Rear-end collisions are usually considered the fault of the driver who rear-ended another vehicle. Sometimes these crashes are unavoidable, but often they are caused by a negligent driver.
It is possible that more than one driver may bear responsibility for causing a rear-end collision, especially when the crash involves multiple vehicles. In a rear-end collision pile-up, the last vehicles in the collision generally bear the most responsibility. However, careful analysis of the circumstances surrounding the accident will determine who is at fault.