One of Darpa's slickest PR moves in years was to sponsor a robotic road race from Los Angeles to Las Vegas -- with a million bucks in cash going to the winner.

But now, there's trouble brewing for Darpa's "Grand Challenge", four months before it's slated to begin. Over 100 teams have signed up to take part in the race. But, in a surprise announcement, Darpa is saying that all but 20 of them won't be allowed to ride.

"There are factors beyond DARPA's control that limit the number of vehicles that can participate in the Los Angeles to Las Vegas event," the race's program manager, Col. Jose A. Negron, writes in a letter to racers. "The need to comply with environmental regulations, ensure the safety of the participants and spectators, and complete the event within the number of available daylight hours limit what can be accomplished in one day. Given these constraints, our analysis leads us to believe that only 20 vehicles can be allowed to run the Grand Challenge route."

How will the 20 teams be picked? By who spent the most? By who's got the fastest robot car? The letter doesn't say.

(via Robots.net)