I was backing out of my driveway, which is on a busy street. I waited for the traffic to clear. I backed out onto the main road, which I thought was completely clear, but a car came behind me and I smacked right into him. There was no beeping from my car, and the automatic braking system did not engage at all. The rear of my car, particularly the driver's side, was severely damaged. The other car's passenger front door was badly damaged. The side curtain airbag on their car deployed and their vehicle (Volvo station wagon) was not driveable. The emergency braking system frequently engages unexpectedly when I back out of my driveway, even when there is no hazard. The unexpected braking is oftentimes dangerous. However, this time, when I needed it, it did not engage. An outside diagnostic inspection was done on the vehicle, and showed "no event." If you saw the cars involved in the accident, it is clear there was a significant "event."