emission standards under its Clean Air Act authority. (These are discussed in more detail in Chapter 5 of this report, on natural gas.) The coordinated rules were both tailored to the same three regulatory categories of heavy-duty vehicles: (1) combination tractors; (2) heavy-duty pickup trucks and vans; and (3) vocational vehicles. The EPA GHG emission standards commenced with model year 2014,1 whereas NHTSA’s fuel efficiency standards will be voluntary in model years 2014 and 2015 and become mandatory in model year 2016, in order to comply with EISA’s 4-year lead-time requirement.

Following promulgation of the initial standards, NHTSA and EPA have commenced work on a second round (Phase II Rule) of fuel efficiency and GHG emission standards for MHDVs. The current NHTSA fuel consumption standards take effect in MY2016 and must remain stable for at least 3 years under the statute. New standards must provide 4 years’ lead time. Assuming the Phase II fuel consumption regulation is promulgated in calendar year 2015, the earliest the new fuel consumption standards could go into effect is MY2020, owing to the 4-year lead time requirement.2

President Obama issued The President’s Climate Action Plan in June 2013 (White House, 2013, p. 8), which states that the administration plans to work with stakeholders “to develop post-2018 fuel consumption standards for heavy-duty vehicles to further reduce fuel consumption through the application of advanced cost-effective technologies and continue efforts to improve the efficiency of moving goods across the United States.”

The EISA anticipates that the NRC will update its report at 5-year intervals through 2025. Pursuant to that statutory timeline, NHTSA entered into a cooperative agreement with the NRC to issue a final report by 2016. The NRC formed the Committee on Technologies and Approaches for Reducing the Fuel Consumption of MHDVs (see Appendix A for member biographies) in January 2013. Subsequently, the cooperative agreement was modified (see Appendix B for the statement of task) to include a report to be issued in early 2014 that would inform a possible Phase II rulemaking such as that contemplated in the President’s Climate Action Plan.


This section looks back at the NRC report Technologies and Approaches to Reducing the Fuel Consumption of Medium- and Heavy-Duty Vehicles (2010), specifically the impact it has had on NHTSA’s and EPA’s rulemakings.3 In the preamble to the proposal of the Phase I Rule, the Agencies provided a response explaining their rationale for accepting or rejecting the NRC’s recommendations.4 In what follows, the committee provides its own views on the relationship between the Phase I Rule and the key findings and recommendations of the NRC Phase One Report that are of continued relevance.

Metrics Used in the Regulation

The Phase One Report included the following recommendation:

Recommendation 2-1. Any regulation of medium- and heavy-duty-vehicle fuel consumption should use load-specific fuel consumption (LSFC) as the metric and be based on using an average (or typical) payload based on national data representative of the classes and duty cycle of the vehicle. Standards might require different values of LSFC due to the various functions of the vehicle classes, e.g., buses, utility, line haul, pickup, and delivery. Regulators need to use a common procedure to develop baseline LSFC data for various applications, to determine if separate standards are required for different vehicles that have a common function. Any data reporting or labeling should state an LSFC value at specified tons of payload. (NRC, 2010)

The Agencies (EPA and NHTSA) followed the NRC Phase One Committee recommendation to base the fuel consumption standard on the vehicle work accomplished, such as load-specific fuel consumption (LSFC). Class 7 and Class 8 trucks and vocational trucks have been addressed specifically in this manner, and Class 2b pickups are handled effectively as mentioned below. The Agencies also gave considerable thought and study to selecting representative drive cycles so as to ensure the regulation would reduce GHG emissions.

A further consideration is the gross vehicle weight assumed in the GHG Emissions Model (GEM) simulation, which for Class 8 vehicles is based on a payload weight of 38,000 lb, an intermediate load value. The Agencies adopted payload values for the GEM simulation calculations that are representative of real-world truck use, instead of merely


1 For purposes of this report, the term “model year” will be synonymous with “calendar year,” because unlike the light-duty vehicle sector, model years vary significantly among MHDV manufacturers, and so for the sake of simplicity and uniformity the calendar year is often used as the rough approximation for model year (MY).

2 If NHTSA adopted its standards in mid-2015 it could start applying those standards to vehicles certified after that equivalent date in 2019, creating a split model year. The statement of task therefore refers to the possibility of the Phase II standards beginning in 2019. For purposes of its analysis here, however, the committee will assume that the Phase II standards will begin to apply to the entire 2020 model year.

3 75 Fed. Reg. 74152 to 74456 (Federal Register/Vol. 75, No. 229/ Tuesday, November 30, 2010/Proposed Rules).

4 See also Factors and Considerations for Establishing a Fuel Efficiency Regulatory Program for Commercial Medium- and Heavy-Duty Vehicles (NHTSA, 2010).

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