There's a common misperception that if you're the lead vehicle in a rear-end collision case that the rear driver is responsible 100% of the time; however, that is not true. The rear driver is not responsible all the time. There are some circumstances under which the lead driver may be held completely at fault or partially responsible for causing the accident. To answer the question, if you stopped suddenly and unexpectedly, really for no good reason, like you stopped at a green light, then you may be held partially responsible for the accident. Or, if you're parked illegally on the side of the road or in the middle of the road, and you're rear-ended, then you may be deemed at fault or partially at fault in that accident. There you can see some of the reasons why the rear driver is not always responsible for rear-end collisions.