The train stops too soon after it hits Hank's truck. A locomotive, to be able to pull the weight of itself and its cars, is moving fast enough so that in order to come to a full stop, it takes a good mile, at least, of track before the train will loose enough momentum to come to a halt. Remember driver's education training? How many car lengths for each 10 miles per hour you're going? The same principles of physics apply to the train, too.