Consultant report

Benefits of state-level adoption of California medium- and heavy-duty vehicle regulations

This report evaluates the effects of adopting California heavy-duty vehicle emissions control programs in 13 states and the District of Columbia. These programs include the Advanced Clean Trucks (ACT) regulation, the Heavy-Duty Omnibus regulation, and full implementation of the California HD Vehicle Greenhouse Gas (GHG) Phase 2 regulation, including requirements on tractor-trailers.

Since California’s emissions control programs exceed the requirements of federal programs, the Clean Air Act allows other U.S. states to join the more stringent California programs provided the U.S. Environmental Protection Agency grants California a waiver from federal requirements and states delay implementation by two model years.

This analysis adopts the methodology developed by the California Resources Board to estimate the benefits of its own programs. The methodology is applied to other U.S. states taking vehicle population and activity projections generated from the U.S. EPA MOVES3 model at the county scale. Since California’s methodology limits its benefits accounting to electric vehicles (EVs) that do not migrate out of state and to the marginal increase in EVs from the ACT, the report includes a comparative analysis showing the benefits with these additional vehicles. These two approaches are described, respectively, as the ‘ACT Only EVs’ and the ‘All EVs’ approaches in the report.

Multiple combinations of regulatory program adoption were evaluated for the analysis, allowing states to understand the impact of each regulation on its own and in combination with the other regulations.

In-use electrical vehicle populations and new EV sales were projected for the calendar years evaluated. Changes in upstream emissions from increased demand for electricity are accounted for in this analysis. The annual change in well-to-tank emissions for both fossil-fueled and electric vehicles were projected using emissions factors from the Department of Energy for upstream power generation and petroleum refining emissions. Some states have policies to decarbonize their electricity consumption, and this analysis reflects the benefits of those policies using state-specific grid carbon intensity projections.

Estimates of annual avoided NOx reductions in 2050 ranged from 220 tons–350 tons per year in District of Columbia to 10,220 tons–17,110 tons per year in Pennsylvania. Well-to-wheel CO2-equivalent emission reductions range from 0.07 MMT–0.14 MMT in District of Colombia to 3.30 MMT–7.69 MMT in Oregon. There are several reasons for differences in emissions trends among these states. First, individual states have different vehicle age distributions, which influence the rate of fleet turnover, and different mixes of vehicle population by vehicle class. A few states provided state-specific estimates of vehicle miles traveled and vehicle population growth, which drive overall emissions levels. The largest determining factor for well-to-wheel CO2e emissions was the trend in carbon intensity of the electric grid. These emissions factors vary by region of the country, and seven areas (Colorado, the District of Columbia, Maine, Massachusetts, New Jersey, New York, and Oregon) provided state-specific projections for future penetration of renewable energy in their grids. These five areas had the largest net reductions for all pollutants.

A fact sheet summarizing the findings can be found here.

State-specific reduction estimates are available here.

This report was updated on November 16th to include updated data on Washington State. The previous version can be found here. The fact sheet summarizing the previous findings can be found here.