WASHINGTON — Legislation proposed by two U.S. senators could substantially raise the allowable weight limit for heavy trucks if passed.

The Security and Fuel Efficiency (SAFE) Energy Act — introduced last week by Sens. Byron Dorgan (D-N.D.) and Larry Craig (R-Idaho) — is an attempt to improve fuel economy by 4 percent in new vehicle fleets, including automobiles, medium trucks, and heavy trucks from 2012-2030.

The bill also authorizes the Dept. of Transportation to increase freight efficiency by raising the maximum allowable gross weight for highway vehicles from 80,000 to 97,000 pounds, “so long as road safety is not compromised.”

The politicians also want to expand the availability biofuels for cars and trucks. The bill calls for a total renewable fuels standard of 30 billion gallons by 2020, with the condition that the 2020 mandate must include 15 billion gallons that are not just conventional corn-starch based, but will include cellulosic and other feedstocks.

This would expand the supply and demand of biofuels creating the appropriate incentives and obligations for infrastructure, including the installation of blender pumps that can strengthen the demand side of the biofuels market while protecting business owners from potential financial hardship, the bill states.