U.S. computer scientists say new software for GPS devices can reduce energy consumption in transportation systems.

The program, GreenGPS, developed by computer scientists at the University of Illinois at Urbana-Champaign, works like normal GPS navigational devices except that in addition to calculating the shortest and fastest routes, it also suggests the most fuel-efficient route, a university release said Tuesday.

The software runs on cellphones linked to a car's computer using an inexpensive wireless adapter that works in all cars manufactured since 1996.

Information about engine performance and fuel efficiency is uploaded by the car's onboard diagnostic system to the phone, which uses the data to compute the greenest route.

"Currently at least 30 percent of total energy in the United States is spent on cars," UI computer science Professor Tarek Abdelzaher said. "By saving even 5 percent of that cost, we can save the same amount of total energy spent on the nation's entire information technology infrastructure."

A pilot program has seen units installed on 200 vehicles used by the Urbana-Champaign campus.

"The less money we can spend on fuel, the more money we can direct toward maintaining other things on campus," said Pete Varney, director of transportation and automotive Services.

In preliminary experiments, researchers found that following the suggestion of Green GPS saved 13 percent more fuel over the fastest route and 6 percent over the shortest.