交叉路口经常发生碰撞事故，通常是因为此处有两条或多条道路相互交错。诸如左转、穿过路口、右转之类的驾驶行为都可能引发冲突，从而导致碰撞事故。具体而言，美国国家公路交通安全管理局（NHTSA）发现，左转是最主要的碰撞前会发生的危险事件，其发生概率为22.2%（基于所有碰撞事故总数）。此外，在交叉路口转弯或穿过路口时发生的碰撞事故中，大约有61%涉及到左转。

Crashes often occur at intersections because these are the locations where two or more roads cross each other. Activities such as turning left, crossing over, and turning right have the potential for conflicts resulting in crashes. Specifically, the US National Highway Traffic Safety Association (NHTSA) found that turning left is a leading critical pre-crash event and occurs in 22.2 percent of all crashes. Further, approximately 61 percent of crashes that take place while turning or rossing an intersection involve a left-hand turn.1