A trick here is to stay in the HOV lane - there are no HOV restrictions in the afternoon going south. It will be a little strange, but stay in the left-most lane possible at all times (i.e., as soon as there's another lane on the left, get in it). That left-most lane will by-pass a lot of the traffic caused by the split. But make sure you end up going toward Virginia/Tyson's Corner, and not Silver Spring - which you achieve by staying to the left (the normal lanes toward VA veer off to the right.)