According to Honda Aims to Arm Its Cars With Unusual Safety Systems, Honda has designed a new “collision mitigation brake system” that detects impending collisions and alerts the driver:
The system uses computers linked to a radar sensor on the front bumper to detect if the vehicle is gaining too quickly on a car ahead. If an accident seems likely, a buzzer goes off. If that fails to get the driver’s attention, a small motor tugs three times on his seat belt to wake him. At the same time, the brakes are activated to slow the car. The computers won’t bring the car to a stop on their own, but if all goes well, by this time the driver is awake and hitting the brakes himself.