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NRC report offers guidance on development of Phase 2 rules to reduce fuel consumption and GHG from medium-and heavy-duty vehicles; more natural gas and aerodyanamics, expanded lifecycle considerations

Expanding the use of natural gas as a transportation fuel and greater use of aerodynamic devices on trailers are among the 17 overarching strategies recommended by a new National Research Council report for reducing fuel consumption by tractor-trailers, transit buses, commercial vehicles, trucks, and other medium- and heavy-duty vehicles (MHDVs).

The report follows a 2010 Research Council report the findings and recommendations of which informed the “Phase I Rule” on fuel consumption and greenhouse gas emissions of medium- and heavy-duty vehicles issued jointly by the National Highway Traffic Safety Administration and US Environmental Protection Agency. (Earlier post.) The new report offers guidance for the “Phase II Rule” under development, which is directed at technologies and programs in the post-2018 time frame. (Earlier post.) The committee will expand upon this new work and issue a final report in 2016 that will cover a broader range of technologies and approaches that address the 2025-2030 time frame.

In the present report, the committee seeks to advise NTHSA as it revises its regulatory regime for MHDVs that meet the two agencies’ objectives of: (1) reducing in-use emissions of carbon dioxide from MHDVs; (2) reducing in-use emissions of other greenhouse gases (GHGs) from MHDVs; and (3) improving in-use efficiency of fuel use in MHDVs—by driving innovation, advancement, adoption and in-use balance of technology through regulation. At the same time, we seek to advise on pathways to accomplish this subject to the following constraints: (a) holding life-cycle cost of technology change or technology addition to an acceptable level; (b) holding capital cost of acquiring required new technology to an acceptable level; (c) acknowledging the importance of employing a balance of energy resources that offers national security; (d) avoiding near-term, precipitous regulatory changes that are disruptive to commercial planning; (e) insuring that the vehicles offered for sale remain suited to their intended purposes and meet user requirements; (f) ensuring that the process used to demonstrate compliance is accurate, efficient and not excessively burdensome; and (g) not eroding control of criteria pollutants or unregulated species that may have health effects.

Objectives 1, 2, and 3 are not fully congruent when fuels having different carbon content are considered, and when GHGs other than carbon dioxide are considered. In particular, GHG and efficiency are decoupled when the fuel and engine technology changes. Objectives 1, 2 and 3 also require that any regulation must reflect real-world activity and performance of vehicles. Constraints (a) and (b) suggest that the regulation and standards may stop short of driving best available technology or certain technology pathways. However, (a) and (b) do not go so far as to suggest that new technology must offer a positive return on investment for the consumer through reduced fuel usage: needs for efficiency and GHG reduction may reach beyond economic drivers for change. Constraints (c), (d) and (e) may dictate that a single standard may not be reasonable because a mix of fuels may be needed and because these different fuels may not be capable of meeting a common standard if the standard is set too ambitiously. Constraint (f) may be in conflict with the real-world benefit implications of the objectives. Constraints (c) and (d) imply that the regulations should not close current or anticipated technology pathways without adequate notice to manufacturers and suppliers.

—Phase Two First Report

Among the new engine and vehicle technologies introduced since the Phase I Rule, the emergence of natural gas as a transportation fuel is significant, the report says. Due to lower carbon content, the greenhouse gas emissions of natural gas are lower than for gasoline or diesel fuel, but this benefit is partially negated by the lower efficiency in currently available engines and may be offset by the increased greenhouse gas effects of methane. In addition, the natural gas fueling infrastructure is underdeveloped and will require large investments to provide enough stations to prevent disruption in routes and travel times for longer-haul trucks.

In light of these trade-offs, the report recommends that NHTSA and EPA develop a separate standard for natural gas vehicles as is presently the case for diesel- and gasoline-fueled vehicles. Factors the agencies should consider in setting the standard include the maximum feasible ability of natural gas engines to achieve reductions in GHG emissions and fuel consumption, the uncertainties involved with the various alternatives, the impact of duty cycles on the ability to comply with the vehicle standards, the cost of the technology, and rapid growth of the market for natural gas engines and vehicles. This may require additional focused studies.

Because current estimates vary significantly regarding quantification of emissions leakage of methane, the report also recommends that the agencies should begin to consider the “well-to-tank” energy consumption and greenhouse gas emissions associated with natural gas vehicles as well as for other vehicle and energy technologies that include biofuels, dimethyl ether, and hydrogen fuel cells. EPA and NHTSA should assemble a best estimate of well-to-tank GHG emissions to be used as a context for developing future rulemakings.

Due to the economics-driven rapid adoption of natural gas, there is urgency to develop an optimum solution in Phase II Rule standards for both GHG emissions and fuel consumption (as well as criteria emissions) that will accommodate this fuel without artificially disrupting prevailing commercial transportation business models, the report said. As a specific example, the Greenhouse gas Emission Model (GEM) certification tools need to include natural gas engine maps to more accurately quantify the emissions and fuel economy of natural gas vehicles.

The committee that wrote the report found that the majority of both new and in-use van trailers currently do not use fuel-saving aerodynamic devices. Use of these devices, in particular side skirts, provides a full return on investment through fuel savings in about one year, on average. However, when a trailer is not owned by the tractor owner/operator (who pays for fuel), there is no incentive for the trailer owner to purchase fuel-saving devices.

The report also recommends that the agencies adopt a regulation requiring that all new 53-foot or longer dry van and refrigerated van trailers meet performance standards that will reduce fuel consumption and CO2 emissions. The lead time to implement this regulation should be evaluated independently from lead time requirements applicable to the next set of standards for new engines and tractors, because less time is needed to perform compliance testing and install aerodynamic devices on new trailers. The agencies should also collect real world data on fleet use of aerodynamic trailers to help inform the regulation, the report suggested.

NHTSA, in coordination with EPA, should also determine whether it would be practical and cost effective to include with the regulation of van trailers the regulation of other types of trailers such as pups, flatbeds and container carriers, as doing so could substantially increase overall fuel savings.

Other major recommendations from the report include:

  • NHTSA, in consultation with EPA, should consider carefully the impact on related metrics when attempting to optimize for a single metric, or should otherwise establish a clearly articulated objective that weights, or places limits upon, relevant metrics.

  • NHTSA should investigate allowing the OEM to substitute OEM-specific models or code for the fixed models in the current GEM, including substituting a power pack (the engine, aftertreatment, transmission). These models, whether provided by OEMs or fixed in the code, should be configured to reflect real-world operation accurately.

  • A mechanism needs to be implemented for obtaining accurate tire rolling-resistance factors, including equipment calibration, and maintaining that information in a public database. This might be managed in the same way that tread wear, temperature, and traction data are displayed through the federal Uniform Tire Quality Grading system.

  • The choice of test cycles/routes or schedules used in GEM needs to be readdressed thoroughly to avoid creating designs that are optimized for the test rather than achieving real-world performance in the design process.

  • NHTSA should establish a repeatable, reliable fleet data collection process as soon as possible. In addition to continuing data procurement with SwRI and R.L Polk, NHTSA should investigate outside sources (such as FTR, ACT Research, SmartWay, the North American Council for Freight Efficiency (NACFE), and the American Transportation Research Institute (ATRI) to obtain a repeatable, reliable baseline as well as future data. These sources could use the R.L. Polk data and conduct clarifying, deeper interviews with truck and trailer builders, manufacturers, and fleets for specific ongoing data on technologies procured, and fuel consumption.

  • To benefit fully from the GHG and petroleum displacement potential of natural gas, government and the private sector should support further technical improvements in engine efficiency and operating costs, reduction of storage costs, and emission controls (as is done for diesel engines). NHTSA and EPA should also evaluate the need for and benefits and costs of an in-use natural gas fuel specification for motor vehicle use.

  • NHTSA should evaluate the relative fidelities of the coastdown procedure and candidate powered procedures to define an optimum prescribed full-vehicle test procedure and process; and should validate the improved procedure against real world vehicle testing. Further, the Agencies should assess if adding yaw loads to the validation process provides significantly increased value to the Cd result. In addition, the Agencies should disseminate to end users updated test data and fuel savings of efficient trailers, aerodynamic devices, and tires, especially to those not participating in the SmartWay program. This should increase end-user confidence in fuel savings and device reliability.

  • NHTSA, in coordination with EPA, should further evaluate and quantify the rolling resistance of new tires, especially those sold as replacements. If additional, cost effective fuel savings can be achieved, NHTSA should adopt a regulation establishing a low rolling resistance performance standard for all new tires designed for tractor and trailer use.

  • NHTSA, supported by EPA, should expeditiously establish and validate the equipment and process of a tire industry machine alignment laboratory and mandate the use of that laboratory by each tire manufacturer seeking Crr validation for any tires being offered as candidates in the GEM computation process, just as the Crrs of light-duty vehicle tires were validated.

  • NHTSA should consider additional strategies to encourage the adoption of measures that reduce fuel consumption and attempt to quantify the impacts of non-technological factors on the costs and feasibility of future efforts to improve fuel consumption.

  • NHTSA, in coordination with EPA, should begin to consider the well-to-wheel life-cycle energy consumption and greenhouse emissions associated with different vehicle and energy technologies to ensure future rulemakings best accomplish their overall goals.

  • NHTSA should conduct an analysis, including methods such as expert surveys and scenario analysis or red teaming, as appropriate, to anticipate and analyze potential unintended consequences of its regulations and to determine whether additional actions are warranted to try to minimize such impacts. NHTSA should undertake this analysis concurrently with its next revision to its regulation.

  • NHTSA’s Phase II Rule should take the current and projected incremental fuel consumption reductions and penetration rates of the various technologies into careful consideration: These incremental reductions and penetration rates should be updated from those that were projected in the Phase I Rulemaking. Furthermore, system interactions should be evaluated for the effect on the projected incremental reductions whenever combinations of technologies are considered.

A number of strategies that do not involve changes to the engine or vehicle are also available for reducing fuel consumption, the report says. These include changes to fleet operations and logistics; innovations in infrastructure; traffic management,;and driver training and other behavioral initiatives. Market or regulatory factors may also directly or indirectly affect fuel consumption.

NHTSA should carefully consider and attempt to quantify the impacts of these nonvehicle approaches on the costs and feasibility of future fuel consumption improvements, and work with EPA, Federal Highway Administration, US Department of Energy, and the private sector to create incentives that capture the benefits of approaches other than regulating the vehicle.

The report was sponsored by the US Department of Transportation. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, independent nonprofit institutions that provide science, technology, and health policy advice under a congressional charter granted to NAS in 1863. The National Research Council is the principal operating arm of the National Academy of Sciences and the National Academy of Engineering.



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