How effective are systems that warn a driver about an impending front collision, then slam on the brakes if the driver doesn’t act quickly enough?

A lot, says a paper recently published in IEEE Transactions on Intelligent Transportation Systems, IEEE Spectrum Tech Talk reports.

Researchers at Virginia Tech’s Center for Injury Biomechanics studied systems that rely on radar to tell the car when it is coming dangerously close to another vehicle’s rear bumper. Some of these systems deliver an audible warning when the distance between the car and the one ahead of it gets too narrow.

Others offer braking assistance if the driver responds to the warning by applying the brakes. Still another type attempts to bring the car to a halt with a huge braking force if the driver has not hit the brake pedal 0.45 seconds before the sensors predict that there will be contact.

Based on a U.S. Department of Transportation crash data, they concluded that in most cases, the electronic safety systems would slow cars down by about 35 percent — enough to cut the number of serious injuries in half. Better still, they say, 7.7 percent of rear-end collisions would be avoided altogether.

According to the U.S. National Highway Traffic Safety Administration, there were 5.4 million automobile crashes on U.S. roads in 2010, killing 33 000 people and injuring more than 2.2 million.