Is that burning man arrivals are spread out over a long period of about 5 days, but everybody wants to leave in a few peak periods. Festivals that have a more definite arrival time have to deal with it in both directions, and usually the venue is selected to deal with this. Burning Man picked its venue long ago when it was tiny, and it's in a very remote location with only one small 90 mile long road for most of the people coming.