New report by the National Research Council calls for the federal Phase II Rule on fuel consumption and greenhouse-gas (GHG) emissions to include: A separate GHG/MPG standard for natural-gas vehicles A natural-gas fuel spec for motor vehicle use GHG/MPG “performance standards” for new, 53-ft and longer van/reefer trailers

NRC weighs in on Phase II of GHG/MPG rules

April 3, 2014
Report calls for separate GHG/MPG standard for natural-gas trucks; other actions

A report released this morning by the National Research Council (NRC) calls for the federal Phase II Rule on fuel consumption and greenhouse-gas (GHG) emissions to include:

  • A separate GHG/MPG standard for natural-gas vehicles
  • A natural-gas fuel spec for motor vehicle use
  • GHG/MPG “performance standards” for new, 53-ft and longer van and reefer trailers

The report also recommends considering the inclusion on a low-rolling-resistance standard for new tractor-trailer tires and urges that the rulemaking process be informed by fleet survey data.

The Phase II rule is to be issued jointly by the Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA) to address GHG/MPG requirements for medium- and heavy-duty commercial vehicles in the “post-2018 time frame,” noted NRC.

NRC is an operating arm of the National Academies, which is a private nonprofit chartered by Congress to provide expert advice.

The research organization stated that findings and recommendations from the congressionally mandated report that it completed in 2010 were incorporated into the Phase I GHG/MPG rule issued by EPA and NHTSA in 2011. In addition, NRC said it will issue a final report in 2016 that will “cover a broader range of technologies and issues and will address the 2025-2030 timeframe.”

Prepared by the NRC’s Board on Energy and Environmental Systems, Div. on Engineering & Physical Sciences, the report is titled “Reducing the Fuel Consumption and Greenhouse Gas Emissions of Medium- and Heavy-Duty Vehicles, Phase Two, First Report.” Following are highlights of the 160-pg report.

Diesel/Gasoline: Consider technology interactions

For starters, in looking at the 2019-2022 time frame NRC said the report “does not identify any new combustion or other engine technologies beyond those identified in the NRC’s 2010 Phase I Report that would provide significant further fuel consumption reduction during the time frame of the Phase II Rule.”

On the other hand, the research organization recommends that the Phase II Rule “should take the current and projected incremental fuel consumption reductions and penetration rates of existing technologies into careful consideration; these incremental reductions and penetration rates should be updated from what was projected in the Phase I rulemaking.

“Furthermore,” said NRC, “the report recommends that, whenever combinations of technologies are considered, interactions between those technologies should be evaluated for the effect on the projected incremental reductions.”

Natural gas: Separate GHG/MPG standard & vehicle-fuel spec

The report delves into what NRC described as the current “tradeoff” between diesel/gasoline-fueled and natural-gas fueled trucks: “Due to its low carbon content, the greenhouse gas emissions of natural gas are lower than for gasoline or diesel fuel, but this benefit is partially negated by lower efficiency in currently available engines and the higher GHG impact of methane— the main component of unburned natural gas. The GHG impact of methane leakage during gas extraction or other parts of the life cycle could negate the inherent tailpipe CO2 advantage of natural gas.”

Given those tradeoffs, the report recommends that NHSTA and EPA develop a separate standard for natural gas vehicles to “complement” the standards already issued for diesel- and gasoline-fueled vehicles.

NRC said that in establishing such a standard, the agencies should consider these factors:

  • Maximum feasible capability of natural gas engines to achieve reductions in GHG emissions and fuel consumption
  • Uncertainties involved with the various engine and storage configurations that use natural gas
  • Impact of duty cycles on the ability to comply with the vehicle standards
  • Cost of natural gas vehicle technology,
  • Rapid growth in market for natural-gas engines and vehicles

In addition, NRC said “more studies and data are also needed to determine the well-to-tank GHG emissions of natural gas vehicles, because extraction and leakage emissions of methane are not well quantified. NHTSA, in coordination with EPA, should assemble a best estimate of well-to-tank GHG emissions to be used as a context for long-term rulemakings beyond Phase II.”

The report also emphasized that there should be “urgency” to develop an “optimum solution” in the Phase II Rule for GHG/MPG requirements for natural-gas vehicles that will “accommodate” use of this alternative fuel without artificially disrupting prevailing commercial transportation business models.”

What’s more, said NRC, “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. NHTSA and EPA should also evaluate the need for, benefits of, and costs of an in-use natural gas fuel specification for motor vehicle use.”

Trailers: Create GHG/MPH standard for vans/reefers

Given that the majority of new and in-use van/reefer trailers are not equipped with aerodynamic devices (chiefly side skirts-- despite their proven and short payback— the report recommends implementing a regulation requiring all new, 53-ft and longer dry van and refrigerated van trailers to meet performance standards that will reduce their impact on fuel consumption and CO2 emissions.

NRC noted that NHTSA and EPA “should also collect actual operating data on fleet use of aerodynamic trailers to help inform the regulation”. The report also suggests steps to develop an “optimum full-vehicle test procedure.”

And the report advises that the two “determine whether it is practical and cost effective to regulate other types of trailers, such as pups, flatbeds, and container carriers, as doing so could substantially increase overall fuel savings.”

Tires: Consider a low-roll standard

The report recommends further evaluation and quantification of the rolling resistance of new tires-- especially those sold as replacements.

More to the point, it also suggests -- if “additional, cost-effective fuel savings can be achieved”— that a low-rolling-resistance standard be devised for all new tires designed for tractor and trailer use.

In addition, NRC said the report “urges NHTSA to expeditiously establish and validate the equipment and process of a tire industry Machine Alignment laboratory. NHTSA should mandate the use of that laboratory by each tire manufacturer seeking validation of tire rolling resistance coefficients for any tires being offered as candidates in the Greenhouse Gas Emission Model (GEM) computation process, just as light duty vehicle tires were validated.”

Vehicle Certification: Consider modeling & simulation

Turning to the nitty-gritty of vehicle certification, NRC said that the GEM (developed for the Phase I Rule used for the certification of Class 4-8 vehicles is ‘a simplified method for determining the effects of the vehicle (rather than the engine) on fuel consumption and GHG emissions.”

Given that assessment, NRC said it “could be improved to consider synergy between components, the operation or control of components in a most efficient way, and the operation of a smaller component at higher relative load to increase efficiency.”

In addition, NRC said that in using generic performance maps for major components, including the engine and transmission, GEM “does not credit the vehicle manufacturer with the benefits of using a potentially superior engine or transmission.”

The report also urges investigating whether to allow original equipment manufacturers the option to substitute OEM-specific models or code for the fixed models in the current GEM, including substituting a powerpack (engine, aftertreatment, and transmission). These models, whether provided by OEMs or fixed in the code, should be configured to accurately reflect actual operation.”

NRC said the report also recommends “reassessing the choice of test cycles/routes or schedules used in GEM to avoid creating designs that are optimized for the test rather than addressing actual performance in the design process.”

Regulatory process: Inform with fleet data

Delving into ways to improve the GHG/MPG rulemaking process, the report recommends that 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 also conduct an analysis to anticipate and analyze potential unintended consequences of its regulations.”

NRC also emphasized the need “to collect vehicle data that would permit regulators to evaluate the efficacy of and improve the accuracy of current and future regulations.”

Noting that NHTSA has begun designing surveys and seeking the necessary approvals to allow it to “assemble a picture” of the characteristics of commercial-vehicle fleets, the report also recommends that NHTSA “establish a repeatable, reliable survey process to collect private fleet data as soon as possible.”

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