It's a road race with no drivers, just cars. It's a Mad Max dash across the California desert, but no Max.

The Pentagon's Defense Advanced Research Projects Agency, the technological godfather of things stealth, smart bullets and the Internet, is sponsoring a road race this week --- with one overriding entry requirement.

Only robots need apply.

The race, called the DARPA Grand Challenge, begins Saturday at dawn at the Slash X Ranch near Barstow, Calif. The still-secret course is guaranteed to be a grueling grind over 200 miles of blue highways, back roads, trails and open desert from Barstow to the Nevada state line.

Twenty-five robots with assorted pedigrees --- modified Humvees, souped-up sport utility vehicles, dune buggies, all-terrain vehicles, a six-wheeled military truck and a motorcycle --- will vie for a congressionally authorized prize of $1 million.

The winner also gets bragging rights to one of the most daunting challenges robots have ever faced: that distinctly human, infinitely complex activity we call driving.

With or without a winner, the Defense Department's top research agency believes the interest generated by the race will stimulate some grassroots innovations that might be useful in future military robots. Under a congressional mandate to make a third of the country's military vehicles autonomous by 2015, DARPA has already funded dozens of research projects to develop machines that can replace human soldiers.

New ideas wanted

But they're still looking for a few good machines --- and the race is intended to draw out fresh approaches to robotics from universities and entrepreneurial companies that might never think about applying for million-dollar defense contracts.

Robotic contests aren't really new. There are hundreds every year --- robo-soccer championships, robotic egg hunts, robotic firefighting competitions, cleaning robot contests, even robotic sumo matches.Robots do a lot of serious work these days, too. They assemble automobiles, solder circuit boards, sweep floors, answer telephones, and even assist doctors in surgery. At the moment, roving robots are trundling across hostile terrain 100 million miles from Earth --- revealing details of a Martian landscape that no human has ever set foot on.

So far, however, robots haven't done much driving, and for good reason: They're not very good at it.

A robotic van "drove" from Pittsburgh to San Diego in 1995, but there was a human in the driver's seat, just in case. The van-bot did fine on interstate highways, but it never mastered the exit ramps and intersections. Robotics enthusiasts counter that 43,000 traffic fatalities a year prove humans aren't great drivers, either.

But Saturday's race is a sign of the changing times. These drivers are also the driven. For 200 miles, the entrants will be guided entirely by satellite navigation systems, racing through thousands of interim waypoints --- precise points of longitude and latitude --- to the finish line.

Computers and sensors aboard the vehicles will be entirely responsible for the steering, turning, braking and accelerating as they cross the desert.

The final course --- chosen from more than 1,200 miles of possible routes --- won't be disclosed to participants until two hours before the race.

The vehicles, including the University of Alaska's Arctic Tortoise, Louisiana State University's CajunBot and Virginia Tech's club car Cliff, will have 10 hours to cover the course.

Defense officials are promising that: "The route will include surfaced and unsurfaced roads, trails, and off-road areas. Manmade and natural obstacles --- both above and below the surface of the average terrain --- are likely. Examples of obstacles include ditches, washboard, open water, rocks, underpasses, construction, power line towers, barbed wire fences and other vehicles."
Opinions among robotics experts vary about whether the race should be known as the grand challenge or the impossible dream.

"You're talking about a course over very rough roads and open desert," says Frank Dellaert, co-director of Georgia Tech's robotics lab, which is not participating in the race. "I would have trouble driving some of these roads myself. I think it's beyond the capabilities of autonomous vehicles today."

One robotics team has already reinforced those sentiments. Team Overbot, made up of former Stanford University engineering students and Silicon Valley volunteers, dropped out of the race last month, announcing that they were "not able to deliver a safe autonomous vehicle in time."

Interest running high

Mark Maimone of NASA's Jet Propulsion Laboratory will watch the competition with special interest. He's well aware of the potential pitfalls. He wrote the software now being used by NASA's Mars rovers.

"It is a huge challenge to operate the rovers on Mars, but this is a lot different," Maimone says. "It takes the Mars rovers a minute and a half to scan what's ahead and make a decision. At the speeds these vehicles will be traveling, they are going to have to do that 20 times a second.

"The real challenge is to pull all of the sensing and control systems together and make them respond quickly," he says. "Robots don't do well with changing situations. The real world is very confusing to them."

A more confident Chuck Thorpe, director of the Robotics Institute at Carnegie Mellon University, says, "It's all going to depend on the course. Cliffs and ravines aren't the problem, but if there are nasty, tricky obstacles like water-filled holes you can't see the bottom of, or fence poles hidden behind a yucca plant, it may be no one will make it."

If any entrant does, Thorpe and other experts agree that it will very likely be Team Red, headed by his CMU colleague William "Red" Whittaker, who heads the school's field robotics laboratory and has 30 years of experience designing robotic vehicles.

Whittaker and more than 50 students have spent the last year building and testing Sandstorm, a 1986 Humvee that --- with $3.5 million in refinements --- reportedly does a pretty good job of driving itself.

Unlike other teams, Whittaker's has spent months building detailed maps of the possible race routes across the Mojave Desert. No matter how well a robot drives, it won't get where it's going if it doesn't know where it is --- just like a human driver.

The "computer farm" that serves as Sandstorm's road map holds 16 terabytes of data, enough to fill 100 hard drives on a desktop computer.

Another team, the Palos Verdes Road Warriors, may not bring as much robotic experience to the competition, but its members make up for it with youthful optimism.

The 40 gifted high school students, who each get five hours of research credit, are modifying a 2003 Acura SUV to enable it to drive itself, something many of them are still too young to do.

Under the tutelage of science teacher Graham Robertson, the Palos Verdes students have received donations of a new Acura SUV --- renamed Doom Buggy --- and $40,000 worth of electronic gear. From time to time, they also get a little friendly advice from engineers at nearby institutions like Cal Tech, the University of South California, NASA and the Jet Propulsion Laboratory.

Even DARPA has doubts about whether driverless vehicles will be able to conquer the California outback. If no one wins, the race will be run again next year. And the year after that.

"It's hard to say who came up with the precise idea for this Grand Challenge," recalls DARPA Director Anthony Tether. "We were having a bull session. In the military that's a bunch of generals sitting around a table.

"We were all thinking about, God, you know, these unmanned vehicles really are the way to go. But how are we going to energize people, how are we going to get people out of the garages?"

Racers, venue changed

Once the race was announced, energizing people was definitely not a problem: More than 100 robotics teams applied. Realizing that 100 robots racing across Southern California might be hard to manage, the agency cut the field to 25.

Also changed was the venue, originally billed from Los Angeles to Las Vegas. The idea of a pack of driverless vehicles roaring down Los Angeles freeways was deemed too ambitious for the current state of robotics technology.

Even with the empty quarter of the Mojave Desert between Barstow and the current finish line at Primm, Nev., DARPA is being careful. Judges will shadow each robot to make sure they don't run amok, or try to run each other off the road. Race rules require the robots to give the right-of-way to other vehicles.

Accidents, of course, are not always avoidable.

"They have insurance, just in case," says race spokesman Don Shipley, "They have taken out a lot of insurance."

And some fear that, at speeds that might reach 50 mph, the robots also pose a threat to the desert tortoise --- a federally threatened species and the official state reptile of California. Sluggish after a winter of hibernation, the tortoises usually emerge from their burrows this time of year.

Under orders from the U.S. Bureau of Land Management, teams of biologists will sweep the race corridor before the competition, moving any tortoises out of harm's way and fencing their burrows until the robots pass.

The tortoises, which have resided in the Mojave for 60 million years and, as individuals, often live to be 100, probably won't pay much mind.

Off-roading is common in this part of the desert. And from inside a tortoise shell at ground level, it's pretty hard to tell whether someone's behind the wheel or not.

HOW THEY NAVIGATE
Each vehicle travels the course through a series of waypoints. Each waypoint has a different circumference in which vehicles must enter before advancing to the next waypoint. If a vehicle goes outside the boundaries, DARPA can remotely shut off the vehicle.
Map shows course from START: Barstow to FINISH: Primm, Nev.
Shading indicates land elevations from sea level and below to 12,000+ ft.
Diagram of waypoints shows course line and areas where teams must enter.
Each waypoint determines vehicle speed. If a vehicle travels faster than the recommended speed, it will be disqualified.