When an automobile is hit from behind, the driver of the rear-ended vehicle can virtually always hold the other driver liable. This placement of liability is based on the basic rule of the road that requires drivers to be able to stop their vehicles safely if the car in front of them stops. Those who cannot stop without hitting the car in front of them are not driving in a responsible manner. When a third car hits the car in front of it and pushes it into the lead car, it is the driver of the third car who is at fault and against whose liability insurance the drivers of the front two cars would file their claims.
HINT: Tailgating is an inherently dangerous driving behavior that guarantees tailgater liability in the event that the driver is involved in a crash with the car ahead of it.