Rear-end collisions pose the greatest danger on expressways due to the high speeds at which vehicles travel and the limited reaction time drivers have to sudden stops or slowdowns. On expressways, traffic flows rapidly, and if a vehicle stops or slows unexpectedly, the following vehicle may not have enough time to react, leading to a collision. This type of crash can often lead to serious injuries because of the impact speed, and it can also trigger a chain reaction, where multiple vehicles are involved in the collision.
Other collision types, like head-on collisions, are typically less common on expressways due to the design of the road (such as divided lanes) that separates opposing traffic. Collisions on the passenger or driver side occur when there is a lateral impact, often at intersections or when merging, but these situations are not as likely on expressways compared to rear-end impacts, making rear-end collisions particularly hazardous under high-speed conditions.