:57 seconds in on this video, one truck hits a wall and becomes 2 trucks. How?

This video is from a surveillance camera in a tunnel in Europe (one which it might be a good idea to stay out of). At :57 seconds in, a very famous clip appears. A truck hits the wall and suddenly becomes two trucks. It could be a visual trick (there was a second truck in front of the first, but hidden to the camera) but one thing it is not is a CGI effect. Not only that, in the earlier frames, there is not the slightest sign of a second truck. So where did it come from?