I go to a (european) new year festival held in a valley with one exit. It's really bad for motorists, because the three or four roads around inside the valley converge on one narrow, steep exit road. To get in with their crutch, motorists have already chosen not to take the bus either from the head of the valley or from town, so we're not dealing with very smart people. The solution that this festival uses is to rank cars up in a carpark and release them in order, and encourage them to stop their engines while they wait. That concentrates the queue and reduces idling time as well as making it more social.

But the real solution is to cut down the number of motor vehicles. Last year bikes were free (had to buy a ticket but no car permit, $20 or so), buses were $5 each way per person (so three people in car saved money if you don't count fuel costs), next year it's going to cost more for the cars, and the buses will be cheaper I think.

It might not work on the playa, but for us we're trying to get a walking track put in, because right now you're not allowed to walk down the access road. It was hard enough to get bikes allowed, but we're working on pedestrians. It's only ~3km up or down, but it's about 3 hours drive at peak times.

The Vietnamese and Chinese new year festivals I go to just use the interminable queue system that burning man does. Which sucks, but those are not events that I can influence.