Two House Democrats have introduced a bill that would force the U.S. Postal Service to improve the fuel efficiency of its fleet of postal vehicles.

"The Postal Service is crippled by an inefficient, outdated fleet, and the vast majority of these vehicles are reaching the end of their operational lives," said Rep. Jared Huffman (D-Calif.), the lead sponsor of the bill. "Our nation's largest civilian fleet should serve as a global leader in efficiency and innovation."

Restocking the USPS fleet with fuel-efficient vehicles would seem to be a tall order at a time when the USPS is strapped for operating funds and is threatening to close offices and cut back on delivery service. But Huffman's Federal Leadership in Energy Efficient Transportation (FLEET) Act, H.R. 3963, tries to provide the funding by authorizing the USPS to enter into specialized contracts with the private sector in order to make the changeover more affordable.

Specifically, the bill authorizes the use of energy savings performance contracts, or ESPCs. These contracts already allow federal agencies to receive infrastructure improvements and pay for them over several years, sometimes a few decades, from the anticipated savings that the improvements generate.

For example, the U.S. Army already uses them to help pay for repairs and equipment upgrades with a minimal up-front cost.

Huffman says one study estimates that the USPS would save 150 million gallons of gas over the next decade, equaling $400 million, and says those savings would be used to pay for the upgrade.

Huffman and Rep. Gerry ConnollyGerald (Gerry) Edward ConnollyLights, camera, SCOTUS Bipartisan pair wants commission to oversee Iran deal Dem lawmaker warns of 'political and moral limitations’ to working with Trump MORE (D-Va.), who co-sponsored the bill, say USPS owns the world's largest civilian fleet of vehicles — 192,000 cars and trucks that drive 4.3 million miles each day. They say nearly 75 percent of those vehicles are old and average about 10 miles per gallon.

The bill would bring the USPS more into line with a 2009 executive order that requires vehicles at federal agencies to meet fuel economy standards. The USPS is an independent agency and was not covered by that order.