I assume the reason for the re-appear in the middle of the road is due to the common (for some people) problem where: after going a certain distance away from a vehicle it may sink into the ground and disappear. When this happens it will either disappear forever or reappear back on the nearest path (middle of the road in many cases) - the latter usually occurring when the game isn't able to 'forget' the vehicle (a spoosh'd vehicle would fall into this category, for example).