Three engineers are sitting in the Toyota Prius, two in the backseat, one in the front passenger seat.

And behind the wheel?

Nobody.

Yet the car glides slowly forward, threading its way through a series of orange traffic cones, the steering wheel turning as if guided by some unseen hand.

This Toyota, customized by students at the University of Pennsylvania and Lehigh University, is much more than a car. It's a robot, and little by little the members of the Ben Franklin Racing Team are teaching "Little Ben" to drive by itself.

More than 80 similar projects are under way in labs and garages across the country, as engineers load their vehicles with gadgetry for the 2007 Urban Challenge: a rip-roaring, 60-mile spectacle sponsored by the research arm of the Pentagon. It is the third such event, ostensibly aimed at developing a new breed of driverless combat vehicle, but for participants it's the equivalent of the gearhead Olympics.

There is more than one way to keep your car from crashing into a tree, and all is fair game in this techiest of high-tech extravaganzas: Lasers. Video. Gyroscopes. Satellite-based navigation!

Entrants include the homegrown - Moorestown resident Mike Selzler, a software developer, is souping up a 1995 Ford Bronco - and the corporate, with some budgets in the millions.

The November competition is sponsored by the Defense Advanced Research Projects Agency, which is mindful of a congressional mandate that by 2015, one-third of U.S. ground combat vehicles be unmanned. Why risk soldiers on a supply mission when you can send a camera-equipped truck instead?

Some contest participants predict their innovations may also find their way into consumer vehicles. Indeed, some cars already have "smart" features; Lexus has a new model that can parallel-park itself, with some initial guidance from the driver.

Alain Kornhauser, faculty adviser for Princeton University's team, envisions cars with some sort of steering aid, which would be optional like cruise control.

"In not extremely difficult situations, you'd turn it on and let it steer for you," he said. "It doesn't really take a whole lot of intelligence to sit there and turn the steering wheel when you're going down the Jersey Turnpike."

But for now, all eyes are on the big race.

Unlike the first two events, in which cars proceeded one at a time on a fairly open desert course, this time the race takes place in a still-unidentified Western U.S. city.

And it won't just be trees and curbs they have to worry about.

This year, some of the obstacles will be moving.

Jerking back and forth

An icy wind is ripping across the parking lot at Boeing Rotorcraft Systems in Delaware County, where Little Ben has permission to practice driving.

Inside the car it is warm - too warm in one spot, as it turns out. First the engineers drive Little Ben the traditional way through the course. The second time, the car remembers the global-positioning coordinates, and slaloms through the traffic cones on its own.

But then it runs over one and comes to an abrupt halt.

Engineers open the rear hatch and huddle to diagnose the problem. Tully Foote holds up a piece of twisted black-and-red electrical insulation.

"We just melted a wire," says Foote, who is pursuing a master's in mechanical engineering at Penn. "Not big enough."

Then begins a quest for a bigger wire, taking various team members to two Radio Shacks, an auto-parts store, and the lab back at Penn.

Ninety minutes later, Ben is back on track.

Three times, it loops through a tight course. Three times, it nails it. And so far, the car's not even using the laser range-finder on top, nor the video cameras that will be fastened on later.

The cars need GPS to follow the map that race organizers will give them in November, assuming they get through qualifying rounds. Lasers or cameras will be used to see - and avoid - things that won't be on the map. Other cars, for instance.

"I'm worried it'll be too much like demolition derby," said Ben's team adviser, Dan Lee, an associate engineering professor at Penn.

His team members have broken the challenge into chunks. First, they had the car customized so the gas, brakes and steering all are controlled by electric motor - a system originally designed by a Louisiana company for disabled drivers who can't use their legs.

Then, Alex Stewart wrote software telling the steering motor how much to turn at any given moment, so Ben will travel in a smooth curve between Points A and B.

Stewart recently adjusted the computer code because the steering wheel was overreacting when the car got slightly off course, jerking back and forth.

"It was always over-correcting itself," said Penn's Jim Keller, one of the team members. "The system was way too sensitive."

Avoiding obstacles

Others are teaching Ben to make sense of the various shapes on his video screen, with software that perceives light, color and texture.

The car will have to distinguish between a lane line and a curb, for example. And it can't make the mistake of thinking an uphill slope in the road ahead is an obstacle to be avoided.

Cars must be fully autonomous. No remote control, except to hit the brakes in an emergency.

Ben has a couple of sponsors - Lockheed Martin Advanced Technology Laboratories of Cherry Hill and Maryland-based Thales Communications Inc. - but is looking for more. The team has spent $100,000 so far.

The payoff is big: Top prize is $2 million, then $1 million and $500,000 for runners-up.

Bragging rights are bigger.

No one finished the course in 2004. Five teams did so in 2005 (Stanford University won; Carnegie Mellon scored second and third.) Princeton lost control after 9 miles. Penn used a modified pickup truck but got a late start and didn't make the finals.

This time, Little Ben will be ready, predicted Lee, the team adviser. It had better be - soon.

A video presentation is due in April. Race organizers make site visits in the summer. Then come two qualifying events before the finals Nov. 3.

For these cars of tomorrow, the future is already here.

Look, Ma ... no hands. See a video of "Little Ben" moving on at http://go.philly.com/robotcar EndText

Contact staff writer Tom Avril

at 215-854-2430 or tavril@phillynews.com.