Slow but sure took the $2 million purse in the second Darpa Grand Challenge. Using what its developers called a "tortoise strategy," an autonomous Volkswagen Touareg named Stanley exploited artificial-intelligence techniques to cover 132 miles of Nevada desert in 6 hours and 53 minutes, for an average of just over 19 miles per hour. Second and third in the Oct. 8 race, sponsored by the Defense Advanced Research Projects Agency, went to a pair of Hummers from Carnegie Mellon University. Sandstorm trailed the leader by 11 minutes and H1ghlander by 21 minutes. Of the field of 23 autonomous ground vehicles that started the race before 2,000 spectators, only five crossed the finish line, and one of those exceeded Darpa's 10-hour time limit. Still, the results vastly improved on last year's Grand Challenge, when every entrant either stalled or crashed within seven miles. Last year's starting field all tried to outpace one another with horsepower. This year, the top three winners swore off horsepower in favor of reliability, ruggedization and smarts. "Our focus was reliability from the start, and in the end it was reliability that won the race," Bradski said. With two entries, Carnegie Mellon tried a tortoise-and-hare approach. H1ghlan-der, the "hare," had been favored to win, but ran into mechanical difficulties. "The pace we set for H1ghlander should have had it finishing 30 minutes ahead of [tortoise] Sandstorm. Unfortunately, H1ghlander had mechanical trouble that slowed down its pace," said professor William Whittaker, the CMU team leader. The brains of all three winning vehicles were identical, having been donated to Stanford and Carnegie Mellon by Intel, which permitted separate engineers to work with the rival teams. The computers used were six Pentium M processors, which were low power enough to run off the alternator in two of the three vehicles (H1ghlander had an auxiliary power generator supplied by Caterpillar Inc.). In-stead of laptops, the six Pentium M's were packaged as blades in a ruggedized platform designed to be earthquake proof (no spinning hard disks and a spike-resistant power supply). Each winning vehicle used one Intel 5091 chassis and six Intel MPCBL5525 processor blades. The Grand Challenge was conceived in 2002 by Darpa director Anthony Tether. The first race, in March 2004, offered a $1 million purse. When no one finished, the purse was upped to $2 million. So far, Darpa has reported spending about $20 million to organize and promote the Grand Challenge program. The agency has sponsored autonomous-vehicle research for more than a decade in hopes of meeting a Congressional mandate that one-third of all military vehicles be autonomous by 2015. Progress, however, has been so slow that Darpa decided to enlist outside help. Hence, the Grand Challenge.