A robotic car built by university students and backed by General Motors won the $2-million US top prize at a Pentagon-sponsored race designed to test robots for deployment in urban battlefields.

A souped-up Chevrolet sport utility vehicle — nicknamed "Boss" and built by engineering students from Pittsburgh-based Carnegie Mellon University — finished first on Saturday to win the Defence Advanced Research Projects Agency (DARPA) Urban Challenge.

It was one of 11 finalists competing in Saturday's race, which took place on a 96.5-kilometre course modelled after a real city and on the site of an old air force base in Victorville, Calif.

A team from Stanford University won the $1-million US second prize, while Virginia Tech's Victor Tango team won the third place prize of $500,000 US. Stanford had won the previous DARPA road race in 2005.

The robot vehicles had to complete the course within six hours, obey California traffic laws and operate without input from their human creators unless for safety reasons in order to qualify for the prize money.

DARPA held the race to help make good on a congressional mandate that "one-third of the operational ground combat vehicles are unmanned" by 2015. The race is designed to simulate military supply missions.

On race day, only six of the 11 finalists completed the three required missions before crossing the finish line. Only four were able to accomplish the tasks in under six hours.

It's the third DARPA-funded race for autonomously driven robotic vehicles, but the first to take place in an urban setting.

The previous two races, held in 2004 and 2005, took place on a desert course. Stanford had won the previous DARPA road race in 2005, while no vehicle finished the 2004 race.

Alan Mackworth, a University of British Columbia computer science professor and past president of the Association for the Advancement of Artificial Intelligence, said before the race the interest of car manufacturers like GM, Ford and Volkswagen has allowed major advances in the kinds of tasks the robotic vehicles are able to perform.

"This competition is forcing development of what will be the next generation of smart cars," said Mackworth.

Singapore and the United Kingdom have announced similar contests to test robots in urban environments, with the final round of both competitions scheduled to run in August 2008.