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Cars Get Street Smart

No thanks to DARPA

5 min read

”Robot Cars Drive Themselves!” Pretty grabby headline, right? Throw in a few million dollars, a lot of publicity, and you've got a great story. The TV footage is compelling: brightly colored vehicles without drivers, bristling with cameras and sensors, driving themselves over dunes, down rutted trails--and, late this month, through simulated suburbs and city centers, in the US $2 million DARPA Urban Challenge.

There's just one problem with the imagery: the technologies likely to win the Challenge--those expensive cameras and sensors--probably won't be the ones that let future passenger vehicles ”drive themselves.” Instead, automakers expect that cars of the future will pay less attention to the lay of the land and more to each other, informing other vehicles about what they're doing several times each second by transmitting data that cars today already gather, via cheap wireless transponders roughly equivalent to your US $40 Wi-Fi router.

DARPA's interests are not in replacing commuters but in providing new and better technology for waging war. The appeal of an autonomous tank or rocket launcher is obvious: without soldiers inside, the potential casualties are reduced to zero. And the Department of Defense is under a 2015 deadline for making 30 percent of the U.S. military's land vehicles autonomous.

The challenge is substantial. An autonomous military vehicle must negotiate every kind of terrain: sandy desert, muddy forest, and dense urban core. To a tank, everything is a potentially hostile obstacle. Aside from its own location, tracked via the Global Positioning System, it has to figure out where everything in its surroundings is in real time.

Passenger cars, on the other hand, operate in far more limited circumstances: they stay on roads, almost all paved. They have no need to hide themselves, operate stealthily, or attack other objects. (In fact, making themselves known leads to avoidance, and hence safety.) And there are 250 million vehicles in the United States alone, according to the U.S. Bureau of Transportation Statistics, so traveling at high speeds among many adjacent moving objects with constantly changing trajectories is crucial.

Modern cars are stuffed with microprocessors and electronic control units that process data from a huge variety of sensors in the engine, transmission, suspension, and other systems--and then deliver the right blend of performance, fuel economy, and safety. Already, many traction-control systems simply ignore what drivers ask the car to do if the actions would cause the car to skid. Their sensors, though, are limited to the mechanical phenomena the car itself is experiencing.

Several safety systems have now added environmental data to the mix. Adaptive cruise control, from Mercedes-Benz and others, is one. It uses radar to calculate the distance to the car ahead and that car's velocity and adjusts its own speed to maintain a safe distance at all times--braking right down to a standstill and then accelerating back to highway speeds.

Another is the Volvo Blind-spot Information System (BLIS), which scans the area around a car's rear corners with side-mounted cameras and alerts the driver if there's a vehicle present. A third is Infiniti's Lane Departure Warning system: it calculates the edges of the lane from images captured by a video camera behind the windshield and alerts the driver if the vehicle is about to drift too far.

All of these systems still presume a vehicular environment that's mute. And that's one thing that will change over the next 10 years. Several initiatives around the world are considering standards for vehicle-to-vehicle (V2V) communications, in which new cars would be fitted with low-cost, short-range wireless transmitters. They would continuously alert surrounding vehicles (as well as elements of the highway infrastructure) to the vehicle's trajectory, the driver's actions, perhaps even the car's ultimate destination. The infrastructure, in turn, would alert cars to accidents, congestion, speed zones, vehicles nearing crossroads, and other conditions ahead.

But how many cars and signposts must communicate to make a difference? Larry Burns, head of R&D for General Motors, says the company's modeling shows safety benefits even with less than 10 percent of vehicles outfitted with transponders. That number might be reached just by retrofitting all rental cars and other large fleets, while new cars with factory-installed transponders gradually raise the overall ratio. Even if only every 10th car is communicating, a vehicle in the fast lane might ”hear” that someone just slammed on the brakes 15 cars ahead and start to slow well before the driver can see or react to the braking car ahead, says Burns.

A group of German automakers and component suppliers, along with Deutsche Telekom and several government ministries, is now writing requirements for a test in Hesse, in Germany's Rhine-Main region, that will equip more than 500 vehicles with transponders. Cars will communicate with each other but also with roadside units linked to central traffic control computers. The goal of the project, called SIM-TD, is to get real-world experience, including data that will help settle questions on what information is most useful. For example: Is a vehicle's relative trajectory adequate, or should it also transmit absolute position data from the navigation system? The first vehicles in this project are expected to hit the roads in 2009.

Photo: General Motors


A GM system warns of cars you can’t see.

Five large automakers in North America--Chrysler, Ford, GM, Honda, and Toyota--are now defining a V2V message set; they plan to equip 50 vehicles and 20 intersections with communications technology and start on-road testing late next year. Similar efforts are underway in Japan as well.

Roughly a year ago, GM offered journalists a glimpse of the potential of its V2V research in a demonstration held at Camp Pendleton, Calif. Each of us was asked to drive a Cadillac sedan at 40 miles per hour (64 km/h) toward another Cadillac stopped ahead in the same lane. As the distance narrowed, a colored indicator on the dash turned from green to amber to red. A warning tone sounded steadily louder and faster as the cars calculated that a collision was imminent.

Shortly after the indicator turned red, the moving car braked itself, staying in lane and coming to a halt just a few car lengths behind the stopped vehicle. Forward-looking radar can do the same thing, of course. But the cost of radar transponders and image-processing software and circuitry is far greater than that of a short-range wireless transponder incorporated into each car--transmitting data already gathered by existing in-car sensors.

The great promise is that one day, a vehicle might--if the driver chooses--even drive itself autonomously. Sure, everyone loves driving down country roads on sunny Sundays. But suppose your car could handle the heavy parts of that grinding, stop-and-go, 40-km suburban commute while you answered e-mail or concentrated on that conference call. The car would speed up, slow down, and choose its routes to minimize fuel usage and emissions. What's more, it would keep traffic flowing smoothly and enable more cars to occupy the limited road space, adding freeway capacity without the need to lay more concrete.

We're a long, long way from that point, of course. But one thing is clear: even if DARPA gets its robotic vehicles in time to meet the Defense Department's 2015 deadline, the car companies that serve everyday drivers won't be adapting military technology for civilian use.

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