pounds relative to vehicles weighing n pounds, across the spectrum of vehicles on the road, from the lightest to the heaviest. They do not directly compare the fatality rates for a specific make and model before and after a 100–pound reduction from that model. Instead, they use the differences across makes and models as a surrogate for the effects of actual reductions within a specific model; those cross-sectional differences could include trends that are statistically, but not causally related to mass.

29 Greene, W. H. (1993). Econometric Analysis , Second Edition. New York: Macmillan Publishing Company, pp. 266-268; Allison, P.D. (1999), Logistic Regression Using the SAS System . Cary, NC: SAS Institute Inc., pp. 48-51. The report shows variance inflation factor (VIF) scores in the 5-7 range for curb weight, wheelbase, and track width (or, alternatively, curb weight and footprint) in NHTSA’s database, exceeding the 2.5 level where near multicollinearity begins to become a concern in logistic regression analyses.

30 NHTSA believes that, given the near multicollinearity of the independent variables, the two-step regression augments the possibility of estimating inaccurate coefficients for curb weight, because it weakens relationships between curb weight and dependent variables by splitting the effect of curb weight across the two regression steps as discussed further in Subsection 2.3 of NHTSA’s report. Deleted: minimizes

Deleted: hazards

Deleted: NHTSA believes that the twostep regression is more hazardous because it weakens relationships between curb weight and dependent variables by splitting the effect of curb weight across the two regression steps, as discussed

further below.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

26 • The manner in which mass changed across MY 1991-1999 vehicles might not be consistent with future mass reductions, due to the availability of newer materials and design methods.

Therefore, S ubs ections 2.5 and 3.4 of the 2010 Kahane report supplement those estimates with one or more scenarios in which some of the logistic regression coefficients are replaced by numbers based on additional analyses and NHTSA’s judgment of the likely

effect of mass per se (the ability to transfer momentum to other vehicles or objects in acollision) and of what trends in the historical data could be avoided by current massreduction technologies such as materials substitution. The various scenarios may be viewed as a plausible range of point estimates for the effects of mass reduction while maintaining footprint, but they should not be construed as upper and lower bounds. Furthermore, being point estimates, they are themselves subject to uncertainties, such as, for example, the sampling errors associated with statistical analyses.

The principal findings and conclusions of the 2010 Kahane report are as follows:

Passenger cars : This database with the one-step regression method of the 2003 Kahane report estimates an increase of 700-800 fatalities when curb weight is reduced by 100 pounds and footprint is reduced by 0.65 square feet (the historic average footprint reduction per 100-pound mass reduction in cars). The regression attributes the fatality increase about equally to curb weight and to footprint . The results are approximately the same whether 2-door cars are fully included or partially included in the analysis or whether only 4-door cars are included (as in the 2003 report). Regressions by curb weight, track width and wheelbase produce find ings quite similar to the regressions by curb weight and footprint, but the results with the single “size” variable, footprint, rather than the two variables, track width and wheelbase vary even less with the inclusion or

exclusion of 2-door cars.

In S ubs ection 2.3 of the new report, a two-step regression method that resembles (without exactly replicating) the approach by DRI, when applied to the same (NHTSA’s) crash and registration data , estimates a large benefit when mass is reduced, offset by even larger fatality increases when track width and wheelbase (or footprint) are reduced. NHTSA believes that the benefit estimated by this method is inaccurate, due to the potential concerns with the near multicollinea rity of the parameters (curb weight, track width, and wheelbase) 31 even though the analysis is theoretically unbiased 32 . Almost any analysis incorporating those parameters has a po ssibility of inaccurate coefficients due to near multicollinearity; however, based on our own experience with other regression analyses of crash data, NHTSA believes a DRI-type two-step method augments the

31 As evidenced by VIF scores in the 5-7 range, exceeding the 2.5 level where near multicollinearity begins to become a concern in logistic regression analyses.

32 S ubs ection 2.3 of the 2010 Kahane report attempts to explain why the two-step method, when applied to NHTSA’s 2003 database, produces results a lot like DRI’s, but it does not claim that DRI obtained itsresults from its own database for exactly those reasons. NHTSA did not analyze DRI’s database. The twostep method is “theoretically unbiased” in the sense that it seeks to estimate the same parameters as the one-step analysis.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

27 possibility of estimating inaccurate coefficients for curb weight, because it weakens relationships between curb weight and dependent variables by splitting the effect of curb weight across the two regression steps.

In S ubs ection 2.4 of the new report, as a check on the results from the regression methods, NHTSA also performed what we refe r to as “decile” analyses: simpler, tabular data analysis that compares fatality rates of cars of different mass but similar footprint. Decile analysis is not a precise tool because it does not control for confounding factors such as driver age/gender or the specific type of car, but it may be helpful in identifying the general directional trend in the data when footprint is held constant and curb weight varies. The decile analyses show that fatality risk in MY 1991-1999 cars generally increased and rarely decreased for lighter relative to heavier cars of the same footprint

. They suggest that the historical, cross-sectional trend was generally in the lighter ↔ more fatalities direction and not in the opposite direction, as might be suggested by the regression coefficients from the method that resembles DRI’s approach.

The regression coefficients from NHTSA’s one-step method suggest that mass and footprint each accounted for about half the fatality increase associated with downsizing in a cross-sectional analysis of 1991-1999 cars. They estimate the historical

difference in societal fatality rates ( i.e. , including fatalities to occupants of all the vehicles involved in the collisions, plus any pedestrians) of cars of different curb weights but the same footprint. They may be considered an “upper-estimate scenario” of the effect of future mass reduction – if it were accomplished in a manner that resembled the historical

cross-sectional trend – i.e. , without any particular regard for safety (other than not to reduce footprint).

However, NHTSA believes that future vehi cle design is likely to take advantage of safety-conscious technologies such as ma terials substitution that can reduce mass without perceptibly changing a car’s shape or ride and maintain its structural strength. This could avoid much of the risk associated with lighter and smaller vehicles in the historical analyses, especially the historical trend toward higher crash-involvement rates for lighter and smaller vehicles. 33 It could thereby shrink the added risk close to just the

effects of mass per se (the ability to transfer momentum to other vehicles or objects in a collision). S ubs ection 2.5 of the 2010 Kahane report attempts to quantify a “lowerestimate scenario” for the potential effect of mass reduction achieved by safety-conscious technologies; the estimated effects are substan tially smaller than in the upper-estimate scenario based directly on the regression results.

We note, again, that the preceding paragraph is conditional. Nothing in the CAFE standard requires manufacturers to use material substitution or, more generally, take a

33
This is discussed in greater depth in Subsections 2.1 and 2.5 of the 2010 Kahane report. The historic trend toward higher crash-involvement rates for lighter and smaller vehicles is documented in IIHS Advisory No. 5, July 1988, http://www.iihs.org/research/advisories/iihs_advisory_5.pdf; IIHS News Release, February 24, 1998, http://www.iihs.org/news/1998/iihs_news_022498.pdf; Auto Insurance Loss Facts, September 2009, http://www.iihs.org/research/hldi/fact_sheets/CollisionLoss_0909.pdf. Deleted: IIHS Advisory No. 5, July 1988, http://www.iihs.org/research/advisories/ii hs_advisory_5.pdf; IIHS News Release, February 24, 1998, http://www.iihs.org/news/1998/iihs_news _022498.pdf; Auto Insurance Loss Facts, September 2009, http://www.iihs.org/research/hldi/fact_sh eets/CollisionLoss_0909.pd f

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28 safety-conscious approach to mass reduction. 34 Federal Motor Vehicle Safety Standards include performance tests that verify histor ical improvements in structural strength and crashworthiness, but few FMVSS provide test information that sheds light about how a vehicle rides or otherwise helps explain the trend toward higher crash-involvement rates for lighter and smaller vehicles. It is possible that using material substitution and other current mass reduction methods could avoid the historical trend in this area, but that

remains to be studied as manufacturers introduce more of these vehicles into the on-road fleet in coming years. A detailed discussion of methods currently used for reducing the mass of passenger cars and light trucks is included in Chapter 3 of the Technical Support

Document.

LTVs : The principal difference between LTVs and passenger cars is that mass reduction in the heavier LTVs is estimated to have significant societal benefits, in that it reduces the fatality risk for the occupants of cars and light LTVs that collide with the heavier LTVs. By contrast, footprint (size) reduction in LTVs has a harmful effect (for the LTVs’ own occupants), as in cars. The regression method of the 2003 Kahane report applied to the database of that report estimates a societal increase of 231 fatalities when curb weight is reduced by 100 pounds and footprint is reduced by 0.975 square feet (the historic average footprint reduction per 100-pound mass reduction in LTVs). But the regressions attribute

an overall reduction of 266 fatalities to the 100-pound mass reduction and an increase of 497 fatalities to the .975-square-foot footprint reduction. The regression results constitute one of the scenarios for the possible societal effects of future mass reduction in LTVs.

However, NHTSA cautions that some of the regression coefficients, even by NHTSA’s preferred method, might not accurately model the historical trend in the data, possibly due to near multicollinearity of curb weight and footprint or because of the interaction of both of these variables with LTV type. 35 Based on supplementary analyses

and discussion in S ubs ections 3.3 and 3.4, the new report defines an additional upperestimate scenario that NHTSA believes may more accurately reflect the historical trend in the data and a lower-estimate scenario that may come closer to the effects of mass per se

. All three scenarios, however, attribute a so cietal fatality reduction to mass reduction in

the heavier LTVs.

Overall effects of mass reduction while maintaining footprint in cars and LTVs : The immediate purpose of the new report’s analyses of relationships between fatality risk, mass, and footprint is to develop the four pa rameters that the Volpe model needs in order to predict the safety effects, if any, of the modeled mass reductions in MYs 2012-2016

cars and LTVs over the lifetime of those vehicles. The four numbers are the overall percentage increases or decreases, per 100 -pound mass reduction while holding footprint constant, in crash fatalities involving: (1) cars < 2,950 pounds (which was the median

34 Footprint-based standards do not specify how or where to remove mass while maintaining footprint, nor do they categorically forbid footprint reductions, even if they discourage them.

35 For example, mid-size SUVs of the 1990s typically had high mass relative to their short wheelbase and footprint (and exceptionally high rates of fatal rollovers); minivans typically have low mass relative to their footprint (and low fatality rates); heavy-duty pickup trucks used extensively for work tend to have more mass, for the same footprint, as basic full-sized pickup trucks that are more often used for personal transportation.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

29 curb weight of cars in MY 1991-1999), (2) cars ≥ 2,950 pounds, (3) LTVs < 3,870 pounds (which was the median curb weight of LTVs in those model years), and (4) LTVs

≥ 3,870 pounds. Here are the percentage effects for each of the three alternative scenarios, again, the “upper-estimate scenario” and the “lower-estimate scenario” have been developed based on NHTSA’s expert opinion as a vehicle safety agency:

Fatality Increase per 100-Pound Reduction (%) 36

Actual Regression

Result Scenario NHTSA ExpertOpinion UpperEstimate

Scenario 37 NHTSA ExpertOpinion LowerEstimate Scenario

Cars < 2,950 pounds 2.21 2.21 1.02

Cars > 2,950 pounds 0.90 0.90 0.44

LTVs < 3,870 pounds 0.17 0.55 0.41

LTVs > 3,870 pounds -1.90 -0.62 -0.73

In all three scenarios, the estimated effects of a 100-pound mass reduction while maintaining footprint are an increase in fatalities in cars < 2,950 pounds, substantially

smaller increases in cars ≥ 2,950 pounds and LTVs < 3,870 pounds, and a societal benefit

for LTVs ≥ 3,870 pounds (because it reduces fatality risk to occupants of cars and lighter LTVs they collide with). These are the estim ated effects of reducing each vehicle by exactly 100 pounds. However, the actual mass reduction will vary by make, model, and year. The aggregate effect on fatalities can only be estimated by attempting to forecast, as NHTSA has using inputs to the Volpe model, the mass reductions by make and model. It should be noted, however, that a 100-pound reduction would be 5 percent of the mass of a 2000-pound car but only 2 percent of a 5000-pound LTV. Thus, a forecast that mass will decrease by an equal or greater percentage in the heavier vehicles than in the lightest cars would be proportionately more influenced by the benefit for mass reduction in the heavy LTVs than by the fatality increases in the other groups; it is likely to result in an estimated net benefit under one or more of the scenarios. It should also be noted, again,

36 Reducing mass by 100 pounds in these vehicles is estimated to have the listed percentage effect on fatalities in crashes involving these vehicles. For example, if these vehicles are involved in crashes that result in 10,000 fatalities, 2.21 means that if mass is reduced by 100 pounds, fatalities will increase to 10,221 and -0.73 means fatalities will decrease to 9,927. In the scenario based on actual regression results, the 1.96-sigma sampling errors in the above estimates are ±0.91 percentage points for cars < 2,950 pounds

and also for cars ≥ 2,950 pounds, ±0.82 percentage points for LTVs < 3,870 pounds, and ±1.18 percentage points for LTVs ≥ 3,870 pounds. In other words, the fatality increase in the cars < 2,950 pounds and the societal fatality reduction attributed to mass reduction in the LTVs ≥ 3,870 pounds are statistically significant. The sampling errors associated with the scenario based on actual regression results perhaps also indicate the general level of statistical noise in the other two scenarios.

37 For passenger cars, the upper-estimate scenario is the actual-regression-result scenario.DRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

30 that the three scenarios are point estimates and are subject to uncertainties, such as the sampling errors associated with the regression results. In the scenario based on actual regression results, the 1.96-sigma sampling errors in the above estimates are + 0.91 percentage points for cars < 2,950 pounds and also for cars > 2,950 pounds, + 0.82 percentage points for LTVs < 3,870 pounds, and + 1.18 percentage points for LTVs > 3,870 pounds. In other words, the fatality increase in the cars < 2,950 pounds and the societal fatality reduction attributed to mass reduction in the LTVs > 3,870 pounds are statistically significant. The sampling errors associated with the scenario based on actual regression results perhaps also indicate the gene ral level of statistical noise in the other

two scenarios.

4. What are the estimated safety effects of this final rule?

The table below shows the estimated safety effects of the modeled reduction in vehicle mass provided in the NPRM and in this final rule in order to meet the MYs 2012- 2016 standards, based on the analysis described briefly above and in much more detail in Chapter IX of the FRIA. These are combined results for passenger cars and light trucks. A positive number is an estimated increase in fatalities and a negative number (shown in parentheses) is an estimated reduction in fatalities over the lifetime of the model year vehicles compared to the MY 2011 baseline fleet.

MY

2012 MY

2013 MY

2014 MY

2015 MY

2016

NPRM “Worst Case” 34 54 194 313 493

NHTSA Expert Opinion Final Rule Upper Estimate 9 14 26 24 22

NHTSA Expert Opinion Final Rule

Lower Estimate 2 4 (17) (53) (80)

Actual Regression

Result Scenario 0 2 (94) (206) (301)

NHTSA emphasizes that the table above is based on the NHTSA’s assumptions about how manufacturers might choose to reduce the mass of their vehicles in response to the final rule, which are very similar to EPA’s assumptions. In general, as discussed above, the agencies assume that mass will be reduced by as much as 10 percent in the heaviest LTVs but only by as much as 5 percent in other vehicles and that substantial mass reductions will take place only in the year that models are redesigned. The actual mass reduction that is likely to occur in response to the standards will of course vary by make and model, depending on each manufacturer’s particular approach, with likely more opportunity for the largest LTVs that still use separate frame construction.

The “upper estimate” presented above, as discussed in the FRIA, assumes only that manufacturers will reduce vehicle mass without reducing footprint. Thus, under such a scenario, safety effects could be somewhat adverse if, for example, manufacturersDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

31 chose to reduce crush space associated with vehicle overhang as a way of reducing mass without changing footprint. The “lower estimate,” in turn, is based on the assumption that manufacturers will reduce vehicle mass solely through methods like material substitution, which (under these assumptions) fully maintain not only footprint but also all structural integrity, and other aspects of vehicle safety. Under these scenarios, safety effects could be worse if mass reduction was not undertaken thoughtfully to maintain existing safety levels, but could also be better if it was undertaken with a thorough and extensive vehicle redesign to maximize both mass reduction and safety.

And finally, while NHTSA does not believe that the “worst-case” scenario presented in the NPRM is likely to occur during the MYs 2012-2016 timeframe, we cannot guarantee that manufacturers will ne ver choose to reduce vehicle footprint, particularly if market forces lead to increased sales of small vehicles in response to sharp increases in the price of petroleum, though this situation would not be in direct response to the CAFE/GHG standards. Thus, we cannot completely reject the worst-case scenario for all vehicles, although we can and do recognize that the footprint-based standards will significantly limit the likelihood of its occurrence within the context of this rulemaking.

In summary, the agencies recognize the balancing inherent in achieving higher levels of fuel economy and lower levels of CO 2 emissions through reduction of vehicle mass. Based on the 2010 Kahane analysis that attempts to separate the effects of mass reductions and footprint reductions, and to account better for the possibility that mass reduction will be accomplished entirely through methods that preserves structural strength and vehicle safety, the agencies now believe that the likely deleterious safety effects of the MYs 2012-2016 standards may be much lower than originally estimated. They may be close to zero, or possibly beneficial if mass reduction is carefully undertaken in the future and if the mass reduction in the heavier LTVs is greater (in absolute terms) than in passenger cars. In light of these findings, we believe that the balancing is reasonable.

5. How do the agencies plan to address this issue going forward?

NHTSA and EPA believe that it is important for the agencies to conduct further study and research into the interaction of mass, size and safety to assist future rulemakings. The agencies intend to begin working collaboratively and to explore with DOE, CARB, and perhaps other stakeholders an interagency/ intergovernmental working group to evaluate all aspects of mass, size and safety. It would also be the goal of this team to coordinate government supported stud ies and independent research, to the extent possible, to help ensure the work is complementary to previous and ongoing research and to guide further research in this area. DOE’s EERE office has long funded extensive research into component advanced vehicle materials and vehicle mass reduction. Other agencies may have additional expertise that will be helpful in establishing a coordinated work plan. The agencies are interested in looking at the weight-safety relationship in a more holistic (complete vehicle) way, and thanks to this CAFE rulemaking NHTSA has begun to bring together parts of the agency— crashworthiness, and crash avoidance rulemaking offices and the agency’s Research & Development office—in an Deleted: is ableDRAFT – DELIBERATIVE – PRIVILEGED AND CONFIDENTIAL

32 interdisciplinary way to better leverage the expertise of the agency. Extending this effort to other agencies will help to ensure that all aspects of the weight-safety relationship are considered completely and carefully with our fu ture research. The agencies also intend to carefully consider comments received in response to the NPRM in developing plans for future studies and research and to solicit input from stakeholders.

The agencies also plan to watch for safe ty effects as the U.S. light-duty vehicle fleet evolves in response both to the CAFE/GHG standards and to consumer preferences over the next several years. Additionally, as new and advanced materials and component smart designs are developed and commerciali zed, and as manufacturers implement them in more vehicles, it will be useful for the agencies to learn more about them and to try to track these vehicles in the fleet to understand the relationship between vehicle design and injury/fatality data. Specifically, the agencies intend to follow up with study and research of the following: First, NHTSA is in the process of contracting with an independent institution to

review the statistical methods that NHTSA and DRI have used to analyze historical data related to mass, size and safety, and to provide recommendation on whether the existing methods or other methods should be used for future statistical analysis of historical data. This study will include a consideration of potential near multicollinearity in the historical data and how best to address it in a regression analysis. This study is being initiated because, in response to the NPRM, NHTSA received a number of comments related to the methodology NHTSA used for the NPRM to determine the relationship between mass and safety, as discussed in detail above.

Second, NHTSA and EPA, in consultation with DOE, intend to begin updating the MYs 1991-1999 database on which the safety analyses in the NPRM and final rule

are based with newer vehicle data in the next se veral months. This task will take at least a year to complete. This study is being initiated in response to the NPRM comments related to the use of data from MYs 1991-1999 in the NHTSA analysis, as discussed in

detail above.

Third, in order to assess if the design of recent model year vehicles that incorporate various mass reduction methods affect the relationships among vehicle mass, size and safety, NHTSA and EPA intend to conduct collaborative statistical analysis, beginning in the next several months. The agencies intend to work with DOE to identify vehicles that are using material substitution and smart design. After these vehicles are identified, the agencies intend to assess if there are sufficient data for statistical analysis. If there are sufficient data, statistical analysis would be conducted to compare the relationship among mass, size and safety of these smart design vehicles to vehicles of similar size and mass with more traditional designs. This study is being initiated because, in response to the NPRM, NHTSA received comments related to the use of data from MYs 1991-1999 in the NHTSA analysis that did not include new designs that might change the relationship among mass, size and safety, as discussed in detail above.

NHTSA may initiate a two-year study of the safety of the fleet through an analysis of the trends in structural stiffness and whether any trends identified impact Deleted: ¶

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33 occupant injury response in crashes. Vehicle manufacturers may employ stiffer light weight materials to limit occupant compartment intrusion while controlling for mass that may expose the occupants to higher accelerations resulting in a greater chance of injury in real-world crashes. This study would provide information that would increase the understanding of the effects on safety of newer vehicle designs.

In addition, NHTSA and EPA, possibly in collaboration with DOE, may conduct a longer-term computer modeling-based design and analysis study to help determine the maximum potential for mass reduction in the MYs 2017-2021 timeframe, through direct material substitution and smart design while meeting safety regulations and guidelines, and maintaining vehicle size and functionality. This study may build upon prior research completed on vehicle mass reduction. This study would further explore the comprehensive vehicle effects, including dissimilar material joining technologies, manufacturer feasibility of both supplier and OEM, tooling costs, and crash simulation and perhaps eventual crash testing.