A rear-end collision, often called rear-ending or, in the UK, a shunt, occurs when a forward-moving vehicle crashes into the back of another vehicle in front of it. Similarly, rear-end rail collisions occur when a train runs into the end of a preceding train on the same track. Common factors contributing to rear-end collisions include driver inattention or distraction, tailgating, panic stops, brake checking and reduced traction due to wet weather or worn pavement.

Tailgating is the action of a driver driving behind another vehicle while not leaving sufficient distance to stop without causing a collision if the vehicle in front stops suddenly.