WASHINGTON — Big question marks loom for automakers now that a 35-mpg fuel economy standard by 2020 appears certain to become law. And they'll need answers soon.
Federal regulators will swing into action almost immediately, sweating the details of the new law. They'll set different targets for vehicles with different attributes, most likely related to size.
The Senate last week approved an energy bill that raises fuel economy standards about 40 percent. President Bush is expected to sign the bill after a final vote in the House of Representatives this week.
The new law would kick in with the 2011 model year. That's when the industry must begin changing vehicles so they start to improve from today's average of about 25 mpg.
Regulators must start issuing rules under the new law by April 1, 2009. Each automaker has a different fleet mix, so each will have a unique standard to meet.
Automakers will watch most closely for how regulators differentiate among vehicles. One possibility is weight. Heavier vehicles would have easier targets. Another is footprint, the area bounded by a vehicle's four wheels.
The new law does not spell out intermediate fleetwide standards for the period from 2011 until 2020. But they must be toughened more than 3 percent a year, compounded, to reach 35 mpg by 2020.