Seriously. When a car is pulled over to the side of the road, when a cop has his lights on, and is tending to an accident, when two or more cars have hit each other and are blocking traffic, the best thing you can do is:
1. Keep driving, maybe slowing down a bit to navigate around the situation.
2. Honk and wave.
3. Brake heavily, come to an almost-standstill, and crane your neck, hoping to see some gore, you idiot.
The answer is not #3. I become irrate when #3 occurs, because two seconds after the sideshow, traffic clears up and moves normally. What slows traffic down and backs it up for miles is people acting like total clambakes, looking at NOTHING. Please. Don't be a douche.