This is a toughie. It's actually better for traffic if people merge as close as possible to the lane closure. It's called a zipper merge, and the cars alternate (like teeth in a zipper) from the two lanes into one. The problem is, it only works when everyone does it. And everyone doesn't do it, so things get all messed up. If either lane has to come to a complete stop, it's a significant impact to traffic. You want people moving at a slow but constant rate of speed. New York's solution to this is to force you to merge MILES before the actual merge point, with long lines of traffic cones. New York drivers' solution is to mow down the traffic cones.