***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 1 

## Chapter 9. **Safety Impacts**  **9.1 Summary of Supporting HD Vehicle Safety Research**  NHTSA and EPA considered the potential safety i mpact of technologies that improve HD vehicle fuel efficiency

and GHG emissions as part of the assessment of regulatory alternatives. The safet y assessment of the technologies in this proposal was informed by two NAS reports, an anal ys is of safety

effects of HD pickups and vans using estimates from the DOT report on the effect of mass reduction and vehicle size on safety, and agency- sponsored safet y testing and research. A summary

of the literature and work c onsidered b y the agencies follows. 

### 9.2 **National Academy of Sciences HD Phase 1 and Phase 2 Reports** As required b y E IS A , the National Research Council has conducted two studies of the technologies and approaches for reducing the fuel consumption of medium - an d heav y - dut y vehicles. The first was documented in a report issued in 2010, “Technologies and Approaches to Reducing the Fuel Consumption of Medium - and Heav y - Duty Vehicles’’ (“NAS Report”). A The second was documented in a report issued in 2014, “Reducin g the Fuel Consumption and Greenhouse Gas Emissions of Medium - and Heavy - Duty Vehicles, Phase Two - First Report” (“NAS HD Phase 2 First Report”). B While the reports primarily focused on reducing vehicle fuel consumption and emissions through technology app lication, and examined potential regulatory

frameworks, both reports additionally contain findings and recommendations on safet y. In developing this proposal, the agencies carefull y considered both of the reports’ findings related to safety . Some of the reports’ key findings related to safety follow. NAS commented that idle reduction strategies can be sophisticated to provide for the safet y of the driver in hot and cold weather. The agencies considered this comment in our approach for idle reduction technologies (e.g., APUs, diesel fired heaters, and battery powered units with automatic engine shutoff (AES)) and allow override provisions, as discussed in Preamble Section III. Override of the automatic engine shutoff (AES) feature is allowed if the extern al ambient temperature reaches a level below which or above which the cabin temperature cannot be maintained within reasonable heat or cold exposure threshold limit values for the health and safet y of the operator (not merel y comfort).

A Committee to Assess Fuel Economy Technologies for Medium - and Heavy - Duty Vehicles; National Research Council; Transportation Research Board (2010). “ Technologies and Approaches to Reducing the Fuel Consumption of Medium - and Heavy - Duty Vehicles. ” Washingto n, D.C., The National Academies Press. Available electronically from the National Academy Press Website at http:// www.nap.edu/catalog/12845/technologies - and - approaches - to reducing - the - fuel - consum ption - of - medium -- and - heavy - duty - vehicles (last accessed June 4, 2015 ). B Transportation Research Board 2014. “Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium - and Heavy - Duty Vehicles, Phase Two.” Washington, D.C., The National Academies Press. Available electronically from the National Academy Press Website http://www.nap.edu/catalog/18736/reducing - the - fuel consumption - and - greenhouse - gas - emissions - of - me dium -- and - heavy - duty - vehicles - phase - two (last accessed June 4, 2015 ).***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 2 NAS commented extens ively on the recent emergence of natural gas (NG) as a viable technology

option for commercial vehicles, but alluded to the existence of uncertainties regarding its safety . The committee found that while the public crash databases do not contain informati on on vehicle fuel ty pe, the existing information indicates that the crash - related safet y risk for NG storage on vehicles does not appear to be appreciabl y different from diesel fuel risks. The committee also found that while there are two existing SAE - re commended practice standards for NG - powered HD vehicles, the industry could benefit from best practice directives to minimize crash risks for NG fuel tanks, such as on shielding to prevent punctures during crashes. As a final point, NAS stated that manufa cturers and operators have a great incentive to prevent possible NG leakage from a vehicle fuel sy stem because it would be a significant safet y concern and reduce vehicle range. No recommendations were made for additional Federal safety regulations for th ese vehicles. In response, the agencies have reviewed and discuss the existing NG vehicle standards and best practices cited b y NAS in Section XI . In the NAS Committee’s Phase 1 report , the Committee commented that aerody namic fairings detaching from truc ks on the road was a potential safet y issue. However, the Phase 2 interim report stated that “Anecdotal information gained during the observations of on - road trailers indicates a few skirts badly damaged or missing from one side. The skirt manufacturers report no safet y concerns (such as side skirts falling off) and little maintenance needed.” The NAS report also identified the link between tire inflation and condition and vehicle stopping distance and handling, which impacts overall safety . The committ ee found that tire pressure monitoring s ys tems and automatic tire inflation sy stems are being adopted by fleets at an increasing rate. However, the committee noted that there are no standards for performance, display , and s ys tem validation. The committee recommended that NHTSA issue a white paper on the minimum performance of tire pressure s ys tems from a safet y perspective. The agencies considered the safety findings in both NAS reports in developing this proposal and conducted additional research on safety to further examine information and findings of the reports. 

### 9.3 **DOT CAFE Model HD Pickup and Van Safety Analysis** This analy sis considered the potential effects on crash safety of the technologies manufacturers may

apply to their HD pickups and vans to m eet each of the regulatory alternatives evaluated. NHTSA research has shown that vehicle mass reduction affects overall societal fatalities associated with crashes and, most relevant to this proposal, that mass reduction in heavier light - and medium - duty vehicles has an overall beneficial effect on societal fatalities. Reducing the mass of a heavier vehicle involved in a crash with another vehicle(s) makes it less likely that there will be fatalities among the occupants of the other vehicles. Inadditio n to the effects of mass reduction, the anal ys is anticipates that the proposed standards, by reducing the cost of driving HD pickups and vans, would lead to increased travel b y these vehicles and, therefore, more crashes involving these vehicles. The Meth od A analy sis considers overall impacts from both of these factors, using a methodology similar to NHTSA’s anal ys es for the MYs 2017

– 2025 CAFE and GHG emission standards.***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 3 The Method A analy sis includes estimates of the extent to which HD pickups and vans produced during MYs 2014 - 2030 may be involved in fatal crashes, considering the mass, survival, and mileage accumulation of these vehicles, taking into account changes in mass and mileage accumulation under each regulatory alternative. These calculations make use of the same coefficients applied to light trucks in the MYs 2017 - 2025 CAFE rulemaking anal ys is. As discussed above, vehicle miles traveled may increase due to the fuel economy rebound effect, resulting from improvements in vehicle fuel efficienc y and cost of fuel, as well as the assumed future growth in average vehicle use. Increases in total lifetime mileage increase exposure to vehicle crashes, including those that result in fatalities. Consequently , the modeling s ys tem computes total fataliti es attributed to vehicle use for vehicles of a given model year based on safet y class and weight threshold. These calculations also include a term that accounts for the fact that vehicles involved in future crashes will be certified to more stringent safe ty standards than those involved with past crashes upon which the base rates of involvement in fatal crashes were estimated. Since the use of mass reducing technology is present within the model, safety impacts may

also be observed whenever a vehicle’s ba se weight decreases. Thus, in addition to computing total fatalities related to vehicle use, the modeling s ys tem also estimates changes in fatalities due to reduction in a vehicle’s curb weight. The total fatalities attributed to vehicle use and vehicle weight change for vehicles of a given model ye ar are then summed. Lastl y, total fatalities occurring within the industry in a given model ye ar are accumulated across all vehicles. In addition to using inputs to estimate the future involvement of modeled vehicles in crashes involving fatalities, the model also applies inputs defining other accident - related externalities estimated on a dollar per mile basis. For vehicles above 4,594 pounds

—i.e., the majority of the HD pickup and van fleet

— mass reduction is estimated to reduce the net incidence of highway fatalities by 0.34 percent per 100 pounds of removed curb weight. For the few HD pickups and vans below 4,594 pounds, mass reduction is estimated to increase the net incidence of highway fatalities by 0.52 percent per 100 pounds. Because there are man y more HD pickups and vans above 4,594 pounds than below 4,594 pounds, the overall effect of mass reduction in the segment is estimated to reduce the incidence of highway

fatalities. The estimated increase in vehicle miles traveled due to the fuel econom y rebound effect is estimated to increase exposure to vehicle crashes and offset these reductions. 

### 9.4 **Volpe Research on MD/HD Fuel Efficiency Technologies** The 2010 NAS Report recommended that NHTSA perform a thorough safety analysis to identify and evaluate potential safety issues with fuel efficiency - improving technologies. The Department of Transportation Volpe Center’s 2015 report titled “Review and Analy sis of Potential Safety

Impacts of and Regulatory Barriers to Fuel Efficiency Technologies and Alternative Fuels in Medium - and Heav y - Dut y Vehicles” C summarizes research and anal ys is findings on potential safety issues associated with both the diverse alternative fuels (natural gas -

C Brecher, A., Epstein, A. K., & Breck, A. (2015, June). “ Review and analysis of potential safety impacts of and regulatory barriers to fuel efficiency technologies and alternative fuels in medium - and heavy - duty vehicles. ” (Report No. DOT HS 812 159). Washington, DC: National Highway Traffic Safety Administration.***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 4 CNG and LNG, propane, bio diesel, and power train electrification), and the specific FE technologies recentl y adopted by the MD/HDV fleets. These include Intelligent Transportation Sy stems (ITS) and telematics, speed limiters, idle reduction devices, tire technologies (single wide tires, and tire pressure monitoring s ys tems - TPMS and Automated Tire Inflation S ys tems ATI S), aerody

namic components, vehicle light - weighting materials, and Long Combination Vehicles (LCVs). Chapter 1 provides an overview of the study ’s rationale, backgro und, and key objective, namely , to identify

the technical and operational/behavioral safet y benefits and disbenefits of MD/HDVs equipped with FE technologies and using emerging alternative fuels (AFs). Recent MD/HDV national fleet crash safet y statistical averages are also provided for context, although no information exists in crash reports relating to specific vehicle FE technologies and fuels. (NHTSA/FARS and FMCSA/CSA databases do not include detailed information on vehicle fuel econom y technologies, since the state crash report forms are not coded down to an individual fuel econom y technology level). Chapters 2 and 3 are organized by clusters of functionally - related FE technologies for vehicles and trailers (e.g., tire sy stems, ITS, light - weighting materials, and aerodynamic s ys tems) and alternative fuels, which are described and their respective assoc iated potential safet y issues are discussed. Chapter 2 summarizes the findings from a comprehensive review of available technical and trade literature and Internet sources regarding the benefits, potential safety hazards, and the applicable safety regulat ions and standards for deplo yed FE technologies and alternative fuels. Chapter 2 safet y - relevant fuel - specific findings include:

• Both CNG - and LNG - powered vehicles present potential hazards, and call for well known engineering and process controls to assure safe operability and crashworthiness. However, based on the reported incident rates of NGVs and the experiences of adopting fleets, it appears that NGVs can be operated at least as safel y as diesel MD/HDVs.

• There are no safet y contraindications to the large scale fleet adoption of CNG or LNG fueled heav y duty trucks and buses, and there is ample experience with the safe operation of large public transit fleets. Voluntary industry standards and best practices suffice for safety assurance, though impr oved training of CMV operators and maintenance staff in natural gas safety of equipment and operating procedures is needed.

• Observing CNG and LNG fuel s ys tem and maintenance facility standards, coupled with sound design, manufacture, and inspection of nat ural gas storage tanks will further reduce the potential for leaks, tank ruptures, fires, and explosions.

• Biodiesel blends used as drop - in fuels have presented some operational safety concerns dependent on blending fraction, such as material compatibility , bio - fouling sludge accumulation, or cold - weather gelling. However, best practices for biodiesel***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 5 storage, and improved gaskets and seals that are biodiesel resistant, combined with regular maintenance and leak inspection schedules for the fuel lines and components enable the safe use of biodiesel in newer MD/HDVs

• Propane (LPG, or autogas) presents well - known hazards including ignition (due to leaks or crash) that are preventable b y using Overfill Prevention Devices (OPDs), which supplement the automatic stop - fill sy stem on the fueling station side, and pressure release devices (PRDs). Established best practices and safety codes (e.g., NFPA) have proven that propane fueled MD/HDVs can be as operationally safe as the conventionall y - fueled counterparts.

• As the market penetration of hy brid and electric drivetrain accelerates, and as the capacity and reliability

of lithium ion batteries used in Rechargeable Energy Storage Sy stems (RESS) improve, associated potential safety hazards (e.g., electrocution from stranded energy , thermal runaway leading to battery

fire) have become well understood, preventable, and manageable. Existing and emerging industry technical and safet y voluntary standards, applicable NHTSA regulations and guidance, and the growing experi ence with the operation of h ybrid and electric MD/HDVs will enable the safe operation and large - scale adoption of safer and more efficient power - train electrification technologies. The safet y findings from literature review pertaining to the specific FE technologies implemented to date in the MD/HDV fleet include:

• Telematics

—integrating on - board sensors, video, and audio alerts for MD/HDV drivers

— offer potential improvements in both driver safety performance and fuel efficiency . Both camera and non - camer a based telematics setups are currently integrated with available crash avoidance s ys tems (such as ESC, RSC, LDWS, etc.) and appear to be well accepted b y MD/HDV fleet drivers.

• Both experience abroad and the cited US studies of trucks equipped with active speed limiters indicated a safety benefit, as measured b y up to 50 percent reduced crash rates, in addition to fuel savings and other benefits, with good CMV driver acceptance. An y negative aspects were small and avoidable if all the speed limitati on devices were set to the same speed, so there would be less need for overtaking at highway speeds.

• No literature reports of adverse safety impacts were found regarding implementation of on - board idle - reduction technologies in MD/HDVs (such as automatic start - stop, direct - fired heaters, and APUs).***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 6 • There was no clear consensus from the literature regarding the relative crash rates and highway safet y impacts of L CVs, due to lack of sufficient data and controls and inconsistent study

methodologies. Recent safety evaluations of LCVs and ongoing MAP - 21 mandated studies will clarify and quantify

this issue.

• Tire technologies for FE (including ATI S, TPMS, LRR and single - wide tires) literature raised potential safety concerns regarding lower stability or loss o f control, e.g., when tire pressure is uneven or a single wide tire blows out on the highway . However, sy stems such as automated tire monitoring s ys tems and stability enhancing electronic s ys tems (ABS, ESC, RSC) may compensate and mitigate any adverse saf et y impacts.

• Aerodynamic technologies that offer significant fuel savings have raised potential concerns about vehicle damage or injury in case of detached fairings or skirts, although there were no documented incidents of this ty pe in the literature.

• Some light weighting materials may pose some fire safety and crashworthiness hazards, depending on their performance in structural or other vehicle subsy stem applications (chassis, power - train, and crash box or safet y cage). Some composites (fiberglass, plastics, CFRC, foams) may become brittle on impact or due to weathering from UV exposure or extreme cold. Industry has developed advanced, high performance lightweight material options tailored to their automotive applications , e.g., thermoplastics resistant to UV and weathering. No examples of such lightweight material failures on MD/HDVs were identified in the literature. Chapter 3 provides complementary inputs on the potential safet y issues associated with FE technologies and alternative fuels obtained from Subject Matter Experts (SMEs). The broad cross - section of SMEs consulted had experience with the operation of “green” truck and bus fleets, were Federal program managers, or were industry developers of FE sy stems for MD/HDVs. Safet y concerns raised b y the SMEs can be prevented or mitig ated b y compl yi ng with applicable regulations and safety standards and best practices, and are being addressed b y evolving technologies, such as electronic collision prevention devices. Although SMEs raised some safet y concerns, their experience indicates that sy stem - or fuel - specific hazards can be prevented or mitigated by observing applicable industry standards, and b y training managers, operators and maintenance staff in safety best practices. Specific safet y concerns raised b y SMEs based on their exp erience included:

• Alternative fuels did not raise major safety concerns, but generall y required better education and training of staff and operators. There was a concern expressed regarding high pressure (4000 psi) CNG cylinders that could potentially exp lode in a crash scenario or if otherwise ruptured. However, aging CNG fuel tank safety can be assured b y enforcing regulations such as FMVSS No. 304, and b y periodic inspection***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 7 and end - of

- life disposal and replacement. A propane truck fleet manager state d that the fuel was as safe as or safer than gasoline, and reported no safety issues with the compan y’s propane, nor with hybrid gasoline - electric trucks. OEMs of drivetrain hy bridization and electrification sy stems, including advanced L ithium Ion batteri es for RESS, indicated that they undergo multiple safety

tests and are designed with fail safes for various misuse and abuse scenarios. Integration of h ybrid components downstream b y bodybuilders in retrofits, as opposed to new vehicles, was deemed a pote ntial safet y risk. Another potential safet y concern raised was the uncertain battery lifetime due to variability of climate, duty - cycles, and aging. Without state of - charge indicators, this could conceivably leave vehicles underpowered or stranded if the battery

degrades and is not serviced or replaced in a timel y manner.

• ITS and telematics raised no safet y concerns; on the contrary , fleet managers stated that “efficient drivers are safer drivers.” Monitoring and recording of driver behavior, combined with coaching, appeared to reduce distracted and aggressive driving and provided significant FE and safety benefits.

• A wide - base single tire safet y concern was the decrease in tire redundancy in case of a tire blowout at highway speeds. For LRRs, a co ncern was that they could negativel y affect truck stopping distance and stability control.

• A speed - limiter safet y concern was related to scenarios when such trucks pass other vehicles on the highway

instead of staying in the right - hand lane behind other v ehicles. By

combining speed limiters with driver training programs, overall truck safet y could actuall y improve, as shown b y international practice.

• Aerodynamic s ys tems’ safet y performance to date was satisfactory, with no instances of on - road detachin g. However, covering underside or other components with aerodynamic fairings can make them harder to inspect, such as worn lugs, CNG relief valve shrouds, wheel covers, and certain fairings. Drivers and inspectors need to be able to see through wheel cov ers and to be able to access lug nuts through them. These covers must also be durable to withstand frequent road abuse.

• For lightweighting materials, the safety concern raised was lower crashworthiness (debonding or brittle fracture on impact) and the potential for decreased survivability in vehicle fires depending on the specific material choice and its application. The key finding from the literature review and SME interviews is that there appear to be no major safet y hazards preventing the adoption of FE technologies, or the increased use of alternative fuels and vehicle electrification. In view of the scarcit y of hard data currentl y available on actual highway crashes that can be directly or causally

attributed to adoption of FE***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 8 technologies and/o r alternative fuels by MD/HDVs, and the limited experience with commercial truck and transit bus fleets operations equipped with these technologies, it was not possible to perform a quantitative, probabilistic risk assessment, or even a semi - quantitative p reliminary hazard anal ys is (PHA). Chapter 4 emplo ys a deterministic scenario - based hazard anal ys is of potential crash or other safet y concerns identified from the literature review or raised by subject matter experts (SMEs) interviewed (e.g., interfaces wi th charging or refueling infrastructure). For each specific hazard scenario discussed, the recommended prevention or mitigation options, including compliance with applicable NHTSA or FMCSA regulations, and voluntary industry standards and best practices are identified, along with FE technology or fuel - specific operator training. SMEs safety

concerns identified in Sec 3.3 were complemented with actual incidents, and developed into the hazard scenarios anal yz ed in Chapter 4. The scenario - based deterministic hazard analysis reflected not onl y the literature findings and SMEs’ safet y concerns, but also real truck or bus mishaps that have occurred in the past. Key hazard anal ys is scenarios included: CNG - fueled truck and bus vehicle fires or explosions due to tank rupture, when pressurized fuel tanks were degraded due to aging or when PRDs failed; LNG truck crashes leading to fires, or LNG refueling - related mish aps; the flammability or brittle fracture issues related to lightweighting materials in crashes; reduced safety performance for either LRR or wide - base tires; highway pile - ups when L CVs attempt to pass at highway speeds; aerodyn amic components detaching wh ile the vehicle traveled on a busy highway or urban roadway ; and fires resulting in overheated lithium ion batteries in electric or hy brid buses. These h ypothetical worst case scenarios appear to be preventable or able to be mitigated b y observing safet y regulations and voluntary standards, or with engineering and operational best practices. Chapter 5 reviews and discusses the existing federal and state regulatory framework for safel y operating MD/HDVs equipped with FE technologies or powered b y alternati ve fuels. The review identifies potential regulatory barriers to their large - scale deploy ment in the national fleet that could delay

achievement of desired fuel consumption and environmental benefits, while ensuring equal or better safety performance. Cha pter 6 summarizes the major findings and recommendations of this preliminary safet y anal ys is of fuel efficiency technologies and alternative fuels adopted by MD/HDVs. The scenario - based hazard analy sis, based on the literature review and experts’ inputs, indicates that MD/HDVs equipped with advanced FE technologies and/or using alternative fuels have manageable potentially

adverse safet y impacts. The findings suggest that the potential safety hazards identified during operation, maintenance, and crash scenarios can be prevented or mitigated b y compl yi ng with safet y regulations and voluntary standards and industry best practices. The study

also did not identify an y major regulatory barriers to rapid adoption of FE technologies and alternative fuels b y the MD/HDV fleet.***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 9 

### 9.5 **Oak Ridge National Laboratory (ORNL) Research on Low Rolling**  **Resistance Truck Tires** DOT’s Federal Motor Carrier Safety Administration and NHTSA sponsored a test program conducted b y Oak Ridge National Laboratory to explore the effects of tire rolling resistance levels on Class 8 tractor - trailer stopping distance performance over a range of loading and surface conditions. D The objective was to determine whether there is a relationship between tire rolling resistance and stopping distance for vehicles of this ty pe. The overall results of this research suggest that tire rolling resistance is not a reliable indicator of Class 8 tractor - trailer stopping distance. The correlation coefficients (R2 values) for linear regressions of wet and dry stop ping distance versus overall vehicle rolling resistance values did not meet the minimum threshold for statistical significance for an y of the test conditions. Correlation between CRR and stopping distance was found to be negligible for the dry tests for b oth loading conditions. While correlation was higher for the wet testing (showing a slight trend in which lower CRRs correspond to longer stopping distances), it still did not meet the minimum threshold for statistical significance. In terms of complianc e with Federal safety standards, it was found that the stopping distance performance of the vehicle with the four tire sets studied in this research (with estimated tractor CRRs which varied b y 33 percent ), were well under the FMVSS No. 121 stopping distan ce requirements. 

### 9.6 **Additional Safety Considerations** The agencies’ considered the Organic Rankine Cycle waste heat recovery (WHR) as a fuel saving technology

in the rulemaking timeframe. The basic approach of these s ys tems is to use engine waste heat from multiple sources to evaporate a working fluid through a heat exchanger, which is then passed through a turbine or equivalent expander to create mechanical or electrical power. The working fluid is then condensed as it passes through a heat exchanger and returns to back to the fluid tank, and pulled back to the flow circuit through a pump to continue the cycle. Despite the promising performance of pre - protot ype WHR s ys tems, manufacturers have not yet arrived at a consensus on which working fluid(s) to be used in WHR sy stem s to balance concerns regarding performance, global warming potential (GWP), and safety . Current working fluids have a high GWP (conventional refrigerant), are expensive (low GWP refrigerant), are hazardous (ammonia, etc.), are flammab le (ethanol/methanol), or can freeze (water). One of the challenges is determining how to seal the working fluid properl y under the vacuum condition with high temperature to avoid safety issues for flammable/hazardous working fluids. Because of these ch allenges, choosing a working fluid will be an important factor for sy stem safet y, efficiency, and overall production viability . The agencies believe manufacturers will require additional time and development effort to assure that a working fluid that is both appropriate, given the noted challenges, and has a low GWP for use in waste heat recovery sy stems. Based on this and other factors, the analy sis for the Preferred Alternative assumes that WHR would not achieve a significant market penetration for di esel tractor engines (i.e., greater

D Lascurain, M.B. (2015, June). “ Effects of tire rolling resistance levels on Class 8 tractor trailer stopping distance perfo rmanc e.” Washington, DC: National Highway Traffic Safety Administration.***** E.O. 12866 Review –**  **REVISED –**  **Do Not Cite, Quote, or Release During Review *****

9 - 10 than 5 percent) until 2027, which would provide time for these considerations to be addressed. The agencies assume no use of this technology in the HD pickups and vans and vocational vehicle segments. 

### 9.7 **The Agencies’ As sessment of Potential Safety Impacts**  NHTSA and EPA considered the potential safety i mpact of technologies that improve HD vehicle fuel efficiency

and GHG emissions as part of the assessment of regulatory alternatives. The safet y assessment of the technolo gies in this proposal was informed b y two NAS reports, an anal ys is of safety

effects of HD pickups and vans using estimates from the DOT report on the effect of mass reduction and vehicle size on safety, and agency- sponsored safet y testing and research. T he agencies considered safet y from the perspective of both direct effects and indirect effects. In terms of direct effects on vehicle safety, research from NAS and Volpe, and direct testing of technologies like the ORNL tire work, indicate that there are no major safety hazards associated with the adoption of technologies that improve HD vehicle fuel efficiency and GHG emissions or the increased use of alternative fuels and vehicle electrification. The findings suggest that the potential safet y hazards identified during operation, maintenance, and crash scenarios can be prevented or mitigated b y comp lyingwith safety regulations , voluntary standards and industry

best practices. Tire testing showed tire rolling resistance did not impact of Class 8 tractor - trailer stopping distance for the tires tested. Also, because the majority of HD pickup and van fleet are above 4,594 pounds, the vehicle mass reduction in HD pickup and vans is estimated to reduce the net incidence of highway fatalities. Taken together, these studies suggest that the fuel efficiency improving technologies assessed in the studies can be implemented with no degradation in overall safety. However, anal ys is anticipates that the indirect effect of the proposed standards, by reducing the operating costs, would lead to increased travel b y tractor - trailers and HD pickups and vans and, therefore, more crashes involving these vehicles.