The Bosch equipment also uses green lasers to bisect the car and create virtual lanes for the vehicle. Even the pitch of the windshield glass has to be perfect; otherwise, the sensors may look too far down the road and brake the car prematurely even when there’s no danger of a collision, Mr. Webley said.
Some models may specify that recalibration be done with a full tank of gas (to account for the precise height of the vehicle). Others require recalibration even after such seemingly minor adjustments as changing the wheel sizes on your car, Mr. Calkins said.
Still other vehicles, including cars from Ford, General Motors and Dodge, require what is known as dynamic recalibration, meaning the vehicle has to be test-driven according to very specific parameters.
“The repair facility may drive it 25 miles,” said Richard Beckwith, senior manager at Allstate’s Tech-Cor applied research and collision repair center. “It’s not for a joy ride but just to recalibrate the lane-departure warning system.”
Mr. Webley demonstrated the process on city roads and highways. Using a scanning computer plugged into an S.U.V.’s onboard diagnostic port, we had to drive on roads with clearly marked lanes, not an easy assignment around New York City. The vehicle also had to be driven at over 50 m.p.h. for at least 20 minutes — in clear weather — enough time for the sensing system to confirm that it was correctly calibrated.
Some cars, like certain model years from Honda and Mercedes-Benz, require both static and dynamic recalibration, adding an hour or two of testing to a typical repair. That, plus the added cost of the components, has raised the price of repairs after a simple fender bender, according to AAA.
Replacing a cracked or chipped windshield, for example, in a car with automatic emergency braking, adaptive cruise control and lane-departure warning systems could cost as much as $1,600. Furthermore, many cars are now bristling with embedded ultrasonic and radar sensors. So a relatively minor driving misjudgment that damages a side mirror and rear bumper could require fixing rear radar sensors used with blind-spot monitoring and rear cross-traffic alert systems. The price? As high as $2,050.