If everyone just went to the end of the lane and zippered, traffic would flow so much nicer. Instead you get the people who dive in to traffic as soon as the dotted line appears... which means half a dozen cars go past them up the lane and at least another 1 or 2 of those people will also drop in to traffic prior before the end of the lane... which means instead of a nice 1:1 zipper at the end of a run that gives plenty of chance to match speed its more like 4:1 with 75% of them doing it with insufficient room which means people in traffic having to brake. And now you have the ripple effect causing a big slow down.