A rear end collision is a traffic accident wherein a vehicle into the vehicle in front of it. According to the National Safety Council, over 2.5 million rear end collisions are reported every year, making them the most common type of automobile accident. Rear end accidents are also known as “whiplash accidents” because the nature of collision often results in a whiplash injury for the driver in the front car

Typical scenarios for rear-ends are a sudden deceleration by the first car, so that the following car does not have the time to brake and collides with the first. Conversely, the following car may accelerate more rapidly than the leading. Common causes of rear-end crashes in Massachusetts include: panic stopping, tailgating, rapid acceleration by the second car, and congested streets. A 2011 investigation by the Hingham Police Department found tailgating was the leading cause of injury crashes in the city, sending more people to the hospital than drunk driving or speeding.

In some cases, a defective vehicle claim may arise from a rear-end collision. In the past several years, a number of claims have arisen as a result of defective gas tanks or structural defects that exacerbate a crash. In other cases, large commercial trucks without override guards or other protective equipment can result in a higher chance of serious or fatal injury.

If the two vehicles have similar physical structure, crashing into another car is equivalent to crashing into a rigid surface. Crashing into another automobile of similar mass from behind is equivalent to colliding with a brick wall at half the speed. For instance, if you are going 50 mph and hit a parked car, it is like driving into a wall at 25 mph. The same goes for the motionless vehicle. This results in extraordinary destruction to the cars and its passengers.

In many cases, the risk of serious or fatal injury is exacerbated by the size of the respective vehicles. Being struck from behind by a larger vehicle can be devastating, and may even force you into the vehicle in front of you. Conversely, hitting the rear of a larger vehicle, particularly a large truck, can result in an “underride accident”, in which your car is forced beneath the leading vehicle.

Often rear end collisions are the result of inattentiveness on the part of the rear driver. Driver distractions such as the radio, passengers in the car, and especially cellular phones can lead to rear end collisions as they take the driver's attention away from the road in front of them. Commonly, rear end collisions are thought to be the fault of the rear driver. However, in circumstances when the forward driver creates a hazard that the rear car cannot avoid, fault lies with the forward driver.

A typical medical consequence of rear-ends, even in case of collisions at moderate speed, is whiplash. In more severe cases permanent injuries may occur. Other types of injuries common to rear end collisions are soft tissue injury of the lumbar spine, spinal cord injury, facial and head injury Passengers in the back of minivans do not benefit from the short rear crumple zone, and therefore are more likely to be injured or killed in a rear-end collision.

About 20 percent of people involved in rear end collisions exhibit symptoms of whiplash. Whiplash is not a medical term; it is used to describe "Cervical Acceleration-Deceleration" injuries, which is the rapid movement of the neck. The neck is a very delicate structure of tendon and bone. A whiplash injury may be the result of the stretching of the spine's anterior longitudinal ligament, which stretches or tears as the head snaps forward and then back. Neck, back, or shoulder injury as a result of a rear-end collision may include headaches, pain in the arms and legs and numbness.