A new motion sensor for cars promises to keep drivers from backing into objects behind them.
Rostra Precision Controls in Laurinburg, North Carolina, has developed a system for detecting obstacles up to 12 feet away, whether they're in back or to the side of a vehicle.
"The system uses microwave motion sensing, and the microwave can go through plastic bumpers, and see through snow and mud," said Thomas Weiss, director of the automotive accessories group at Rostra. The devices sell for under US$300.
Conventional motion detectors use ultrasonic or infrared technologies, Weiss said, that can't see through bumpers. Therefore, they can't be hidden within the vehicle.
The 1999 Ford Windstar offers an ultrasonic backup motion sensor that can see through a plastic bumper. It's a $245 option, and is marketed as a parking aid.
The Windstar detector sounds warning beeps starting at 5.9 feet. The beeps get faster as the car gets closer to the obstacle, and change to a constant tone at 10 inches. The same device will also be an option on next year's Explorer and Mountaineer.
Weiss said conventional motion detectors don't necessarily detect obstacles in time to prevent accidents. "You have to wipe them off a lot. That's where [our] technology is easier for the consumer."
One material the Rostra can't see through is steel, so the sensor must be mounted below or in the front of steel bumpers.
The system detects an object based on its reflectivity. Obstacles that are perfectly flat or have many sharp points would be more difficult to pick up because they are less reflective.
Rostra has found a way to control the microwaves so the device won't pick up many false points, like grass. Its focused antenna design allowed engineers to narrow the microwaves, which would normally beam in many directions.
"It will pick up almost anything with reflectivity bigger than a basketball," Weiss said. "It will pick up everything from a dog to a child, to a one-inch pole, anything that a driver would normally see."
For liability reasons, however, Rostra is marketing the device as something designed to detect only cars. "We can't say it will pick up a dog, a cat, or a child."
The National Highway Traffic Safety Association (NHTSA) has studied pedestrian detection systems on school buses, and found them to be "promising" technologies, and that "the sensors ... work well and the systems do a good job of informing the driver as to when there is a moving object in front of or along the right side of the bus."
However, according to Riley Garrott of the Vehicles Research and Test Center at NHTSA, the agency is reluctant to endorse the sensors as safety devices because they can't detect a child who is stationary.
"They're probably helpful, but we're not absolutely sure of that because of the whole issue of the children who aren't moving," Garrott said.
"If you ride around on a school bus, most five, six, and seven year old kids are awfully antsy. Trying to get them to hold still is not easy to do. So how much of a problem is this really? We don't know, we never really answered that question."
According to NHTSA statistics, 72 percent of children killed in bus accidents are pedestrians.
The Rostra sensor uses an improvement on a Doppler radar-type technology to track obstacles.
"The technology has been out there since the 60s," Weiss said. "We just narrowed the target range and harnessed the microwave to be an active system on the back of a car."
