Gilly, are you sure that's the only sensor? If so, it's a poor design! Most cars have sensors located near the front of the car. SRS design engineers are always looking for ways how to sense an impending collision as soon as possible. The latest technology is looking for a way to incorporate forward radar sensors to the SRS systems. The idea is to set off the air bags even before there's contact between the two cars.
95 E320 Cabriolet, 131K