In New York, generally, rear-end accidents are the fault of the motorist who hits the vehicle in front. It is easier to explain by providing an example: if the motorist is driving too fast or is texting while driving, he is less likely to stop in time to avoid hitting the vehicle in front.
Moreover, if the driver fails to brake in time, does not maintain control of the vehicle, fails to yield, or fails to maintain a safe distance between his car and the car in front of him, he is much more likely to be involved in a rear-end accident.
New York laws will hold the rear motorist liable for the accident, unless he can provide a valid explanation for why he was unable to avoid the accident.
Remember, this is not legal advice so contact a car accident attorney for more questions.