Car accidents fall into several major categories (whose names are self-explanatory):

* Rear-end collisions
* Rollovers
* Head-on collisions
* Single-car accidents
* Pile-ups
* Railroad crossing accidents

Collisions can occur with other automobiles, other vehicles such as bicycles or trucks, with pedestrians, and with stationary structures or objects, such as trees or road signs.
The result of a side collision; most cars are not as structurally sound side-to-side as they are front-to-back and damage can be more severe to the vehicle and the occupant than at the same speed in a rear-end collision.
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The result of a side collision; most cars are not as structurally sound side-to-side as they are front-to-back and damage can be more severe to the vehicle and the occupant than at the same speed in a rear-end collision.

In a collision between two cars, the occupants of a car with the lower mass will likely suffer the greater consequences.