Federal Vehicle Standards
The transportation sector is now the largest source of U.S. carbon dioxide emissions, according to measurements from the Energy Information Administration, passing the energy sector in carbon dioxide emissions in late 2016. Cars and light-duty trucks are responsible for approximately 61 percent of transportation emissions. Medium- and heavy-duty vehicles, which include tractor-trailers, large pickups and vans, delivery trucks, buses, and garbage trucks, produce approximately 23 percent of transportation emissions.
The federal government has regulated the fuel economy of cars and light-duty trucks for decades, with the final rules in 2012 increasing fuel economy and decreasing greenhouse gas emissions. A 2010 rule raised the average fuel economy of new passenger vehicles to 34.1 miles per gallon (mpg) for model year 2016, a nearly 15 percent increase from 2011. A second rule, finalized in 2012, aims to raise average fuel economy to up to 54.5 mpg for model year 2025, for a combined increase of more than 90 percent over 2011 levels. The standards are also expected to reduce the carbon intensity of these vehicles by 40 percent through 2025.The standards were adopted by the Environmental Protection Agency (EPA) and the National Highway Traffic Safety Administration (NHTSA) with the cooperation of major automakers and the state of California. Together, the standards represent the largest step taken by the federal government directed at climate change.
Other benefits include improving U.S. energy security and cost savings for drivers. The car rule for model years 2017 to 2025 is projected to cut annual U.S. oil imports by an additional 6 percent, or 400,000 barrels per day, by 2025 over projections without the rule. When combined with the rule for model years 2012 to 2016, U.S. oil imports are expected to decline by more than 2 million barrels per day by 2025. The higher cost of vehicles with fuel efficiency improvements will be far outweighed by fuel savings, with the average driver saving thousands of dollars over the lifetime of a model year 2025 car compared to a model year 2010 car.
Fuel economy and greenhouse gas standards were first established for medium- and heavy-duty vehicles in 2011. In August 2016, EPA and NHTSA finalized new Phase Two fuel economy standards for model years 2021-2027.
Figure 1: Transportation sector CO2 emissions by source
Source: U.S. Environmental Protection Agency (EPA), Inventory of U.S. Greenhouse Gas Emissions and Sinks: 1990–2013 (Washington, DC: U.S. Environmental Protection Agency, 2015), http://www.epa.gov/climatechange/Downloads/ghgemissions/US-GHG-Inventory-2015-Main-Text.pdf.
Figure 2: Rolling 12-month CO2 emissions by sector
Lines show how the rolling 12-month CO2 emission totals from the transportation and power sector have changed from January 2014 to November 2016 (refer to the left-hand axis for the units). Transportation sector emissions surpassed power-sector emissions in March 2016. Columns represent each sector's percentage of total energy-related CO2 emissions for the 2014 and 2015 calendar years. The power sector's share plummeted from 2014-2016, while transportation’s share continued to climb (refer to the right-hand axis). Source, U.S. Energy Information Administration, 2016. https://www.eia.gov/totalenergy/data/monthly/#electricity
The federal government has regulated fuel economy through standards for cars and light-duty trucks for decades. The 1973 Arab oil embargo prompted Congress to pass legislation in 1975 that introduced Corporate Average Fuel Economy (CAFE) standards for new passenger vehicles only. The purpose was to improve the fuel economy of the passenger vehicle fleet to reduce oil imports.
NHTSA, an agency within the U.S. Department of Transportation (DOT), administered the original CAFE program while EPA was responsible for establishing the testing and evaluation protocol for assessing compliance and calculating the fuel economy for each manufacturer. These responsibilities are the same today.
CAFE is the sales-weighted average fuel economy (in mpg) of the passenger cars or light-duty trucks for a manufacturer's fleet. See Calculating Light-Duty Vehicle CAFE Then and Now below for details of how EPA determines compliance. NHTSA fines manufacturers that are out of compliance. NHTSA has so far collected more than $850 million in fines over the life of the CAFE program.
Since 1975, a number of changes have been made to the standards. Figure 3 provides an annotated history of the U.S. CAFE standards. A number of other countries have also instituted fuel economy standards, with most establishing more aggressive targets than the United States. See here for more details.
FIGURE 3: Fuel economy standard for passenger vehicles from MY1978-2025.
1. 1978-1985: Congress sets car standard (1978-1985)
6. Bush Admin issues new truck targets (2005-2007)
Under the federal Clean Air Act, California is the only state with the ability to set air emission standards for motor vehicles, as long as these standards are as stringent as the federal standards and the state receives a waiver from EPA. Once California receives an EPA waiver, other states can adopt California's standards.
In 2002, California enacted the Clean Cars Law (AB 1493) to set vehicle emissions standards for greenhouse gases. In April 2007, the Supreme Court ruled that EPA has the authority to regulate greenhouse gas emissions from the transportation sector under the Clean Air Act. In December 2007, a judge threw out a lawsuit by automakers attempting to block California from implementing AB 1493. The intersection of fuel economy standards and greenhouse gas emission standards was beginning to become clear (see here for more on California vehicle standards).
In June 2009, EPA granted a waiver allowing California to regulate greenhouse gas emissions from vehicles within the state beginning with model year 2009. On September 15, 2009, EPA and NHTSA issued a joint proposal to establish new vehicle standards for fuel economy and greenhouse gas emissions for model years 2012 to 2016, which were finalized on April 1, 2010. The joint proposal reflected an agreement among EPA, NHTSA, California, and most major automakers. California promptly agreed to adopt the federal standards in lieu of its own separate standard and maintained agreement with federal standards for model years 2017 to 2025 under the 2013 waiver granted for its Advanced Clean Car regulations.
Both the EPA and the California Air Resources Board reviewed the feasibility and appropriateness of vehicle standards for model years 2022-2025 in a midterm review. The EPA, NHTSA, and CARB released a draft Technical Assessment Report in July 2016 that informed a proposed determination by the EPA in November 2016 to maintain the current federal fuel economy standards. After opening a comment period that was required to conclude by 2018, the EPA issued a final determination on January 12, 2017 that maintained federal fuel economy standards through 2025. The final determination cited the success of automakers in meeting early fuel economy requirements and the seven-year growth in the U.S. automakers as reasons to expect that automakers could affordably continue to meet the standards. CARB’s own midterm review, which relied heavily on the Technical Assessment Report, found that automakers were successfully and affordably deploying advanced technologies to meet fuel economy requirements and the state’s Zero Emission Vehicle program.
The latest passenger vehicle standards, finalized in August 2012, cover passenger cars, light-duty trucks, and medium-duty passenger vehicles, from model year 2017 to 2025. The standards build off those set in April 2010 for model years 2012 to 2016. The standards are based on the vehicle's footprint, which is a measure of vehicle size (see Calculating Light-Duty Vehicle CAFE Then and Now).
Because NHTSA cannot set standards beyond model year 2021 due to statutory obligations and because of the rules' long time frame, a mid-term evaluation is included in the rule. Thus, standards for model years 2022 through 2025 are considered "augural" – or a prediction -- by NHTSA. The comprehensive evaluation by both EPA and NHTSA will allow for any compliance changes if necessary for the later years covered by the rule.
In March 2017, the Trump administration reversed the EPA’s January 2017 decision to finalize federal fuel economy standards set for 2022-2025. The EPA will review the financial and technological feasibility of the expected standards, and if any revisions are required, the agency will undertake a formal rule-making. Public comments on the original rule will be reopened through early 2018.As seen in Table 1, the greenhouse gas standard from EPA requires vehicles to meet a target of 163 grams of carbon dioxide equivalent (CO2e) per mile in model year 2025, equivalent to 54.5 mpg if the automotive industry meets the target through only fuel economy improvements.
TABLE 1: Projected Emissions Targets under the Greenhouse Gas Standards (g CO2e/mi)
Combined Cars & Light Trucks
Combined Cars & Light Trucks
As seen in Table 2, the fuel economy standard from NHTSA requires vehicles to meet an estimated combined average of up to 48.7 mpg in 2025. This estimate is lower than the mpg-equivalent of the EPA target for 2025 mentioned above (54.5 mpg) , because it assumes that manufacturers will take advantage of flexibility available under the law designed to reduce the cost of compliance. See Light-Duty Vehicle Program Flexibilities for more information.
TABLE 2: Projected Fuel Economy Standard (mpg).
Combined Cars & Trucks
Combined Cars & Trucks
This table is based on CAFE certification data from model year 2010, a car-truck sales split from the Energy Information Administration's Annual Energy Outlook for 2012, and future sales forecasts by JD Power.
Medium- and heavy-duty trucks make up only 5 percent of vehicles on the road but account for about a fifth of U.S transportation emissions. This category includes tractor-trailers, large pickups and vans, delivery trucks, buses, and garbage trucks.
The earlier standards, for model years 2014 to 2018, are cumulatively projected to save a combined $50 billion in fuel costs, 530 million barrels of oil, and 270 million metric tons of carbon emissions over the lifetime of the heavy-duty vehicles.
EPA estimates the new phase 2 standards for model years 2021-2027 will cut greenhouse gas emissions 25 percent from the final Phase 1 emissions standards, reducing greenhouse gas emissions by about 1.1 billion metric tons. EPA estimates the rules will also reduce oil consumption by nearly 2 billion barrels, and lower fuel expenditures by $170 billion over the life of vehicles sold under this standard.
In model year 2027, the buyer of a new vehicle would recoup the extra cost of technology used to achieve the standard within:
• 2 years for tractor/trailer combos
• 3 years for pick-ups and vans
• 4 years for vocational vehicles
EPA’s proposed Phase 2 standards would be phased in from model years 2021 to 2027, though proposed standards for some categories of box trailers begin in model year 2018. All proposed CO2 and petroleum use reductions are relative to the final Phase 1 standards, which are being implemented through 2017, with the exception of trailers, which had not previously been regulated. Notably, Phase 2 standards use different methodologies and test procedures, and should not be construed as directly comparable to Phase 1 standards. Trailer emissions can be reduced with the following technologies:
• Aerodynamic Technologies (different standards apply to Box and Non-Box Trailers)
• Tire Rolling Resistance
• Tire Pressure Systems
• Weight Reduction
Table 3 defines the breakdown for medium- and heavy-duty vehicles by weight.
TABLE 3: Vehicle class breakdown for medium- and heavy-duty vehicles
Gross Vehicle Weight Rating (lb)
8,501 – 10,000
10,001 – 14,000
14,001 – 16,000
16,001 – 19,500
19,501 – 26,000
26,001 – 33,000
The proposed standards described below represent Alternative 3 of the proposed standards, which would take effect in 2021 and would provide a full 10 years of lead time. Standards are divided into four segments.
- Combination Tractors, which are responsible for almost two-thirds of fuel consumption from medium- and heavy-duty trucks, would achieve a 24 percent reduction in fuel consumption by model year 2027.
- Trailers Pulled by Combination Tractors, which were not included under Phase 1 standards, would achieve a 9 percent reduction in fuel consumption by model year 2027.
- Heavy-Duty Pickup Trucks and Vans would have to improve fuel economy by 16 percent by model year 2027. The standards rely on a "work" factor, which considers the vehicle's cargo capacity, towing capabilities, and whether it has 4-wheel drive. Similar to the light-duty standards, the standards are based on the manufacturer's sales mix.
- Vocational Vehicles (delivery trucks, buses, garbage trucks) would achieve a 24 percent reduction in fuel consumption by model year 2027.
TABLE 4: Fuel Consumption Standards for Tractor-Trailers for Phase 1, Model Years 2014-2018
2014–2016 Model Year Gallons of Fuel per 1,000 Ton-Mile
2017 Model Year and Later Gallons of Fuel per 1,000 Ton-Mile
TABLE 5: Fuel Consumption Standards for Combination Tractors for Phase 2, Model Years 2021-2027
2021 Model Year Gallons of Fuel per 1,000 Ton-Mile
2024 Model Year Gallons of Fuel per 1,000 Ton-Mile
2027 Model Year Gallons of Fuel per 1,000 Ton-Mile
TABLE 6: Fuel Consumption Standards for Vocational Vehicles for Phase 1, Model Years 2014-2018
Light Heavy-Duty Class 2b-5
Medium Heavy-Duty Class 6-7
Heavy Heavy-Duty Class 8
Fuel Consumption Mandatory Standards (gallons per 1,000 ton-miles) Effective for Model Years 2017 and later
Fuel Consumption Standard
Effective for Model Years 2016
Fuel Consumption Standard
Fuel Consumption Voluntary Standards (gallons per 1,000 ton-miles) Effective for Model Years 2013 to 2015
Fuel Consumption Standard
TABLE 7: Fuel Consumption Standards for Vocational Vehicles, for Phase 2, Model Years 2021-2027
Light Heavy-Duty Class 2b-5 (CI/SI)
Medium Heavy-Duty Class 6-7 (CI/SI)
Heavy Heavy-Duty Class 8 (CI)
Fuel Consumption Standards (gallons per 1,000 ton-miles) for Model Year 2021
29.1 / 36
18.5 / 22.8
19.4 / 24.1
30 / 37
18.7 / 23.1
19.6 / 24.3
31.2 / 38.6
18.3 / 22.6
18.6 / 23
Fuel Consumption Standards (gallons per 1,000 ton-miles) for Model Year 2021
27.9 / 35.1
17.6 / 22.2
18.7 / 12.4
28.7 / 36.1
17.8 / 22.4
18.9 / 23.6
29.9 / 37.6
17.5 / 22.1
17.9 / 22.4
Fuel Consumption Standards (gallons per 1,000 ton-miles) for Model Year 2027
26.7 / 33.6
16.9 / 21.3
17.9 / 22.1
27.5 / 34.7
17.1 / 21.5
18 / 22.3
28.7 / 36.1
16.7 / 21
17.1 / 21.2
NHTSA and EPA designed the standards based on the kind of work the vehicles undertake. Heavy-duty pickup trucks and vans must meet a standard specified similarly to passenger vehicles, gallons of fuel per mile and grams of CO2e per mile. The other two categories must meet a standard based on the amount of weight being hauled (fuel consumed or grams of CO2e emitted per ton of freight hauled a defined distance). Vocational vehicles are separated by two classes of engine: Compression-Ignition (CI) and Small-Spark Ignition (SI).
U.S. fuel economy and greenhouse gas standards exist because individual drivers tend to value savings from fuel economy much less than society as a whole, which leads to more oil consumption than would occur if societal benefits were taken into account. The benefits to society of higher fuel economy include, but are not limited to, reduced impacts on global climate, improved energy security, and overall consumer savings. But those benefits are not top of mind when a consumer buys a car.
In addition, when making purchasing decisions, most people assume a dollar today is worth more than a dollar in the future since the dollar today can be invested and grow in value over time. The value people assign to a dollar in the future compared to a dollar today is known as the discount rate, or the interest rate they would expect on a dollar invested today. For example, a discount rate of 20 percent means consumers assume they will make 20 percent interest annually on money invested today, which is unlikely. Thus, the higher the discount rate a consumer uses, the more likely a consumer is to invest that money instead of spending it on a product.
David Greene from Oak Ridge National Laboratory found that the value consumers place on fuel economy savings for cars varies widely, but empirical research reveals a discount rate between 4 and 40 percent. The discount rate that society puts on fuel savings is much closer to 4 percent, meaning consumers often substantially undervalue fuel economy.
Each automaker's fleet-wide average fuel economy consists of three potential fleets: domestic passenger cars, imported passenger cars, and light-duty trucks. (The split between domestic and imported cars exists to support domestic automobile production.) With its focus on fuel efficiency, the standard must capture the fuel economy of each vehicle traveling the same number of miles. The harmonic mean of the fleet accomplishes this task (versus the simpler arithmetic mean). That is, instead of dividing the sum of the fuel economy rates in mpg for each vehicle by the total number of vehicles (the arithmetic mean), the reciprocal of the arithmetic mean is used as follows:
Where Production is the number of vehicles produced for sale for each model and TARGET is the fuel economy target for the vehicle.
Before 2008, the target fuel economy was the same for all vehicles. In 2008, NHTSA changed the target to a bottom-up one based on attributes of each vehicle instead of a top-down uniform target across an entire automaker's fleet. The vehicle footprint target for light-duty trucks through model year 2016 and for automobiles through model year 2025 is determined as follows:
where FOOTPRINT is the product of the vehicle's wheelbase and average track width in square feet, a and b are high and low fuel economy targets that increase from 2012 to 2025 and are constant for all vehicles, and c and d are adjustment factors. Parameter c is measured in gallons per mile per foot-squared, and parameter d is measured in gallons per mile.
For light-duty trucks beginning in model year 2017, an additional variation of the TARGET calculation is considered. This additional variation establishes a "floor" term, which prevents any footprint target from declining between model years. The definitions of parameters a, b, c, and d correspond to e, f, g, h, accordingly. However, the values of these parameters are different.
The idea behind an attribute-based standard is that the level of difficulty of meeting the standards is the same for smaller and larger vehicles. A uniform standard, on the other hand, is easier to meet for smaller vehicles (i.e., those with a smaller footprint) than for larger vehicles.
The EPA and NHTSA programs have a number of features to make compliance for manufacturers more cost-effective, while also encouraging technological innovation like plug-in electric vehicles. Since there are two programs to comply with, the details of both programs are stipulated below.
- Credit Trading System: Both programs include a credit system allowing manufacturers to carry efficiency and greenhouse gas credits forward by up to five years and backward up to three years to achieve compliance and avoid fines. Manufacturers can also transfer credits between cars and trucks of their fleet and trade credits with other manufacturers. Additionally, CO2 credits generated for EPA compliance from model year 2010 to 2016 can be carried forward as far as model year 2021.
- Air Conditioning Improvements: Both programs allow manufacturers to use air conditioning (A/C) system efficiency improvements toward compliance. For the NHTSA program, credits will depend on fuel consumption reductions. The EPA program allows credits for reductions in fuel use and refrigerant leakage, as well as the use of alternative refrigerants with lower global warming potential.
- Off-Cycle Credits: Current test procedures do not capture all fuel efficiency and greenhouse gas improvements available. Technologies that qualify for additional credit might include solar panels on hybrid vehicles, active aerodynamics, or adaptive cruise control. In addition, manufacturers can apply for credit for newer technologies not yet considered if they can provide sufficient data to EPA.
- Zero Emission, Plug-in Hybrid, and Compressed Natural Gas Vehicle Incentives: To encourage plug-in electric vehicles, fuel cell vehicles, and compressed natural gas (CNG) vehicles, EPA has included a credit multiplier in the rule for model years 2017 to 2021. In the compliance calculation for GHG Emissions, all-electric and fuel cell vehicles count as two vehicles beginning with model year 2017 and phasing down to 1.7 by model year 2021. Plug-in hybrid electric vehicles begin with a multiplier of 1.6 in model year 2017 and phase down to a value of 1.3 by model year 2021. Electric and fuel cell vehicles sold during this period will count as emitting 0 grams of CO2e per mile. There is no multiplier for model years 2021 to 2025 and EPA limits the zero-grams credit based on vehicle sales during this period. The cap for model years 2021 to 2025 is 600,000 for companies that sell 300,000 of these vehicles from model year 2019 to 2021 and at 200,000 otherwise. Beyond that number, manufacturers of electric and fuel cell vehicles will need to account for their upstream emissions (i.e., electricity generation or hydrogen production) using accounting methodologies defined in the rule.
EPA has also included credit multipliers for CNG equivalent to plug-in hybrid electric vehicles: 1.6 in model year 2017 and a phase down to 1.3 by model year 2021. Unlike electric and fuel cell vehicles, GHG emissions from CNG vehicles will be measured by EPA.
In contrast, NHTSA does not believe it has the legal authority to offer credit multipliers. Existing legal authority does allow NHTSA to incentivize alternative fuels, like natural gas, however, by dividing vehicle fuel economy by 0.15; in other words, an electric, fuel cell, or CNG vehicle that has a fuel economy of 15 mpg-equivalent will be treated as a 100 mpg-equivalent vehicle.
- Truck Hybridization: Both programs offer incentives to add battery-electric hybrid support to full-size trucks. Mild hybrid pickup trucks (15-65 percent of braking energy is recaptured) would be eligible for a per vehicle credit of 10 grams of CO2e per mile during model years 2017 to 2025 so long as the technology is incorporated into 20 percent or more of the company's model year 2017 full-size pickup production, ramping up to at least 80 percent by model year 2021. Strong hybrid pickup trucks (at least 65 percent of braking energy is recaptured) would be eligible for a credit of 20 grams of CO2e per mile per vehicle during model years 2017 to 2025 as long as the technology is used in at least 10 percent of the company's full-size pickup trucks.
- Transportation Sector Emissions Overview
- Comparison of Actual and Projected Fuel Economy for New Passenger Vehicles
- EPA Office of Transportation and Air Quality Regulations and Standards
- NHTSA CAFE Program
- Greene, D. (2010, February 9-10). Why the Market for New Passenger Cars Generally Undervalues Fuel Economy. Retrieved August 5, 2011, from International Transport Forum.