8
Approaches to Fuel Economy and Regulations

This chapter examines the broad variations in medium-and heavy-duty vehicles and explains how the complex nature of trucks influences regulatory options. It explores metrics that capture the work task of the vehicle, thereby providing a means for comparing the relative fuel consumption performance of vehicles on the basis of task. The chapter concludes with a discussion of regulatory approaches and includes examples of fuel consumption regulatory instruments that may be suitable for implementation.

Thirty years ago, the National Highway Traffic Safety Administration (NHTSA) of the U.S. Department of Transportation was faced with the question of how to design a new fuel economy regulation for passenger vehicles. For many important elements, NHTSA was able to build off an existing exhaust emissions program. The regulated parties (vehicle manufacturers), test method (chassis dynamometer), and test cycle (federal test procedure) were adopted by NHTSA for its new fuel economy program. Of course, there were many important elements of the program that were unique to the new fuel economy regulation, such as the method of allowing compliance by means of a corporate average of annual sales and the development of a second test cycle to reflect highway operation.

Today, while there is an existing heavy-duty vehicle exhaust emissions program with its own regulated entities (engine manufacturers), test method (engine dynamometer), and test cycles (Federal Test Procedure [FTP], Supplemental Emissions Test [SET], Ramped Mode Cycle [RMC], and in-use tests), there are factors associated with the U.S. vehicle market that make fuel consumption regulations more difficult and complicated than the design of fuel economy standards for passenger vehicles. Consider the following three examples:

  • The heavy-duty vehicle market is extremely diverse, with a wide range of vehicle types, sizes, and duty cycles.

  • Heavy-duty vehicle manufacturing is driven by customer specifications, which often leads to a far greater variety of pairings between major components (e.g., engine, transmission, chassis, axles, wheels, body shape).

  • Unlike passenger vehicles, vehicle manufacturing is often split between two different manufacturers: the producer of the chassis and a second manufacturer that purchases the chassis, adds a body and special equipment, and ultimately sells the vehicle to the consumer (see Figure 8-1). The exception is pickup trucks and truck tractors, which are completely assembled by the final manufacturer.

PURPOSE AND OBJECTIVES OF A REGULATORY PROGRAM

The purpose and structure of a regulatory program should be as follows: (1) generate cost-effective reductions in fuel consumption from medium- and heavy-duty vehicles, maximizing the savings of fuel at a justifiable cost imposed on the industry and society; (2) accelerate the research, development, and market penetration of new and existing energy saving technologies; (3) reduce the amount of energy consumed per movement of freight or passengers; (4) build on existing market incentives and company practices to lower fuel consumption; and (5) minimize additional administrative burden upon the regulated industry.

There are a handful of major technical and policy questions that must be addressed when developing a new regulatory program. Each is discussed in turn throughout this chapter:

  • Regulated vehicle types. What types of vehicles should be regulated?

  • Regulated parties. Who should the regulated parties be?

  • Metrics for fuel consumption. What metric should be used to measure performance?



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8 Approaches to Fuel Economy and Regulations This chapter examines the broad variations in medium- tomer specifications, which often leads to a far greater and heavy-duty vehicles and explains how the complex variety of pairings between major components (e.g., nature of trucks influences regulatory options. It explores engine, transmission, chassis, axles, wheels, body metrics that capture the work task of the vehicle, thereby shape). providing a means for comparing the relative fuel consump- • Unlike passenger vehicles, vehicle manufacturing is tion performance of vehicles on the basis of task. The chapter often split between two different manufacturers: the concludes with a discussion of regulatory approaches and producer of the chassis and a second manufacturer that includes examples of fuel consumption regulatory instru- purchases the chassis, adds a body and special equip- ments that may be suitable for implementation. ment, and ultimately sells the vehicle to the consumer Thirty years ago, the National Highway Traffic Safety (see Figure 8-1). The exception is pickup trucks and Administration (NHTSA) of the U.S. Department of Trans- truck tractors, which are completely assembled by the portation was faced with the question of how to design a new final manufacturer. fuel economy regulation for passenger vehicles. For many important elements, NHTSA was able to build off an existing PURPOSE AND OBJECTIVES OF A REGULATORY exhaust emissions program. The regulated parties (vehicle PROGRAM manufacturers), test method (chassis dynamometer), and test cycle (federal test procedure) were adopted by NHTSA for The purpose and structure of a regulatory program should its new fuel economy program. Of course, there were many be as follows: (1) generate cost-effective reductions in fuel important elements of the program that were unique to the consumption from medium- and heavy-duty vehicles, maxi- new fuel economy regulation, such as the method of allow- mizing the savings of fuel at a justifiable cost imposed on ing compliance by means of a corporate average of annual the industry and society; (2) accelerate the research, devel- sales and the development of a second test cycle to reflect opment, and market penetration of new and existing energy highway operation. saving technologies; (3) reduce the amount of energy con- Today, while there is an existing heavy-duty vehicle sumed per movement of freight or passengers; (4) build on exhaust emissions program with its own regulated entities existing market incentives and company practices to lower (engine manufacturers), test method (engine dynamometer), fuel consumption; and (5) minimize additional administra- and test cycles (Federal Test Procedure [FTP], Supplemental tive burden upon the regulated industry. Emissions Test [SET], Ramped Mode Cycle [RMC], and There are a handful of major technical and policy ques- in-use tests), there are factors associated with the U.S. ve- tions that must be addressed when developing a new regu- hicle market that make fuel consumption regulations more latory program. Each is discussed in turn throughout this difficult and complicated than the design of fuel economy chapter: standards for passenger vehicles. Consider the following three examples: • Regulated ehicle types. What types of vehicles should be regulated? • The heavy-duty vehicle market is extremely diverse, • Regulated parties. Who should the regulated parties with a wide range of vehicle types, sizes, and duty be? cycles. • Metrics for fuel consumption. What metric should be • Heavy-duty vehicle manufacturing is driven by cus- used to measure performance? 

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0 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES FIGURE 8-1 Shared responsibility for major elements that affect heavy-duty-vehicle fuel efficiency. SOURCE: Bradley and Associates Figure 8-1 Shared responsibility for major elements that aff.eps (2009). bitmap--legibility is degraded • Methods for certification and compliance. What meth- use segment is the Class 2B, which makes up the majority ods will be used to determine compliance and overall of heavy-duty vehicles (53 percent) and which is responsible program effectiveness? for just under 20 percent of fuel consumption. The third larg- • Regulatory model. est class is Class 6. These are considered medium heavy-duty and generally have only a single rear axle, while Class 8 vehicles typically have tandem drive axles. Class 6 vehicles REGULATED VEHICLE TYPES make up about 16 percent of the heavy truck population The committee has considered a broad range of vehicles. and consume 11 percent of the fuel. Table 8-1 gives more These include pickup trucks, transit buses, motor coaches, detail. school buses, delivery vans, straight trucks, and combination Most Class 8 vehicles are combination trucks for which vehicles such as tractor trailers. The largest fuel use from the several trailer options are available to complete the vehicle heavy-truck fleet is associated with the vehicles that move system (see Figure 8-2), adding another dimension to an the vast majority of the freight: Class 8 tractor trailers with already complex regulatory challenge. For example, the type gross combined weight (GCW) ranging from 80,000 lb on of trailer used will influence the vehicle’s overall aerody- the interstate and in excess of 130,000 lb on some state high- namic drag coefficient and the projected frontal area, both of ways (GCW varies considerably, as it is governed by federal which influence aerodynamic losses and directly affect fuel and state size and weight regulations). This is not surpris- consumption. The tires, on both the tractor and the trailer, ing, considering the huge jump in weight hauling capacity will influence the rolling resistance. In addition, weight and between Class 8 (in excess of 130,000 lb) and the rest of the dimension regulations define the “legal” GVW, which also heavy-duty fleet (Class 2b through 7 weight capacity ranges influences fuel consumption. An added complication is that from 8,500 to 33,000 lb). Class 8s are about 20 percent of the size and weight regulations for a given vehicle vary de- the fleet in total number of vehicles, but 61 percent of the pending on the jurisdiction—federal or state. fuel use of all heavy-duty vehicles. The second largest fuel The problems are compounded further in that vehicles TABLE 8-1. Mileage and Fuel Consumption by Vehicle Weight Class Population Annual Miles Annual Fuel Use Percent of Percent of Percent of Vehicle (millions) (million) (million gallons) Population Annual Miles Fuel Use Class 2B 5.800 76,700 5,500 52.8 35.1 19.3 Class 3 0.691 9,744 928 6.3 4.5 3.3 Class 4 0.291 4,493 529 2.6 2.1 1.9 Class 5 0.166 1,939 245 1.5 0.9 0.9 Class 6 1.710 21,662 3,095 15.6 9.9 10.9 Class 7 0.180 5,521 863 1.6 2.5 3.0 Class 8 2.154 98,522 17,284 19.6 45.1 60.8 Total 10.992 218,580 28,444 100.0 100.0 100.0 SOURCE: DOT (2002).

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS FIGURE 8-2 Illustration of diversity of trailer and power unit (tractor) options. Figure 8-2 Illustration of diversity of trailer and power un.eps bitmap haul freight of various shapes, sizes, and densities and are vehicles (LDVs), in which cars were reclassified as light often loaded below capacity. While van trailers present a trucks to achieve less stringent regulatory standards. Related convenient and predictable space envelope for aerodynamic to “reclassification” is a potential for change in market be- evaluation, other trailers such as flat-decks have no such havior to avoid higher prices due to regulation (i.e., if Class fixed outer shell, and therefore the shape of flat deck trailers 2b is regulated but not Class 3 then buyers might buy more will change with each load transported, which in turn influ- of the larger Class 3 trucks because they would become less ences aerodynamic drag and thus fuel consumption. expensive relative to 2b trucks). Given the complexity and challenge of establishing a Second, while regulation of medium- and heavy-duty new regulatory policy for medium- and heavy-duty vehicles, vehicles is complicated, there could be further complications there could be a tendency to narrow the scope of a regulation, created by seeking to draw artificial lines between various or at least to focus early implementation, on the largest fuel segments. For example, Class 8 straight/vocational trucks users in the fleet. This would suggest focusing on Class 8, typically have two drive axles and Class 7 trucks have one. Class 6, and Class 2b vehicles to cover roughly 90 percent of Class 5 and Class 6 trucks are similar to each other, and the fuel use in the medium- and heavy-duty vehicle fleet. Classes 2b and 3 tend to be more similar to each other. While starting with a subset of heavy-duty vehicles is Third, when considering a regulatory framework, there tempting, there are several drawbacks that should be con- are a number of important parameters beyond fuel use, such sidered. Uneven policy application will cause disruptions as cost effectiveness, equity among manufacturers, potential in the marketplace and create the potential for reclassifying for gaming, minimizing unintended outcomes, and technol- various classes of vehicles, as has been done in light-duty ogy potential. Finally, Congress instructed NHTSA to estab-

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES lish fuel economy standards for medium- and heavy-duty from one another. These are (1) the wheels and tires yielding vehicles—not a portion or subset of medium- and heavy-duty tire rolling resistance, (2) the body-yielding aerodynamic vehicles. losses and (3) the power train. Arguably there is a fourth notable category of energy consumption-auxiliaries, that be considered, but is not as clearly separable. Vehicle chassis REGULATED PARTIES represents a structure that simply connects the body and There are at least two principal considerations to be evalu- the power train, and may be regarded as part of the power ated when seeking to determine the most effective point of train or part of the body for testing purposes. These are the regulation. The first practical consideration is that the num - key features that affect fuel consumption in some way. The ber of regulated entities must be a manageable number (in vehicle weight and aerodynamics are affected by the hood, the tens rather than the hundreds) of parties to limit compli- cab, skirts, bumpers and overall shape and design of the ance and administrative burdens. Second, to be effective, the vehicle body. The power train consists of the engine, hybrid regulation must affect the corporate parties with the greatest components, transmission, differentials, and drive axles. In control and authority over vehicle design and over those considering the entity to regulate, those responsible for the components that offer the potential for substantial reductions total vehicle or for each/any of these major components are in fuel consumption. among the options. Table 8-2 lists the advantages and disadvantages of each choice of regulated party. Regulating at the point of the en- Market Concentration gine manufacturer is likely to impose the lowest additional As discussed in Chapter 2, the majority of production administrative burden but limits the program to a small sub- of commercial trucks is concentrated in about 12 major set of potential reductions in fuel use. A second option is to corporations that control different portions of the market. impose regulation on the power train integrator, which could Manufacture of class 8 trucks (tractors and straight) is domi - be an engine company partnered with a drive train compo- nated by four companies (Daimler AG, Volvo, PACCAR, and nent supplier (e.g., hybrid component manufacturers), or a Navistar) that account for more than 90 percent of U.S. truck power train integrator could be an integrated truck OEM with registrations. The smallest heavy-duty vehicles—Class 2b to selected suppliers. This option would benefit from account- Class 4—are dominated by the Big 3 U.S. auto manufactur- ing for engine and power train improvements, but would, ers with 89 percent of registrations. in some cases, require greater integration of the existing Large original equipment manufacturers (OEMs) with industry. Regulation of the vehicle manufacturers offers the significant engineering capability design and manufacture greatest amount of potential improvements while limiting the almost all Class 2b, 3, and 8b (semitractors) vehicles. These number of regulated parties, but the administrative burden OEMs have design control over features that determine the will be substantially higher, particularly for smaller vehicle completed vehicle aerodynamics. In some cases, these OEMs manufacturers. make the engine and driveline components, while in others In the final analysis, the concept of addressing the power these are outsourced to specialist suppliers, who could be train, aerodynamics, and tires seems to have strong potential given responsibility for regulatory compliance of the power for success as it would maintain focus on the dominant fuel- train. For Classes 4 through 8a, there is a mix of vehicles consumption-related components of vehicles. The suppliers made by large and small OEMs and smaller final-stage of these components are arguably in the best position to con- manufacturers. The vehicle mix includes box trucks, bucket trol future improvements of the components that they manu- trucks, school buses, transit buses, motor coaches, refuse facture. The final stage manufacturers need some means of haulers, and dump trucks (see Chapter 6). These small enti- assurance that they receive accurate and meaningful data ties purchase the chassis, engine, driveline, and in some cases from the suppliers in order to evaluate the final vehicle fuel complete cab and chassis units from suppliers who could be consumption. Therefore, the point of regulation would need made responsible for regulatory compliance. In some cases to be at the final-stage vehicle manufacturer, supplemented the supplier content will determine aerodynamic character- by the provision of consistent component performance data istics, but in many cases, the final-stage manufacturer will by the component manufacturers. Annex 8-1 presents a more significantly influence aerodynamic characteristics. Given detailed analysis of a methodology that might underlie a the very limited engineering resources available to these component-based regulatory program. smaller OEMs, it is unreasonable to assume that such small A perplexing problem for any option, regarding Class 8 companies can conduct the necessary aerodynamic tests for vehicles, is what to do about the trailer. The trailer market each specialty vehicle produced. represents a clear barrier with split incentives, where the owner of the trailer often does not incur fuel costs, and thus has no incentive to improve aerodynamics of the trailer itself Control Over Design and Important Components or to improve the integration of the trailer with the tractor A vehicle may be considered as consisting of three major or truck. Furthermore, legal authority is tenuous, given that energy-consumption-related components that are separable trailers are not self-propelled vehicles. One option could be

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS TABLE 8-2 Advantages and Disadvantages of Each Choice of Regulated Party Regulated Entity Advantages Disadvantages Engine • Utilizes existing regulatory framework for criteria pollutants: • Misses the bulk of potential improvements in drivetrain, manufacturer test cycle (though current cycles may need updating), engine hybrids, tires, aerodynamics, vehicle accessories, tests, compliance testing component integration, improved design • Manageable number of regulated parties • Does not include trailer • Low administrative burden Power train • Captures hybrid systems and transmission packages when • May require two or more industry entities to define the integrator the dynamic power train system is broader than engine power train hardware as team; new business model in • Builds on existing regulatory framework of engine tests and some cases cycles • Will require upgrades to certification engine cell controls • Allows vehicle and trailer attributes to be covered by to accommodate range of vehicle load inputs and hybrid simulation with test cycles drive train components • Reduces need for full vehicle testing Final stage • Includes nearly all vehicle parameters that affect fuel use in • Class 8 trailers and bodies of vocational trucks not vehicle single heavy-duty vehicles included manufacturer • Manageable number of regulated parties • Higher administrative costs to develop test cycles, conduct vehicle testing, perform certification and compliance testing Fleet owner • Allows for greater range of operational improvements • Unmanageable number of regulated entities (hundreds of Vehicle owner (driver training, intermodalism) fleets: half of heavy-duty vehicles in fleets of less than 10 trucks) • Would still require mandatory fuel efficiency testing of HDVs to provide fleet owners with information required to make smart compliance decisions to allow manufacturers to certify for additional credits if an metric is strongly recommended as it will more adequately improved trailer design and/or integration is satisfactorily address the advisory principals above. incorporated as a complete vehicle. However, in many cases The practical effect of using a gallon per mile metric tractors change semitrailers frequently, making integration is that it will result in improvements only to the vehicle difficult without standardization of design. itself and in all likelihood encourage smaller vehicles with smaller payloads, resulting in serious erosion of transporta - tion efficiency. On the other hand, the load specific fuel METRICS FOR FUEL CONSUMPTION consumption (LSFC) metric such as gallons per cargo ton- Considering the complexity of heavy-duty vehicles and mile will promote technical improvements and configuration the highly specialized nature of vehicle design and operation development that increase the amount of cargo that can be with respect to vehicle task, the following advisory principles carried for a given amount of fuel consumed. Improvements were developed by the committee: can be achieved in two ways under an LSFC metric: (1) by improving the efficiency of the vehicle (power train, tires, • The metrics should incentivize subcomponent and total aerodynamics, etc.), the vehicle can move a given amount vehicle development. of freight with lower fuel consumption; (2) by increasing the • The metrics should relate to the transport task or ve- cargo capacity of the vehicle, the regulated party will also hicle vocation. be able to improve its fuel efficiency rating—independent • The metric should encourage energy conservation for of any change in truck subcomponent fuel efficiency. In a given task. combination these two distinct approaches will provide the • The metric should be based on energy or fuel con- greatest potential for energy conservation and savings. sumption—e.g. equivalent diesel gallons/cargo ton- Smaller-class single-unit trucks and buses have design mile. (See discussion in Chapter 2.) Normalizing to and operating characteristics that are different from larger equivalent diesel fuel permits fair comparison across vehicles. For example, utility trucks used by electric power fuel type as energy density varies with fuel type and companies may be equipped with a bucket crane and not specification. carry any substantial cargo. Clearly it would not be practi- cal to evaluate the performance of such a vehicle in terms of The committee recognized that an equipment specification the mass of transported cargo. Single-unit trucks may also regulation was an option, considering the ongoing SmartWay be placed into service towing trailers with a drawbar hitch program as an example. However, a performance-based as shown in Figure 8-2, which is common in the West and

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES which further complicates assigning an operating weight to ent cargo mass capacity and identical volumetric capacity the truck. Considering the multiplicity of factors influencing (Figure 8-3). Vehicle A has a GVW of 80,000 lb and a cargo fuel consumption and the complexity of larger vehicle sys- capacity of 48,000 lb. Vehicle B has a GVW of 97,000 lb tems and operations, the committee concludes that the notion and a cargo capacity of 61,000 lb (allowing 4,000 lb for the of a single metric being applied identically to all classes of extra axle, suspension and additional trailer structure). Both trailers have identical cargo volume capacity of 3,650 ft3. vehicles appears to be problematic. However, the committee is confident that a standard measurement protocol coupled It is clear that Vehicle A is better suited to cargo weigh- with different standards and metrics will provide a means ing 48,000 lb or less, and vehicle B is better suited to cargo of assessing fuel consumption on the basis of work task for weighing more than 48,000 lb. There is no difference in the medium- and heavy-duty vehicles. volumetric capacity of these vehicles; therefore, the cargo Class 2b and 3 vehicles tend to be higher volume general- mass dictates the vehicle choice. On the surface this case purpose vehicles with less custom built content. The high appears to be ideally suited to the vehicle mass fuel consump- production volume of this vehicle class is conducive to a tion metric (gal/ cargo ton-mile). However, when examined more general metric such as gallons per mile, gallons per more closely, it is apparent that the identical tractor would mile per person weight, or gallons per ton mile. Buses also have different fuel consumption values for each of the two have substantial variability. Of the bus categories, the long- cases given the difference in the GVW and cargo mass capac- distance motor coach not only transports passengers but they ity. It is likely that if the mass metric were applied, Vehicle B also transports freight, and therefore the task-based metric would always outperform Vehicle A (assuming that a propor- would need to consider both freight (baggage and package tionate cargo mass is used). This would be counterproductive cargo) and passenger mass. Passenger mass can be estimated for low-density, volume-limited freight applications because using “typical passenger” mass multiplied by the number of the mass metric would encourage heavier capacity vehicles available seats. Freight mass can be estimated by using a with higher tare weight. In such cases, this problem can be “typical” freight density term multiplied by the cubic capac - offset by considering an alternate metric such as gallons per cargo ft3-mile. Further discussion of alternative metrics can ity of available cargo space. be found in Annex 8-2 to this chapter. Implications of Cargo Density for Fuel Consumption METHODS FOR CERTIFICATION AND COMPLIANCE Evaluation For most truck transportation, the nature of the freight The choices of possible methods for certification and task can be classified as volume limited or mass limited. compliance of fuel consumption standards for medium and Mass-limited freight is of sufficiently high density that the heavy duty vehicles involve some of the most challenging GVW will be reached before the volumetric capacity of the regulatory design issues. vehicle is fully utilized. Volume limited freight is of suffi- One broad choice pertains to whether it would be pos- ciently low density that it occupies the available cargo space sible to establish average standards by corporate entity, as is before the GVW is achieved. It is estimated that the split done under the light duty vehicle CAFE program, or whether between volume-limited and mass-limited freight on the U.S. the breadth and diversity of the medium and heavy-duty highway network is approximately 50/50. Vehicles are often vehicle market precludes such an option. In general there designed on the basis of mass or volumetric capacity, and are important benefits associated with a corporate average the characteristics of these vehicles are somewhat sensitive standard in that it allows corporations flexibility to focus to the methods used to calculate fuel consumption. The fol- improvements on vehicle types within the retooling cycle. lowing example illustrates practical considerations that will The challenge with a corporate average standard is that the be necessary when developing a fuel consumption regulatory medium- and heavy-duty vehicle market is extremely diverse instrument. and would require establishing categories of vehicles by type Consider the real-world example of two tractor trailers and application. In addition, the light-duty vehicle CAFE having identical power units but with trailers of differ- program placed full line, largely domestic, manufacturers at Veh. “A” 80,000 lbs Veh “B” 97,000 lbs FIGURE 8-3 Identical tractors used to pull trailers of different mass capacity but identical volume capacity. Figure 8-3 Identical tractors used to pull trailers of diffe.eps bitmap

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS a competitive disadvantage due to the form of the regulatory a fuel consumption regulation for medium- and heavy-duty standard. The committee therefore strongly urges NHTSA vehicles should be to ensure that the customer has access to to proceed with caution if it considers a corporate average reliable data that are based on performance metrics related standard. Another type of regulatory flexibility is to allow to the intended function of the vehicle. manufacturers to average emissions across engine families. Approaches to characterizing or certifying heavy-duty This approach could be used to allow manufacturers to av- vehicle fuel consumption toward a standard are summarized erage fuel consumption across vehicle lines. NHTSA would in Table 8-3. The options range from testing assembled ve- need to perform a separate analysis on the market structure hicles to modeling and simulating assembled vehicles with of various truck manufacturers to understand the pros and most testing at only the power train, tires, and aerodynam- cons of setting corporate average standards within vehicle ics component levels. Any procedure must characterize the types and categories, as well as examining other regulatory consumption or efficiency using a duty cycle that is reason- flexibilities. ably representative of real use. The greater the degree of It is clear that the regulatory system should incentivize the representation, the greater will be the number of test cycles subcomponent manufacturers to make real gains in efficien- required to cover the applications, but the greater will be the cy, but this could be achieved even if the point of regulation accuracy of the process in reflecting real-world data. A high is at the OEM. The engagement of a purchaser in seeking level of fidelity between regulatory cycles and the real world highly efficient vehicles is very different from what is typi- is required to enable regulators to make the correct decisions cal in the passenger car market. One of the main thrusts of and drive the market in the desired direction. Vehicle pur- TABLE 8-3 Options for Certification of Heavy-Duty Vehicles to a Standard Method Equipment Advantages Disadvantages In-use test 400- to 600-mile test • Easy to conduct • High test-to-test variation including driver (complete course(s) on public roads • Relatively inexpensive differences, ambient conditions, and traffic vehicle) • Well-developed procedure variations • Familiar with HDV fleets • Best for comparing one truck to another • SAE procedures • Requires the use of a “reference truck” to limit test- to-test variability Test track Closed, 1- to 5-mile oval or • Easy to conduct • Facilities are limited and expensive (complete circular test track • Good repeatability • Complexity of test cycles limited vehicle) • Best for high-speed steady-state test cycles • Cannot incorporate changes in grade to test cycle • Affected by ambient conditions • Requires “reference truck” to reduce test-to-test variability Chassis Heavy-duty chassis • Well-developed procedure • Facilities are limited and expensive dynamometer dynamometer with data • Computerized drivers’ aids ensure very good • Accuracy depends on accurate input data from from a coast-down test compliance with transient test cycles coast-down test track • Very good repeatability • Coast-down data not reliable • Inability to handle variable grade Engine test Engine dynamometer • Well-developed test • Accuracy depends on complexity of simulation plus vehicle Vehicle simulation model • Minimal additional burden model and “accuracy” of model inputs simulation • Lowest total cost to vehicle manufacturers • Development of vehicle-specific modeling modeling • Ability to run large number of vehicle test cycles parameters likely to require additional vehicle/ off a single engine test component testing (i.e., dynamic wind tunnel tests for aerodynamic drag, tire tests) Power train Engine dynamometer that • Builds on current practice of engine • New business model may be needed to integrate test plus will accommodate hybrid dynamometer tests engine and other power train components vehicle power train hardware and • Ability to accommodate many cycles and • Process development required for integration of simulation model/cycle control (CIL) vehicles via models simulation into regulatory framework (see above). modeling Vehicle simulation model • Facilitates harmonization with pollutant emission certification Simulation Vehicle simulation model • Ability to accommodate many cycles and • Still requires substantial testing for model of entire vehicles via models development and validation vehicle • Models not adequate to cover regulated pollutants, so emissions test still required SOURCE: Modified from Bradley and Associates (2009).

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES chasers require an even higher level of fidelity to make the are often used in ways similar to light duty vehicles, and ex- best decisions when specifying a new vehicle. Sophisticated isting test facilities could be used. Many of these vehicles are larger fleets will often change engine, transmission, tire, or also made in relatively high volume, making a full-vehicle even OEM selection to gain a 1 or 2 percent fuel consump- test less difficult to manage for the manufacturer. An ability tion reduction. Achieving this level of fidelity is a major to rely on existing industry and regulator experience and challenge. capability makes this approach attractive. As discussed previously, using the results from existing In medium- and heavy-duty vehicles from Class 3 up engine dynamometer testing for heavy-duty vehicles would through Class 8a, manufacturing volumes are often low and allow for accurate, repeatable comparisons, but there are many different configurations are built on a given platform. substantial drawbacks to limiting the scope of the rule to only This makes chassis dynamometer fuel consumption testing engine technologies. For example, there is a potential lack of much more difficult and expensive than in smaller vehicles. fidelity between the dynamometer test cycle and real world For these larger vehicles it makes sense to combine engine performance. Table 8-3 describes the four major widely used or power train test data with vehicle simulation models. test methods—in-use testing, test track testing, chassis dy- Particularly in the case of hybrid vehicles, it will be im- namometer testing, and simulation modeling—and identifies portant to have high-fidelity data for the fuel consumption the advantages and disadvantages of each approach. A final and performance of the power train. This data may come method, generally used in power train development to test the from testing, simulation, or a blend of simulation such as combined engine and drive train, would require the engine hardware-in-the-loop (HIL) or CIL. Even if a pure simula- dynamometer test cycle to utilize the load characteristics tion approach is used, some level of test data is required to of real trucks over real duty cycles. The load on the engine validate the models. A wide range of vehicle duty cycles may would be determined by a vehicle simulation, an approach need to be simulated or tested in order to achieve adequate that bears some similarity to the approach used in Japanese fidelity with real-world fuel consumption data. regulations. The truck and trailer simulation (aerodynamics, Tractor trailers (Class 8b) are also available in dozens of tires, mass) could include applicable fuel-saving features to configurations, many of which are produced in low volume. represent a range of truck models, unlike the fixed truck char- Once again, chassis dynamometer fuel consumption test- acteristics defined in Japan’s model. To carry this concept to ing would be difficult and expensive, and so some level of hybrid vehicles, the “engine” would need to be augmented vehicle simulation modeling is likely to be required. Engine with the hybrid components and thus become a “power train” or power train test data can be provided as needed. Again, in the test cell (also called component in the loop; CIL). As many vehicle duty cycles may need to be simulated or tested the interaction between engines and conventional (nonhy- in order to achieve adequate fidelity. Regulators will want to brid) transmissions becomes increasingly emphasized, the reinforce rather than impede the fuel consumption sensitivity concept of evaluating the performance of a complete power in Class 8b, where purchasing decisions are often based on train retains merit. differences as small as 1 or 2 percent in fuel consumption. Three of the methods listed in Table 8-3 for determining For example, a buyer will want to know which of 10 or more vehicle fuel consumption require the use of complete vehi- available aerodynamic treatments will perform best in the cles: in-use testing, test track testing, and chassis dynamom- buyer’s particular application. Defining tests or simulations eter testing. Vehicles that operate with trailers would need that can provide an accurate answer to a question like this to have standard trailers for the testing. In the case of Class will not be easy. Defining a regulatory process and standards 8b vehicles, at least two trailer types would be required: a that do not drive incorrect decisions by vehicle manufactur- standard box van trailer to be tested on tractors intended for ers will require considerable care. this type of application, and a low frontal area trailer for For the first iteration of the new regulatory program for trucks to be used with other trailer types. medium- and heavy-duty vehicles, the committee recom- Two of the methods for determining vehicle fuel consump- mends that regulators consider test methods that minimize tion that are listed in Table 8-3 require only component-level the administrative burden on those vocational vehicles that testing. These are the engine test plus vehicle simulation ap- are not the large fuel users (that is, all vehicles not included proach, and the power train test plus vehicle simulation. The in Class 2b, Class 6, or Class 8b line-haul tractor trailers). final method listed in Table 8-3 is pure simulation, although For these numerous types of vehicles that account for less even this approach will require some testing to validate the than 10 percent of commercial truck fuel consumption, the data used in the simulation model. committee recommends two options: (1) pure vehicle simu- lation, and (2) engine-in-the-loop, also called CIL (engine connected to a dynamometer that emulates the rest of the Sample Applications of Methods to Vehicle Classes vehicle). The pure simulation modeling approach allows the For Class 2b vehicles and Class 3 pickup trucks, a chassis regulated entity to piggyback off of existing engine tests and dynamometer test for fuel consumption similar to the test data for other components (e.g., transmission, tires, electric used in light-duty vehicles is a viable option. These vehicles machine). The CIL approach takes advantage of the exist-

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS ing engine test procedure while also incorporating existing The choice of test cycle is a critical part of any vehicle component data. At this point, it appears that pure simulation fuel consumption test or simulation. Test cycles selected for would be the less expensive option. regulatory use will need to reflect real-world duty cycles When simulation models are used, inputs are required to to the extent possible. Parameters of importance include represent components. Some of these inputs may come from maximum speed, average speed, speed fluctuation, number standardized tests, such as a test for tire rolling resistance or a of stops, and amount of idling. It will not be possible to faith- wind tunnel test for aerodynamic drag. These inputs may also fully reproduce the duty cycle to be experienced by every come from simulation models, if the models are validated vehicle, so similar applications will be represented by one and sufficiently accurate. For example, a CFD model may be or a few duty cycles for regulatory purposes. used to determine the Cd of a vehicle in place of wind tunnel testing. Data used in a model for regulatory approaches will Overall Regulatory Structure need to come from a standard test or analysis process that is recognized by the entire industry. Many new test and analy- Introduction sis procedure standards will be needed. It may be necessary to approve both codes and experimental facilities to insure Applying a regulatory system that pushes technology quality control and uniformity in the determination of wind in the drive train, tires, and vehicle shape (aerodynamics) drag. ensures that incentives are applied at the foundation of the Figure 8-4 shows an outline of how a power train test can major vehicle systems that influence fuel consumption. be combined with a vehicle simulation model to determine Given the high fuel consumption sensitivity of some me- the fuel consumption of a vehicle. This is the CIL approach. dium- and heavy-duty vehicle purchasers, it appears that one This figure shows a hybrid electric power train with a diesel priority should be to ensure that accurate information on the engine including exhaust aftertreatment. The power train is fuel consumption characteristics of a completed vehicle is tested in a test cell, where the dynamometer load is deter- available to the purchaser. Having such information would mined by a vehicle model. The vehicle model, in turn, uses help drive the selection of vehicles with the lowest fuel con- input data for parameters such as rolling resistance, mass, sumption for the task performed. The notion of regulating and aerodynamic drag. The vehicle model is exercised over a the final-stage manufacturer and including a requirement on specified route, and the resulting power demands are applied the component manufacturers to provide relevant perfor- on the power train by the dynamometer. The resulting fuel mance data to the purchaser will be an important part of the consumption is experimentally measured. regulation. FIGURE 8-4 CIL test of a hybrid vehicle power train to determine vehicle fuel consumption on a specific test route. Figure 8-4 CIL test of a hybrid vehicle powertrain to determ.eps bitmap--legibility is degraded

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES Focusing on the power train, aerodynamics, and tires to fix issues that are found. There are numerous technical provides a means of incentivizing these three important ar- challenges related to implementation of this program (e.g., eas. Measuring and documenting the performance of these reliable and accurate methods to determine tire rolling key components in a constant and transparent way will be resistance and vehicle aerodynamic drag coefficients, incor- important for the final-stage manufacturer. NHTSA may poration of simulation modeling with hardware, integrating wish to require suppliers to provide information in standard- a hybrid drive train within the standard test cell, character- ized form at the power train, aerodynamics and tire levels. izing subcomponents for use in simulation modeling). This The final-stage manufacturer would have the responsibly of trial period will serve as a means for developing and refining combining the performance of these components to achieve the regulatory processes before the official start date of the the lowest cost for the intended vehicle task while comply- program. ing with the regulatory fuel consumption requirement. The A second element would include gathering data on fuel task-based fuel consumption metrics would be used by the economy from several representative fleets of commercial final stage manufacturer to inform the customer as part of a trucks (e.g., long-haul, delivery vans, specialty vehicles, and labeling requirement. large pickups). These data would continue to be collected In summary, the concept of this example regulatory model once the program was established in order to provide a real is as follows: world check on the effectiveness of the regulatory design on the fuel economy of trucking fleets in various parts of the 1. Major components such as power train, tires, and marketplace and in various regions of the country. As this aerodynamics (including factors for accessories and program will place an additional administrative burden on auxiliaries) would each be tested or simulated, and NHTSA and private operators, the committee recommends efficiency data made available to OEMs in a common that Congress consider an annual funding allocation for this format using industry standard metrics and proce- program. dures. 2. The completed vehicle would be regulated, and in ad- Concluding Comments dition customer specific data would be provided that would inform the vehicle purchaser about the fuel This is an important juncture. The choices that will be consumption performance of the particular vehicle in made over the course of the next few years will establish the relation to the intended task. This form of regulation regulatory design for medium- and heavy-duty-vehicle fuel would simplify the regulatory task compared to other consumption standards for the next several decades at least. alternatives and provide the flexibility needed to ad- Although the stringency of the standards themselves may be dress the complex nature of the industry. revisited from time to time, the regulatory design elements (regulated parties, certification tests and procedures, compli - ance methods)—once established—are far more difficult to Compliance, Audit, Enforcement modify. Chapter 3 describes the compliance audit process for In many cases the commercial vehicle market is sophis- heavy-duty engines and for passenger car emissions. The ticated, driven by knowledgeable purchasers who focus on committee believes that similar methods would be adequate the efficiency of their operations, including the fuel costs to audit compliance for heavy-duty vehicle fuel consump- associated with accomplishing their tasks. Thus, one of the tion. The use of models and simulation in the certification most important challenges facing NHTSA is how to enhance process could cause a complication in auditing in that the and improve upon the commercial truck industry’s exist- audit test on a real vehicle might need to be assessed against a ing incentive to maximize fuel economy of its trucks and model output generated for certification. This concern would fleets. need to be addressed in the design of the regulation. At the same time, there are commonly acknowledged characteristics in the commercial marketplace for trucks and buses that may be improved by a regulatory approach, such Pilot Program as split incentives between owners and operators (e.g., trail- The committee recommends that NHTSA conduct a pilot ers), and the short payback period of 18 months to 2 years, program to “test drive” the certification process and validate that create barriers to the adoption of efficiency technologies the regulatory instrument proof of concept. There are two for many purchasers. The existence of technology packages broad purposes for such a pilot program. In the first element, for some vehicle classes that offer significant fuel consump- the agency would gain experience with certification testing, tion reduction potential at reasonable costs suggests that data gathering, compiling, and reporting. There needs to be a well-designed policies to overcome problems such as split concerted effort to determine the accuracy and repeatability incentives or too short a payback period may yield important of all test methods and simulation strategies that will be used benefits (see Table 6-19). with any proposed regulatory standards and a willingness Due to the complexity of the vehicle market the commit-

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS tee was not able to give adequate consideration to the non- benefit from improvements in aerodynamics and tires (see commercial markets such as personal pickup trucks, school Chapter 5 for details). buses, personal motor homes. NHTSA should consider these Recommendation 8-1. When NHTSA regulates, it should applications in their regulatory proposal. A fundamental concern raised by the committee and those regulate the final-stage vehicle manufacturers since they have who testified during our public sessions was the tension be- the greatest control over the design of the vehicle and its tween the need to set a uniform test cycle for regulatory pur- major subsystems that affect fuel consumption. Component poses, and existing industry practices of seeking to minimize manufacturers will have to provide consistent component the fuel consumption of medium and heavy-duty vehicles performance data. As the components are generally tested at designed for specific routes that may include grades, loads, this time, there is a need for a standardized test protocol and work tasks or speeds inconsistent with the regulatory test safeguards for the confidentiality of the data and information. cycle. This highlights the critical importance of achieving It may be necessary for the vehicle manufacturers to provide fidelity between certification values and real-world results the same level of data to the tier suppliers of the engines, to avoid decisions that hurt rather than help real-world fuel transmissions, and after-treatment and hybrid systems. consumption. Recommendation 8-2. Separate regulation of trailer manu- Because regulations can lead to unintended consequenc - es, either because the variability of tasks within a vehicle facturers will be necessary to promote more fuel-efficient class is not adequately dealt with or because regulations trailers, including integration of the trailer design with the may lead to distortions between classes in the costs of ac- tractor for improved aerodynamic performance, lower tare complishing similar tasks, the committee urges NHTSA to weight, and a requirement for low-rolling-resistance tires. carefully consider all factors when developing its regulatory proposal. Fuel Consumption Performance Metrics Finding 8-4. Since the primary social benefit of the me- FINDINGS AND RECOMMENDATIONS dium- and heavy-vehicle sector is the efficient and reliable movement of freight, movement of purpose-built integrated Regulated Vehicle Types equipment, or performance of a task, it is necessary to estab- Finding 8-1. While it may seem expedient to focus initially lish a metric that includes a factor for the work performed on those classes of vehicles with the largest fuel consumption (e.g., gallons per cargo ton-mile rather than simply gallons (i.e., Class 8, Class 6, and Class 2b, which together account per mile) to ensure that the regulatory instrument meets for approximately 90 percent of fuel consumption of me- societal goals. dium- and heavy-duty vehicles), the committee believes that Finding 8-5. Choosing a metric associated with the move- selectively regulating only certain vehicle classes would lead to very serious unintended consequences and would com- ment of freight will promote improvements that increase promise the intent of the regulation. Within vehicle classes, the amount of cargo that can be carried per unit of fuel con- there may be certain subclasses of vehicles (e.g., fire trucks) sumed, and thus provide a means of quantifying the benefits that could be exempt from the regulation without creating of more productive vehicles that move the same amount of market distortions. freight with fewer trips and fewer vehicle-miles traveled, such as longer combination vehicles (LCVs). Regulated Parties Finding 8-6. Setting a metric based exclusively on gallons Finding 8-2. Large OEMs, which have significant engi- per cargo ton-mile (gal/ton-mile) may not adequately address neering capability, design and manufacture almost all Class light-density freight that is limited by volume. 2b, 3, and 8b vehicles. Small companies with limited engi - Recommendation 8-3. NHTSA should establish fuel con- neering resources make a significant percentage of vehicles in Classes 4 through 8a, although in many cases they buy sumption metrics tied to the task associated with a particular the complete chassis from larger OEMs. Regulators will type of medium- or heavy-duty vehicle and set targets based need to take the limitations of these smaller companies on potential improvements in vehicle efficiency and ve- into account. hicle or trailer changes to increase cargo-carrying capacity. NHTSA should determine whether a system of standards for Finding 8-3. Commercial trailers are produced by a separate full but lightly loaded (cubed-out) vehicles can be developed group of about 12 major manufacturers that are not associ- using only the LSFC metric or whether these vehicles need a ated with truck manufacturers. Trailers, which present an different metric to properly measure fuel efficiency without important opportunity for fuel consumption reduction, can compromising the design of the vehicles.

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0 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES Methods for Certification and Compliance However, by knowing the effects of the performance of major subcomponents on fuel consumption, it may be practical to Finding 8-7. The regulatory certification and compliance demonstrate compliance certification with vehicle standards options discussed in this report are the product of much by aggregating the subcomponents into a specified virtual discussion and thought by committee members, supported vehicle for computers to evaluate fuel consumption of the by input from industry, government, and other organizations. completed vehicle. Some certification and compliance methods seem more practical than others, and the committee acknowledges that Finding 8-12. Further research will be required to underpin there may be other options or variations that have yet to be the protocol used to measure key input parameters, such as identified. Nevertheless, the committee has determined that tire rolling resistance and aerodynamic drag forces and to en- regulating the total vehicle fuel consumption of medium- sure the robustness of simulations for evaluating vehicle fuel and heavy-duty vehicles will be a formidable task due to the consumption. These major components may be assembled complexity of the fleet, the various work tasks performed, through simulation to represent a whole-vehicle system, and and the variations in fuel-consumption-related technologies models benchmarked to reliable data may be used to extend within given classes, including vehicles of the same model the prediction to a variety of vehicle types, by changing and manufacturer. bodies (aerodynamic measures), tires, and operating weights associated with the power trains. Finding 8-8. A certification test method must be highly accurate, repeatable, and identical to the in-use compliance Recommendation 8-4. Simulation modeling should be used tests as is the case with current regulation of light-duty ve- with component test data and additional tested inputs from hicles tested on a chassis dynamometer, and for heavy-duty power train tests, which could lower the cost and adminis- engine emission standards tested on engine dynamometers. trative burden yet achieve the needed accuracy of results. This is similar to the approach taken in Japan, but with the Finding 8-9. Using the process and results from existing important clarification that the program would represent all engine dynamometer testing for criteria emissions to cer- of the parameters of the vehicle (power train, aerodynamics tify fuel economy standards for medium- and heavy-duty and tires) and relate fuel consumption to the vehicle task. vehicles would build on proven, accurate, and repeatable Further, the combined vehicle simulation/component testing methods and put less additional administrative burden on the approach should be supplemented with tests of complete industry. However, to account for the fuel consumption ben- vehicles for audit purposes. efits of hybrid power trains and transmission technology, the present engine-only tests for emissions certification will need Finding 8-13. There is an immediate need to take the to be augmented with other power train components added findings and recommendations in this report and begin the to the engine test cell, either as real hardware or as simulated development of a regulatory approach. Significant engineer- components. Similarly, the vehicle attributes (aerodynam- ing work is needed to produce an approach that results in ics, tires, mass) will need to be accounted for, one approach fuel efficiency standards that are cost-effective and that ac- being to use vehicle-specific prescribed loads (via models) curately represent the effects of fuel-consumption-reducing in the test cycle. This will require close cooperation among technologies. The regulations should fit into the engineering component manufacturers and vehicle manufacturers. and development cycle of the industry and provide meaning- ful data to vehicle purchasers. Finding 8-10. At present there is no established federal test method for heavy-duty vehicle fuel consumption. Empirical Recommendation 8-5. Congress should appropriate money testing (from components in an emulated vehicle environ- for and NHTSA should implement as soon as possible a ment to the whole vehicle), simulation modeling, or both major engineering contract that would analyze several ac- may be used for the characterization and certification of tual vehicles covering several applications and develop an regulated equipment. Each approach involves uncertainties approach to component testing and related data collection that can affect certification and compliance. This finding in conjunction with vehicle simulation modeling to arrive at underscores the need for a pilot regulation program. LSFC data for these vehicles. The actual vehicles should also be tested by appropriate full-scale test procedures to confirm Finding 8-11. Significant segments of the medium- and the actual LSFC values and the reductions measured with heavy-duty-vehicle purchasing process are highly consumer fuel consumption reduction technologies in order to validate driven, with many engine, transmission, and drive axle the evaluation method. choice combinations resulting in a wide array of completed vehicles for a given vehicle model. From a regulatory stand- Recommendation 8-6. NHTSA should conduct a pilot point, the use of expensive and time-consuming chassis program to “test drive” the certification process and validate testing on each distinct vehicle variation is impractical.

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS the regulatory instrument proof of concept. It should have Davis, S., S. Diegel, and R.G. Boundy. 2009. Transportation Energy Data Book, Edition 28. Rept. No. ORNL-6984. Knoxville, Tenn.: U.S. De - the following elements. partment of Energy, Energy Efficiency and Renewable Energy. DOC (U.S Department of Commerce), Census Bureau. 2005. 2002 Eco- 1. Gain experience with certification testing, data gath- nomic Census, Industry Product Analysis. March. Washington, D.C. ering, compiling, and reporting. There needs to be a DOE, EIA (U.S. Department of Energy, Energy Information Administra - concerted effort to determine the accuracy and repeat- tion). 2009a. Annual Energy Review 2008. DOE/EIA-0384(2008). Washington, D.C.: EIA. ability of all the test methods and simulation strategies DOE, EIA. 2009b. Annual Energy Outlook 2009. DOE/EIA-DOE/EIA- that will be used with any proposed regulatory stan- 0383(2009). March. Washington, D.C.: EIA. dards and a willingness to fix issues that are found. Federal Highway Administration, Highway Statistics Summary to 1995, 2. Gather data on fuel consumption from several repre- Table VM-201A and Highway Statistics (annual releases), Table VM-1. sentative fleets of vehicles. This should continue to Washington D.C. NESCCAF, ICCT, SwRI. 2009. Regulation of Heavy-Duty Vehicle Fuel provide a real-world check on the effectiveness of the Economy and GHG Emissions: Issues and Opportunities. October. regulatory design on the fuel consumption of trucking Available at www.nescaum.org/.../heavy-duty-truck-ghg_report_final- fleets in various parts of the marketplace and various 200910.pdf. regions of the country. TIAX, LLC. 2009. Assessment of Fuel Economy Technologies for Me - dium- and Heavy- Duty Vehicles. Final Report. Report to the National Academy of Sciences. Cambridge, Mass. September. BIBLIOGRAPHY Bradley, M.J. and Associates LLC. 2009. Setting the Stage for Regulation of Heavy-Duty Vehicle Fuel Economy and GHG Emissions: Issues and Opportunities. Washington D.C.: International Council on Clean Transportation. February.

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES ANNEX 8-1: the other hand, a simulation proves economical in modeling COMPONENT-BASED FUEL CONSUMPTION the effect changes in controls or architecture, or in examin- ASSESSMENT METHOD ing different trucks employing some similar components, since these changes would otherwise necessitate a large Introduction number of tests of a whole component or major component subsystem. The objective of this annex is to present, in broad terms, The accepted methods used to measure rolling resistance an example of a credible methodology for characterizing of wheels (with tires), the efficiency of a power train, and the fuel consumption of a medium- or heavy-duty vehicle the drag characteristics of a body all differ substantially. by tests and/or simulation of the major components. This The existing test methods may need further development to concept considers a certification and labeling approach for achieve fidelity with real world vehicle operating results. the main fuel consumption components that would be ag- gregated to provide fuel consumption performance of the • Tire rolling resistance is determined independently and completed vehicle. This approach recognizes that many fuel physically in accordance with accepted test protocol. consumption improvements occur at the sub component Power train performance is determined physically level and provides a means of quantifying the performance either by attaching a power train to a dynamometer or of these components so that the final stage manufacturer will by operating a chassis or mule containing a power train have reliable performance data to determine vehicle fuel with wheels on the drive axle on a chassis dynamom- consumption. eter: in the latter case the wheels and dynamometer For advanced heavy-duty vehicle designs, the physical rollers are merely connection components between the power train is not readily classed into separately operating power train and a rotating dynamometer. Aerodynamic sub-components such as engine and transmission, because body performance is determined in a wind tunnel. there can be a high level of communication between these These three test approaches are substantially different sub-components and because they are mutually controlled to and independent from one another, and employ differ- achieve their function. For example, an engine and a hybrid ent apparatus. drive train are inseparable in operation because the control • An admixture of these characterizations may be ob- system commands both major subcomponents to achieve tained through the coast down of a whole vehicle on propulsion. Even with the lowest technology option of a the road, but the metrics required are intertwined and manual transmission attached via a clutch to an engine, the the accuracy of the process is challenged by surface average human driver determines the engine operating enve- and atmospheric effects. lope based on the duty cycle, the engine performance map, • Tire rolling resistance may be simulated through the transmission ratios and the drive axle ratio. The realistic computer-aided finite element design models rely- engine operating envelope is not defined uniquely without ing on fundamental materials stress and deformation these sub-components attached and in use. With some equations. Power train performance may be simulated qualification, present day engine testing may not necessarily by using models currently available for whole vehicle reflect how the engine will be used in a specific application simulation, by assembling accurate sub-models of insofar as the torques and speeds of the engine in use, and sub-components with links that rely on basic phys- the nature of transients in use may not reflect the torques, ics (torques and speeds) or precisely defined control speeds and transients employed in the test cell. algorithms. Aerodynamic body performance may de- If simulation and physical testing are equally verifiable termined using finite element fluid flow models which as facsimiles of the real-world operation of a vehicle, its may vary in their level of empirical tuning. These three components or its sub-components, then simulation and modeling processes are substantially different from physical testing should be equally valid techniques for use one another, and employ different types of code for in certification. For example, aerodynamic drag on a body their execution. may be found either by wind-tunnel testing or by computer- aided aerodynamic modeling, provided both methods can be The Component-Based Procedure shown to be accurate and repeatable. As a further example, the performance characterization of an engine and intelligent The terms “measured” and “measurement” below are in- transmission combination may be found using a dynamom- tended to reflect either output from testing activities or output eter in a test cell, or by fully characterizing the engine and from modeling or simulation activities, with no preference transmission separately and combining them with a model for either, but with the assertion that either approach requires for their controller through a simulation exercise. On the verified fidelity with regard to accuracy and precision. one hand, when simulation is used, each component in the The three components, namely body, power train and simulation must be fully characterized, usually necessitating wheels (with tires), of a vehicle proposed for sale should be a larger number of measurements of subcomponents. On measured separately. Certain accessories may also require

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS Vehicle independent measurement if they are not easily included in the other three. Different vehicle types, categorized by weight class and use, may each be associated with one or more drive cycles, Wheels (Including Tires) reasonably corresponding to real use of those vehicles. For example, an over-the-road tractor may be associated with The wheels of a vehicle are usually characterized with a high-speed cycle, indicative of freeway behavior, and respect to rolling resistance. The rolling resistance, as a coef- a low-speed cycle, indicative of transient behavior in an ficient, represents the horizontal force which must be applied urban environment. Consider that the efficiency of a power to overcome the internal energy losses of the tire when it train is to be measured or modeled, and that its associated supports a given vertical weight on a horizontal surface. The application, body and wheels are all defined. These drive coefficient of rolling resistance (Crr) is reasonably constant cycles exemplifying the application can be translated to a with respect to speed and vertical load. The rolling resistance set of hub speed (versus time) and hub torque (versus time) is influenced largely by the tire material construction, wear, target values, provided that the power train is considered to and to a lesser degree the road surface. be propelling this well-defined vehicle. Data which are re- quired to formulate a power train test (physical or simulated) Aerodynamics are largely the same as those required to execute a light-duty vehicle chassis test and are as follows: The aerodynamics of the vehicle should be determined by installing a body on a suitable facsimile of wheels and • Vehicle mass chassis in a wind tunnel, or else by installing a whole vehicle • Tire rolling diameter in a wind tunnel. A scaled model may be used where it can • Effective Crr value for the wheels be demonstrated by similarity analysis that the resulting • Effective CdA value or the aerodynamic drag measurements may be applied to a full scale measurement. • Value for air density The measurement of interest is the drag force on the body • Test cycle, as a set of speed versus time values as a function of wind speed over the body. Drag force var- ies in close proportion to the square of the air speed, and is The power train should then be exercised through the influenced by air density and by yaw (which results in real speed-torque target values either physically in a test cell or vehicle operation from the presence of wind which is not in through simulation. A human driver will be needed, although the direction of travel and which is not very low in speed physical testing and simulation may otherwise employ a with respect to the vehicle speed.) Computer simulation of driving algorithm, provided that the algorithm reasonably air flow over the body may be used to infer the drag force, represents a human driver. The choice of driver or driving provided appropriate controls are used. algorithm must be addressed carefully, because it may impact Certain trucks and tractors simply would not benefit from engine transient behavior and manual transmission behavior some aerodynamic accouterments, either because they are substantially. For rapid decelerations, it will be necessary not intended to be driven at high speed, or because they do to use friction brakes or a retarder to provide deceleration not carry a box body or tow a box trailer with a large frontal torque, and for hybrid vehicles the decelerations may be used area. For vehicles which are not intended to be driven at high for energy capture. A physical power train test may also be speed, determination of CdA would be purposeless. accomplished with a mule or complete vehicle on a chassis dynamometer, but the dynamometer coefficients measured or Power Train projected at the drive hubs must be set to reflect the values of Crr and CdA required for the designated power train test, The power train of the vehicle consists typically of an and not necessarily for the vehicle on which the test is being engine, a transmission, which may include hybrid hydraulic performed. or hybrid electric components, one or more drive axles, pos- sibly an energy storage system, and a control system to man- Assembled Components age the components in response to driver commands under constraint of road load. The exhaust aftertreatment system, The tires, aerodynamics and power train might all be often considered part of the engine, may evolve to the status separately regulated. However, they might also be combined of a separate component in future versions of testing. to mimic a completed vehicle. Experimentally, a power train A power train may be used with a variety of tires and test will provide whole vehicle fuel consumption data if the bodies in real vehicle applications, and may be configured power train test uses values for aerodynamic drag and for tire or optimized differently for each application, or configured rolling resistance which represent that vehicle. However, it is generically for use in several applications. inappropriate to expect that each variant of a vehicle should require a separate power train test. If modeling is used in a

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES verifiable fashion to mimic the power train and provide ef- variation of fuel consumed with respect to average speed can ficiency data for a specific vehicle, then the same model may be computed, and these data would be available for consumer be modified with reasonable confidence to accommodate information and as regulatory metrics. As feedback controls varying values for aerodynamic drag, rolling resistance, and become common, power trains will use many sensor inputs vehicle weight. In this way, a wide variety of vehicles which to ride up against NTE (Not to Exceed) limits for NOx. This use the same power train may be simulated economically. means that actual fuel consumption may vary significantly For any particular power train configuration, the power as a function of ambient temperature, humidity, intake mani- train performance may be confirmed on two or three cycles fold temperature, coolant and oil temperatures, barometric using weight, aerodynamic drag and tire rolling resistance pressure, aftertreatment temperature, aftertreatment aging, suited to a reasonable vehicle type. Data of this kind may be and other factors. Some reasonable consensus on standard extended through modeling to reveal the power train perfor- test conditions will be important for reporting against a fuel mance for any test cycle. If several cycles are executed, the consumption standard.

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 APPROACHES TO FUEL ECONOMY AND REGULATIONS ANNEX 8-2: chassis. For the purpose of this discussion it is assumed that ALTERNATIVE METRICS the flat bed unit is used for heavy loads such as steel or lum- ber and the box truck is used for lighter density cargo such The measures listed in Table 8-3 address the vehicle task as courier packages. If the mass metric (gal/cargo ton-mile) and are based on fuel or energy consumption. This list is not were used then there would be strong incentive to minimize complete as there are many vehicle tasks not covered. This vehicle tare weight so that the cargo mass term in the metric annex elaborates on some of these tasks. could be increased thereby improving performance. This One alternative approach to regulating tractor trailer fuel would have a clear benefit for the flat bed truck as the cargo consumption would be to simply regulate the tractor based is of sufficient density to benefit from the lighter vehicle. on standard loads tied to engine power rating. Tractors could However for the box truck with low density cargo, the in- be grouped into power ranges such as low-, medium-, and centive for reduced tare weight may not provide any direct high-horsepower categories, and corresponding GVW values benefit to the shipper. In addition, when the mass metric is applied. Each of these power categories would have separate applied to the box truck, it would give preference to a lighter fuel consumption targets. See Figure 8-2-1. smaller box which would undermine the volumetric value of Consider the single vehicle units shown in Figure 8-2-2 the vehicle. A metric based on volume (gal/cargo ft3-mile) with the same GVW rating and the identical power train and would resolve this particular application.

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 TECHNOLOGIES AND APPROACHES TO REDUCING THE FUEL CONSUMPTION OF MEDIUM- AND HEAVY-DUTY VEHICLES FIGURE 8-2-1 Options for performance metrics. Figure 8-A-1 Option of performance metrics.eps 2 bitmaps FIGURE 8-2-2 Identical GVW rated straight trucks for high- and low-density commodities. Figure 8-A-2 Identical GVW rated straight trucks for high an.eps bitmap