I've gotten stuck in a traffic backup before, usually on long trips. I have to drive through PA to get to my parents house in WV and PA hasn't yet learned how to build roads and typically has to shut down large areas of highway to make emergancy repairs. I've learned that most vehicles are not equipped to handle ideling for many hours with the AC blasting. I've tried the front wheel drive minivan thing and a 2wd truck and both would have issues with the heat. The truck having a mechanical fan you could rev the enigne to get more air flow and get the temp back down but that used more gas. The minivan, being front wheel drive had electric fans so I eneded up having to turn off the A/C to keep from overheating.
My current truck I got the factory towing package so I could get the big transmission cooler sitting in front of the radiator to get the heat out of the transmission and not add it to the eninge. Most vehicles with automatic transmissions have a transmission cooler integrated with the radiator which causes the heat created by stop and go driving to heat up the engine coolant. So be sure to have either a manual transmission or install an external transmission cooler to prevent overheating. Now I can at least sit in the hot traffic with the A/C on as long as I have gas. So I'm careful to always make sure I have the tank good and full on those long trips.
I've seen quite a few people try to make U turns when traffic got backed up but the center divider on the highways is usually soft and wet, designed to trap an out of control vehicle to prevent it from getting on the other side going the wrong way. I've seen many people get stuck in this while trying to make a U turn and many a non happy Highway patrolman come to their 'rescue'. Be sure you have a 4x4 that can make it across before trying because that grass in the center hides the trap under it.