So, what if they do start bulldozing the thousands of cars tied up in endless traffic jams. The point is, it would ALL GET COVERED. The media simply could not ignore this. Now, they could spin what was "happening," but they absolutely could not deny that massive numbers of people were there in opposition to the government. And if DC is under "lock down?"
I think Abbie Hoffman would be proud of such an achievement.
As to how the Army gets there, that's easy - the 3rd Infantry is just over the bridges and there are other troops within the military district of Washington close to hand.
I know this sounds like a great idea - of course harking back to Abbie's levitating the Pentagon - but I think you underestimate the logistical difficulties. (Remember - amateurs talk tactics, professionals talk logistics)