Summary

BACKGROUND

Medium- and heavy-duty trucks, motor coaches, and transit buses—collectively, medium- and heavy-duty vehicles (MHDVs)1—are used in every sector of the economy. The purpose of these vehicles ranges from carrying passengers to moving goods. The fuel consumption and greenhouse gas (GHG) emissions of MHDVs have become a focus of legislative and regulatory action in the past few years. This report is a follow-on to the National Research Council’s (NRC’s) Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles (NRC, 2010; henceforth called the Phase One Report), issued March 31, 2010. That report provided a series of findings and recommendations on the development of regulations for reducing fuel consumption of MHDVs.

On September 15, 2011, the National Highway Traffic Safety Administration (NHTSA) and the U.S. Environmental Protection Agency (EPA), hereinafter referred to as the Agencies, jointly published a Federal Register notice (76 Fed. Reg. 57105) finalizing rules to establish a comprehensive Heavy-Duty National Program to reduce GHG emissions and fuel consumption for on-road MHDVs (the Phase I Rule, also know as the Phase I Regulation).

Subsequently, NHTSA entered into a cooperative agreement with the NRC to issue a report by 2016 on technologies and approaches to reducing the fuel consumption of MHDVs with a view toward beginning work on a revision to the Phase I Rule. The committee has since learned that NHTSA and EPA have commenced work on a second round (Phase II) of fuel consumption and GHG emission standards for MHDVs. This first report by the committee provides guidance for the Phase II Rule, which is directed at the post-2018 time frame.2 The committee’s final report, to be issued in 2016, will cover a broader range of technologies and issues and will address the 2025-2030 time frame.

COMPARISON OF PHASE I RULE WITH THE PHASE ONE REPORT

In 2010, the NRC prepared a report in preparation for the Phase I regulation, proposing several recommendations. On the whole, NHTSA was quite responsive to the Phase One Report, in particular to the matter of taking the Report’s advice on basing the standards on load-specific fuel consumption (LSFC)3 and using modeling to determine compliance. Some recommendations were not adopted by NHTSA, and the committee encourages NHTSA and EPA to do so. In particular, the following aspects remain valid: the importance of data acquisition on the baseline MHDV stock, sales, and performance, without which conclusions on whether the goals of the regulation are met, will necessarily be very uncertain; the formation of an expert group to review vehicle simulations, in particular for the Greenhouse gas Emissions Model (GEM); implementation of driver training programs that may enable reduced fuel consumption; and incremental fuel efficiency gains that could be obtained by dieselization of Classes 2b through 7 vehicles. There were other recommendations that NHTSA did not act on, but the above seem to the committee to be the most compelling.

CERTIFICATION USING MODELING AND SIMULATION

From both technical and operational perspectives there is an objective to improve, and even optimize, efficiency metrics for trucks in each class. The existing NHTSA and

______________

1 More precisely, these vehicles include those classified as Class 2b through Class 8, which as a group range in gross (combined) vehicle weight from 8,500 to 80,000 pounds.

2 This Summary contains the key recommendations from the committee’s report.

3 The precise metric for measuring fuel consumption, the LSFC is measured in gallons of fuel per payload ton per 100 miles. The lower the fuel consumption (FC) of the vehicle and the higher the payload the vehicle carries, the lower will be the LSFC.



The National Academies | 500 Fifth St. N.W. | Washington, D.C. 20001
Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement



Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 1
Summary BACKGROUND The committee’s final report, to be issued in 2016, will cover a broader range of technologies and issues and will address Medium- and heavy-duty trucks, motor coaches, and tran- the 2025-2030 time frame. sit buses—collectively, medium- and heavy-duty vehicles (MHDVs)1—are used in every sector of the economy. The purpose of these vehicles ranges from carrying passengers COMPARISON OF PHASE I RULE WITH THE PHASE to moving goods. The fuel consumption and greenhouse gas ONE REPORT (GHG) emissions of MHDVs have become a focus of legisla- In 2010, the NRC prepared a report in preparation for the tive and regulatory action in the past few years. This report Phase I regulation, proposing several recommendations. On is a follow-on to the National Research Council’s (NRC’s) the whole, NHTSA was quite responsive to the Phase One Technologies and Approaches to Reducing the Fuel Con- Report, in particular to the matter of taking the Report’s sumption of Medium- and Heavy-Duty Vehicles (NRC, 2010; advice on basing the standards on load-specific fuel con- henceforth called the Phase One Report), issued March 31, sumption (LSFC)3 and using modeling to determine compli- 2010. That report provided a series of findings and recom- ance. Some recommendations were not adopted by NHTSA, mendations on the development of regulations for reducing and the committee encourages NHTSA and EPA to do so. In fuel consumption of MHDVs. particular, the following aspects remain valid: the importance On September 15, 2011, the National Highway Traffic of data acquisition on the baseline MHDV stock, sales, and Safety Administration (NHTSA) and the U.S. Environmen- performance, without which conclusions on whether the tal Protection Agency (EPA), hereinafter referred to as the goals of the regulation are met, will necessarily be very Agencies, jointly published a Federal Register notice (76 uncertain; the formation of an expert group to review vehicle Fed. Reg. 57105) finalizing rules to establish a comprehen- simulations, in particular for the Greenhouse gas Emissions sive Heavy-Duty National Program to reduce GHG emis- Model (GEM); implementation of driver training programs sions and fuel consumption for on-road MHDVs (the Phase that may enable reduced fuel consumption; and incremental I Rule, also know as the Phase I Regulation). fuel efficiency gains that could be obtained by dieselization Subsequently, NHTSA entered into a cooperative agree- of Classes 2b through 7 vehicles. There were other recom- ment with the NRC to issue a report by 2016 on technologies mendations that NHTSA did not act on, but the above seem and approaches to reducing the fuel consumption of MHDVs to the committee to be the most compelling. with a view toward beginning work on a revision to the Phase I Rule. The committee has since learned that NHTSA and EPA have commenced work on a second round (Phase II) of CERTIFICATION USING MODELING AND SIMULATION fuel consumption and GHG emission standards for MHDVs. From both technical and operational perspectives there This first report by the committee provides guidance for the is an objective to improve, and even optimize, efficiency Phase II Rule, which is directed at the post-2018 time frame.2 metrics for trucks in each class. The existing NHTSA and 1 More precisely, these vehicles include those classified as Class 2b through Class 8, which as a group range in gross (combined) 3 The precise metric for measuring fuel consumption, the LSFC vehicle weight from 8,500 to 80,000 pounds. is measured in gallons of fuel per payload ton per 100 miles. The 2 This Summary contains the key recommendations from the lower the fuel consumption (FC) of the vehicle and the higher the committee’s report. payload the vehicle carries, the lower will be the LSFC. 1

OCR for page 1
2 REDUCING THE FUEL CONSUMPTION AND GHG EMISSIONS OF MEDIUM- AND HEAVY-DUTY VEHICLES, PHASE TWO EPA rules have already addressed the metrics to be employed rolling resistance, there needs to be high confidence in the for engine efficiency, vehicle efficiency, and the associated values inputted to GEM. carbon dioxide (CO2) emissions levels, for both gasoline and diesel. From a practical standpoint at the time of writing, the Recommendation S.3: A mechanism needs to be imple- rules also drive change to provide economic benefit to the mented for obtaining accurate tire rolling-resistance factors, truck user. However, as truck efficiency regulation advances, including equipment calibration, and maintaining that infor- there are trade-offs that must be addressed. Metrics of inter- mation in a public database. This might be managed in the est are fuel efficiency, GHGs, cost, criteria pollutants, and same way that tread wear, temperature, and traction data are energy security. The primary trade-off is GHGs versus fuel displayed through the federal Uniform Tire Quality Grading efficiency, when several fuels and their associated technolo- system. (Recommendation 3.4) gies are considered. GEM employs a limited set of cycles to challenge the Recommendation S.1:  NHTSA, in consultation with EPA, simulated truck. These cycles do not include real-world should consider carefully the impact on related metrics when road grade and neglect varying operating weights and aero- attempting to optimize for a single metric, or should other- dynamic yaw angles. Being speed-time based, these cycles wise establish a clearly articulated objective that weights, or also do not allow for the faster acceleration of more power- places limits upon, relevant metrics. (Recommendation 3.1) ful trucks, or the longer time that might be taken by less powerful trucks to complete some real-world distance-based GEM is a relatively simple model focused on aerodynam- routes. This deficiency is not evident in the current model, ics, rolling resistance, speed, weight, and idle control, and as where a hard-coded engine map, rather than a real OEM such it is not capable of acknowledging efficiency and GHG engine model, is used. emissions changes associated with engine and transmission design, the integration of advanced power trains, alternative Recommendation S.4:  The choice of test cycles and routes fuels, hybrid and electric vehicles, and optimal component or schedules used in GEM needs to be readdressed thor- management. The weight reduction input in GEM is limited oughly to avoid creating designs that are optimized for the to a fixed set of technologies and parts. GEM upgrades are test rather than for achieving real-world performance in the required to provide more realistic prediction of fuel use and design process. (Recommendation 3.6) GHG emissions, particularly as detailed in the next three recommendations. FLEET DATA Models should be capable of simulating real-world com- ponent behavior accurately and should not be oversimpli- A further issue of importance is the need to collect data fied. GEM specifically does not allow for synergy between on vehicles such as would permit regulators to evaluate the components, the operation or control of components in a regulatory efficacy and improve both the accuracy of the most efficient way, or the engendering of efficiency through Phase I Rule and any subsequent phases. NHTSA did not operation of a smaller component at higher relative load. include a pilot phase when it promulgated the Phase I Rule GEM specifies the performance maps for major components in 2011. Thus there were no baseline data from even a few such as the engine and transmission and does not credit the representative national fleets prior to the rulemaking, such vehicle manufacturer with benefits of using a potentially as would have enabled comparison with post-rulemaking superior engine or transmission. fuel efficiency. This would have also started to facilitate the comparison of real-world test data with compliance data. The Recommendation S.2:  NHTSA should investigate allowing committee nonetheless recognizes that NHTSA has begun the original equipment manufacturer (OEM) to substitute the process of designing surveys and seeking the necessary OEM-specific models or code for the fixed models in the Office of Management and Budget approvals to allow it to current GEM, including substituting a power pack (the assemble a picture of the fleet characteristics, including the engine, aftertreatment, transmission). These models, whether collection of R.L. Polk registration data and forecasts, which provided by OEMs or fixed in the code, should be configured is appropriate for Class 2b to Class 8 vehicles. to reflect real-world operation accurately. (Recommendation 3.7) Recommendation S.5:  NHTSA should establish a repeat- able, reliable data collection process as soon as possible. In Calibration of equipment traceable to national standards addition to continuing data procurement with SwRI and R.L for passenger car tires is in place, and self-calibration of Polk, NHTSA should investigate outside sources—such as equipment is in place for the grading of tires in Europe. FTR, ACT Research, SmartWay, the North American Coun- Calibration of tire characterization equipment for U.S. cil for Freight Efficiency (NACFE), and the American Trans- regulations should be extended to cover all measurements portation Research Institute (ATRI)—to obtain a repeatable, of coefficients of rolling resistance used in GEM. For tire reliable baseline as well as future data. These sources could

OCR for page 1
SUMMARY 3 use the R.L. Polk data and conduct clarifying, deeper inter- Due to the economics-driven rapid adoption of natural views with truck and trailer builders, manufacturers, and gas, there is urgency to develop an optimum solution in fleets to elicit specific ongoing data on technologies procured Phase II Rule standards for both GHG emissions and fuel and fuel consumption. (Recommendation 4.2) consumption (as well as criteria emissions) that will accom- modate this fuel without artificially disrupting prevailing commercial transportation business models. As a specific NATURAL GAS example, the GEM certification tools need to include natural Natural gas accounts for about 25 percent of all U.S. gas engine maps to more accurately quantify the emissions energy use, yet only 0.1 percent is used in transportation, and fuel economy of natural gas vehicles. equivalent to about 0.5 billion gallons per year of petroleum fuel. However, in the short time since the release of the Recommendation S.8:  To benefit fully from the GHG and Phase One Report (NRC, 2010), natural gas has emerged as petroleum displacement potential of natural gas, govern- an economically attractive option for commercial vehicles. ment and the private sector should support further technical This has been driven by the rapid development of low-cost improvements in engine efficiency and operating costs, production of unconventional natural gas. reduction of storage costs, and emission controls (as is done In order for medium and heavy trucks to use natural gas for diesel engines). NHTSA and EPA should also evaluate fuel rather than diesel, the most significant changes needed the need for and benefits and costs of an in-use natural gas are the onboard fuel storage method and the means of fuel specification for motor vehicle use. (Recommendation introducing and igniting the fuel in the engine. Onboad fuel 5.4) storage is by high pressure, effected by either compressed natural gas (CNG) cylinders (3,600 pounds per square inch is REGULATING TRAILERS typical) or cryogenic containers filled with liquefied natural gas (LNG). For using natural gas in place of gasoline, the Aerodynamic Devices for Trailers spark ignition engine carries over with modest changes, but fuel storage is still by one of the above two methods. There are four regions of the tractor–van trailer combina- Natural gas engines are well developed, although improve- tion truck that are amenable to aerodynamic design improve- ments can be pursued in engine efficiency, maintenance ments, including the various tractor details, the tractor-trailer costs, and onboard vehicle storage costs. Natural gas’s inher- gap, the trailer underbody, and the trailer tail. Side skirts ent GHG benefit by virtue of its low carbon content (~28%) constitute 90 percent of devices sold to improve aerodynam- is partially negated by lower efficiency in currently available ics. Most side skirts provide a 5 percent fuel saving at 65 mph engines and the higher GHG impact of methane emissions. (3 percent at 55 mph) on EPA testing as part of SmartWay.4 In addition, a natural gas leakage correction to GHG impact A recent study identified barriers to use of trailers that are could negate the inherent tailpipe CO2 advantage. more aerodynamically efficient (NACFE and Cascade Sierra Solutions, 2013), primarily related to understanding of cost- Recommendation S.6:  NHTSA and EPA should develop benefit data and lack of robust application information. Yet, a separate standard for natural gas vehicles as is presently early adopting carriers indicate there is a good return on the case for diesel- and gasoline-fueled vehicles. Factors the investment from their use. Nonetheless, manufacturers of Agencies should consider in setting the standard include the trailer side skirts report sales doubled between 2012 and maximum feasible ability of natural gas engines to achieve 2013. The manufacturers also report installed prices of side reductions in GHG emissions and fuel consumption, the skirts have declined by half. uncertainties involved with the various alternatives, the A California regulation requires operators of van trailers impact of duty cycles on the ability to comply with the vehi- to use aerodynamic devices to reduce the energy required cle standards, the cost of the technology, and rapid growth to pull them. Observations made in California and Arizona of the market for natural gas engines and vehicles. This may showed a greater proportion of trailers with aerodynamic require additional focused studies. (Recommendation 5.2) devices than did those observations made in Oregon, Texas, Michigan, Pennsylvania, and Maryland. Side skirts were Recommendation S.7:  More studies and data are needed overwhelmingly the predominant aerodynamic devices strat- to determine the well-to-tank GHG emissions of natural gas egy. Other strategies (underbody fairings and rear fairings) vehicles, since current estimates vary significantly regarding were observed in just a few instances. quantification of emissions leakage of methane. EPA and NHTSA should assemble a best estimate of well-to-tank 4 SmartWay is a voluntary program administered by EPA that GHG emissions to be used as a context for developing future was formed in 2004 with the objective of improving efficiency and rulemakings. (Recommendation 5.1) reducing fuel consumption and pollution from movement of freight across the supply chain. Currently it focuses mainly on over-the- road trucking.

OCR for page 1
4 REDUCING THE FUEL CONSUMPTION AND GHG EMISSIONS OF MEDIUM- AND HEAVY-DUTY VEHICLES, PHASE TWO Recommendation S.9:  NHTSA, in coordination with EPA, full-vehicle test procedure and process and should validate should adopt a regulation requiring that all new 53 foot and the improved procedure against real-world vehicle testing. longer dry van and refrigerated van trailers meet performance Further, the Agencies should assess if adding yaw loads to standards that will reduce their fuel consumption and CO2 the validation process provides significantly increased value emissions. The lead time to implement this regulation should to the drag coefficient (Cd) result. In addition, the Agen- be evaluated independently from lead time requirements cies should disseminate to end users updated test data and applicable to the next set of standards for new engines and fuel savings of efficient trailers, aerodynamic devices, and tractors, because less time is needed to perform compliance tires, especially to those not participating in the SmartWay testing and install aerodynamic devices on new trailers. The program. This should increase end user confidence in fuel agencies should also collect real-world data on fleet use of savings and device reliability. (Recommendation 6.3) aerodynamic trailers to help inform the regulation. (Recom- mendation 6.1) Tires The current SmartWay program and CARB regulation Many new tractors and most new trailers are equipped only address the most commonly used 53+ foot van trailer, with low-rolling-resistance tires that meet the SmartWay per- which accounts for about 60 percent of the trailers that formance standard, and this is likely to increase due to regu- could potentially benefit from use of aerodynamic devices. latory requirements. However, 70 percent of new tires sold Use of aerodynamic devices on other types of trailers, in 2012 for use on tractors and trailers were for replacement such as container/chassis and shorter vans including dual of existing tires, and only 42 percent of these are SmartWay trailers (“pups”), could provide additional fuel savings of verified. There is no assurance in the future that replacement 4 to 9 percent per tractor-trailer, according to industry esti- tires will be as energy efficient as the original equipment tires mates. Fuel savings from use of side skirts have also been they replace. Manufacturers have also introduced wide-base demonstrated on flatbed trailers. The cost-effectiveness of single tires (WBSTs), many of which feature lower rolling using aerodynamic devices on these additional categories of resistance than most dual-tire sets. WBSTs make up less than trailers depends on their annual mileage accumulation and 10 percent of the commercial truck tire market, but their use average speed, among other considerations such as access is increasing as fleets strive to reduce fuel consumption and to the trailer underbody, and needs further assessment and GHG emissions.  quantification. Recommendation S.12:  NHTSA, in coordination with Recommendation S.10:  NHTSA, in coordination with EPA, should further evaluate and quantify the rolling resis- EPA, should determine whether it would be practical and tance of new tires, especially those sold as replacements. cost-effective to include along with the regulation of van If additional cost-effective fuel savings can be achieved, trailers the regulation of other types of trailers such as pups, NHTSA should adopt a regulation establishing a low-rolling- flatbeds, and container carriers, as doing so could substan- resistance performance standard for all new tires designed tially increase overall fuel savings. (Recommendation 6.2) for tractor and trailer use. (Recommendation 6.5) Various complete truck test procedures, such as the Soci- Precision in tire rolling resistance coefficient (Crr) mea- ety of Automotive Engineers (SAE) J1321 and coast-down surement is mandatory. Further, while the ISO28580 test procedure SAE J1263, used for determining the effective- procedure is given good grades by most in the industry, a ness of aerodynamic devices, are not sufficiently precise robust machine cross-correlation does not exist for com- to discern small incremental changes. Alternatives such as mercial vehicle tires in the United States. Carriers cannot wind tunnel testing and computational fluid dynamics (CFD) depend on the comparability of Crr for measurements from simulation should be evaluated because they provide fidel- approximately 60 tire suppliers verified by SmartWay. ity and better precision. These methods can reduce the cost of development validation, may avoid building of multiple Recommendation S.13:  NHTSA, supported by EPA, full-size prototypes, and can accelerate development time should expeditiously establish and validate the equipment for the final product. Better test precision and repeatability and process for a tire industry machine alignment laboratory may induce otherwise skeptical end users to adopt such and mandate the use of that laboratory by each tire manu- technologies. facturer seeking Crr validation for any tires being offered as candidates in the GEM computation process, just as the Crr’s Recommendation S.11:  NHTSA should evaluate the of light-duty-vehicle tires were validated. (Recommendation relative fidelities of the coast-down procedure and candi- 6.6) date powered procedures to define an optimum prescribed

OCR for page 1
SUMMARY 5 OTHER APPROACHES TO REDUCING FUEL methyl tertiary butyl ether (MTBE) to gasoline as an oxygen- CONSUMPTION ate intended to reduce ground-level ozone. The Phase I Rule had the effect of encouraging the adop- Recommendation S.15:  NHTSA, in coordination with tion of technologies for reducing fuel consumption. Such EPA, should begin to consider the well-to-wheel, life-cycle reductions can be achieved by technological improvements energy consumption and greenhouse emissions associated to the vehicle as well as by improvements in operations, with different vehicle and energy technologies to ensure changes in behavior of drivers, and so forth. The Phase One that future rulemakings best accomplish their overall goals. Report considered other approaches (referred to, perhaps (Recommendation 1.10) imprecisely, as nontechnical approaches) such as intelligent transportation systems; construction of lanes exclusively for Recommendation S.16:  NHTSA should conduct an analy- trucks; congestion pricing; driver training; and intermodal sis, including methods such as expert surveys and scenario operations (NRC, 2010, pp. 159 et seq.). Also considered analysis or red teaming, as appropriate, to anticipate and were market-based instruments such as fuel taxes. Another analyze potential unintended consequences of its regulations viable approach would entail adjusting size and weight and to determine whether additional actions are warranted to restrictions on trucks. For example, this might include greater try to minimize such impacts. NHTSA should undertake this use of vehicles that have favorable LSFC such as longer analysis concurrently with its next revision to its regulation. combination vehicles, which have greater freight capacity (Recommendation 1.4) than the notional tractor-trailer, which can have a combined gross vehicle weight of 80,000 lb.5 While some nonvehicle Regarding the potential for technological change in the alternative approaches for reducing fuel consumption and MY2019-2022 time frame, the committee, in its investiga- greenhouse gas emissions may be beyond NHTSA’s del- tions to date, has not identified any combustion or other egated authority, the agency can work with other agencies engine technologies beyond those identified in the NRC with appropriate authority as well as encourage private (2010) Phase One Report that would provide significant actors to consider such strategies to complement and support further fuel consumption reduction during the Phase II Rule NHTSA’s standards. time frame. However, those technologies identified in the Phase One Report should be updated with current projec- Recommendation S.14:  NHTSA should consider addi- tions for fuel consumption reduction and adjusted for system tional strategies to encourage the adoption of measures interactions when used in combination with each other. that reduce fuel consumption by attempting to quantify the A further issue relates to the timing and rate at which impacts of nontechnological factors on the costs and feasibil- technology enters the marketplace. In establishing the strin- ity of future efforts to improve fuel consumption. (Recom- gency of a Phase II Rule, careful evaluation of technology mendations 1.9 and 1.11) penetrations is necessary. While the NHTSA-stated intent of the Phase I Rule was to base targets on off-the-shelf tech- REGULATORY PROCESSES nologies, the new baseline for setting a Phase II Rule will be drawn from more current vehicles and will include con- The committee also has made several observations about sideration of the different degrees of penetration attained by the regulatory process. Currently NHTSA and EPA stan- both off-the-shelf and future/advanced technologies by 2018. dards consider fuel efficiency of the vehicle (in gallons per ton-mile) and tailpipe CO2 emissions (in grams of CO2 per Recommendation S.17:  NHTSA’s Phase II Rule should ton-mile) that need to be achieved, on average, by the mix of take the current and projected incremental fuel consumption vehicles sold each year by each manufacturer. Manufacturers reductions and penetration rates of the various technologies are likely to achieve these vehicle standards using a variety into careful consideration: These incremental reductions of different energy fuels and technologies. Failure to consider and penetration rates should be updated from those that the well-to-wheel emissions of each combination of fuel were projected in the Phase I rulemaking. Furthermore, and vehicle technology may lead to regulations that do not system interactions should be evaluated for the effect on the achieve the anticipated energy and GHG emissions savings. projected incremental reductions whenever combinations of Further, there is the possibility that regulations could pro- technologies are considered. (Recommendation 2.2) duce incentives and behaviors that may result in unintended consequences that could be beneficial or detrimental, such as the water contamination that resulted from the addition of REFERENCES National Highway Traffic Safety Administration (NHTSA). 2010. Fac- 5 This follows from the observation that “weighing out” is better tors and Considerations for Establishing a Fuel Efficiency Regulatory for fuel consumption than “cubing out,” which refers to filling up Program for Commercial Medium- and Heavy-Duty Vehicles. DOT HS the cargo area before reaching the combined gross vehicle weight 811 XXX. Available at http://www.nhtsa.gov/staticfiles/rulemaking/pdf/ limit. cafe/NHTSA_Study_Trucks.pdf.

OCR for page 1
6 REDUCING THE FUEL CONSUMPTION AND GHG EMISSIONS OF MEDIUM- AND HEAVY-DUTY VEHICLES, PHASE TWO National Research Council (NRC). 2010. Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles. Washington, D.C.: The National Academies Press. North American Council for Freight Efficiency (NACFE) and Cascade Sier- ra Solutions. 2013. Barriers to the Increased Adoption of Fuel Efficiency Technologies in the North American On-Road Freight Sector. July.