There is a phenomenon called "traffic shock wave." Let's say you have two cars side by side, each traveling at exactly the same speed (in this example 55 MPH). The two cars behind them cannot travel exactly the same speed, they must move at a speed slightly slower. So then, the next cars in line then must each slow even slower. Once you get to the 50th car, they are dramatically slower. 200th car....stopped.
Ever been in a long stand still on an interstate and after creeping for an hour, the traffic clears and there has been no accident to see? That is likely traffic shock wave. Somebody got into the left lane and drove exactly the same speed as the person in the right lane and bollixed up traffic for miles behind.
Hooray for the new law.
[ame]http://www.youtube.com/watch?v=Suugn-p5C1M[/ame]
JLK