Using Radar, Cameras and Algorithms to Fix Blind Spots
By ERIC A. TAUB
Published: October 24, 2007
AGE may make you wiser, but it also makes you stiffer. When it comes to driving, the effects of age become especially obvious when you're trying to swivel your head to check for blind spots, the areas to the side and rear of your car that remain outside your field of vision.
Blind spots are inherent in vehicle design, and manufacturers are studying ways to alleviate these conditions, particularly because baby boomers are growing old (and stiffer) en masse. The blind spots could be eliminated if manufacturers removed the side pillars that hold up the roof and made rearview mirrors that wrapped around a vehicle.
Given those impossibilities, some automakers have developed systems that use radar or video cameras to try to compensate for the realities of geometry and the limits of human sight.
Audi's Side Assist, available in its A8 sedan, Q7 sport-utility vehicle and other models next year, uses two radar devices in the rear bumper to monitor about 165 feet behind the vehicle.
When a driver puts on the directional signal to change lanes, a light-emitting diode in each side-view mirror illuminates to indicate there is a vehicle in that field of view. The light can be seen only by the driver, and it illuminates more quickly the faster the oncoming vehicle is approaching.
Algorithms used in the system enable it to warn about cars approaching from the rear and to ignore those that are falling back because they are slowing down.
General Motors' Side Blind Zone Alert system, available in certain Cadillac and Buick models, also uses radar to scan the rear and sides of the vehicle. The system sweeps outward 11 1/2 feet to the sides and 16 feet to the rear; a vehicle in the blind-spot zone will cause a light embedded in the mirror to illuminate. When the directional signal is used, the light flashes amber.
Volvo uses video cameras rather than radar for its Blind Spot Information System. Each camera, embedded in the side-view mirrors, monitors an area about 33 feet behind and about 10 feet to each side.
Vehicles approaching in the blind-spot zone cause a small light on the door near the side-mirror housing to illuminate. The company did not place the light in the instrument panel, having concluded that it would distract the driver, said Thomas Broberg, the department director for Volvo's Safety Center in Sweden.
The system is available for all of Volvo's cars. One limitation is that it monitors just the lane on either side of you; cut across multiple lanes in a sweep and you could still hit an unseen vehicle.
G.M.'s radar system is the first step toward a more comprehensive approach to avoiding collisions. By the end of this decade, the company expects to introduce elements of a vehicle-to-vehicle communication system. With this technology, G.P.S. and radio communications will allow one vehicle to alert another vehicle of its presence. Even if every vehicle will not have the system, the few that will can react to dangerous situations and reduce chances of an accident.
G.M. is discussing operating standards with its competitors. ''The cost of this type of system is one-tenth that of traditional radar coverage, and offers 360-degree monitoring,'' said Varsha Sadekar, the group manager for G.M.'s Active Safety and Driver Assistance Systems. ''Our long-term vision is total collision avoidance.''
But in reality, there is no definite evidence that the systems in production reduce accidents. ''It's quite hard to get data, as you're looking for a nonevent,'' Mr. Broberg of Volvo said.
It is also possible that using these systems may give drivers a false sense of security, causing them to let their guard down.
''I'm tremendously skeptical of these systems,'' said Chris Paukert, the editor of Winding Road, an online car magazine in Ann Arbor, Mich. ''I've used a number of these systems, and I turn them off. They cry wolf all the time.''
The National Highway Traffic Safety Administration recently began studying the systems and has not reached any conclusion as to their usefulness. Without such information, Mr. Paukert said he did not think the devices were worth the several hundred dollars they cost. ''I'd rather just focus my mirrors and know where I am,'' he said.
Mr. Broberg advised drivers to ''pay more attention when switching lanes and take more time.''
''Use your blinker,'' he added. ''In the U.S., a lot of people act like they don't want to waste it.''
Side mirrors should be adjusted to create a maximum field of view. To improve visibility, try to buy a vehicle that has large windows and small side pillars. Mr. Paukert particularly faults the Chrysler 300 for having ''gun-slit'' windows, and the Scion xB for having large rear pillars. ''You can hide half the Tour de France behind them,'' he said.
There is one inexpensive solution to reducing blind-spot dangers that the United States has yet to adopt: convex wide-angle driver's-side mirrors. (Now, flat mirrors are on the driver's side.) Identical to the ''Caution: objects in mirror are closer than they appear'' mirrors on the passenger-side front door, convex mirrors are common in the rest of the world but illegal here. The reason is that the government thinks that drivers might be confused by their distorted images.
''This is a very practical tool to help you deal with blind spots,'' said Filip Brabec, the general manager for product planning at Audi of America. ''I've greatly missed them in the U.S.''
People can buy aftermarket stick-on minimirrors that give that wide-angle look. European style convex mirrors are sold on Web sites, like vagparts.com. Although importing cars with them is illegal, it is not illegal for people to put them on after the fact, said Ron Medford, the senior associate for vehicle safety at the National Highway Traffic Safety Administration.
It is possible that the law preventing their use might change. ''We are concerned about convex mirrors' distorting the field of view,'' Mr. Medford said. ''But we are very much open to changing our rule.''
PHOTOS: HEADS UP: Audi's Side Assist system uses radar sensors in the rear bumper and warning lights in the side-view mirrors to alert drivers if there is a car in the blind spots. One display screen on the dashboard provides system information, while another allows the warning lights to be dimmed. (PHOTOGRAPHS COURTESY OF AUDI)