President Bush Wednesday signed an energy bill that, among other things, sets the government on a course to start regulating fuel efficiency for heavy-duty trucks. It also requires that biofuels be blended with standard petroleum fuels on an annual schedule.

The bill raises fuel economy standards for automobiles for the first time in 32 years. Cars and light trucks will have to get combined mileage of 35 miles per gallon by 2020, a 40 percent increase from today's 25 mpg.
At one point, the House version of the bill contained a provision that would have required medium and heavy trucks to show a 4 percent annual improvement in fuel economy starting in 2016, based on the average of city and highway miles for each class of truck in 2013. After a vigorous lobbying effort by engine manufacturers and others, that provision was spiked in favor of a plan to figure out how to measure truck fuel economy, and then put economy standards in place.
Specifically, the law gives the National Academy of Sciences one year to study the issue, taking existing and potential technologies into account. When that study is done, the Energy and Transportation Departments and the Environmental Protection Agency will have two years to start writing a rule to set and enforce fuel efficiency standards for trucks.
The agencies will have to set test procedures as well as the appropriate metric for measuring fuel economy, taking into account the work the truck is doing and the operational conditions. At a minimum, the regulators will have to give truck and engine manufacturers four model years of lead time to meet the standards, and three model years of stability.
The law orders EPA to come up with standard specifications for biodiesel and establish an inspection program to enforce those standards. It also sets a schedule for annual increases in renewable fuels, including biomass-based diesel. And it calls for studies of the effect of biodiesel on engines and the adequacy of the biodiesel transport system.