Carnegie Mellon University's Tartan Racing is among 53 teams to advance in DARPA's Urban Challenge.

Thirty-six other teams were cut from the robotic-vehicle competition. But Tartan Racing's Chevrolet Tahoe is in line to compete, without human assistance, in the Nov. 3 race through a mock urban area featuring traffic, curbs, signals and other obstacles.

DARPA -- the Defense Advanced Research Projects Agency of the Department of Defense -- next will assess whether each team's vehicle can perform tasks, operate safely and navigate through a four-way intersection with moving traffic.

"Every cut has to be taken seriously," said William "Red" Whittaker, CMU's Fredkin research professor of robotics and Tartan Racing team leader. "It's always great to be on the next step and that much closer to the competition."

The next cut Aug. 10 will leave 30 semifinalists to compete Oct. 21-31 in the National Qualification Event. The location of the Nov. 3 race hasn't been announced.

Each step requires more complex technology and the agency's upcoming site visits will be the first test with moving traffic. Dr. Whittaker said, "The challenges are profound.

"There is no part of this competition that is straightforward," he said. "The most difficult thing is, there is an infinite number of circumstances that could occur in machine driving in traffic, and it's not realistic in the short term to address all of those.

"The difficult things defy solution."

The Urban Challenge is the third DARPA-sponsored competition to foster development of robotic vehicles for eventual use on the battlefield. The challenge will simulate military supply missions in a mock urban area.

The Agency will award prizes of $2 million, $1 million and $500,000 to the top three finishers. In the 2005 competition, two CMU vehicles finished second and third behind Stanford University, whose vehicle was first to cross the finish line after 132 desert miles.

But creating a vehicle to drive through a city without human assistance requires a giant technological leap. Major teams have automakers as sponsors. General Motors is teaming with CMU.

Dr. Whittaker said his team has developed "great technical innovations" that help the robot see the world and figure out how to drive through it.

"Those technologies are elite beyond anything we know about, and they are important technologies for succeeding in the Urban Challenge," he said.