I've seen police cars do this in really bad rush hours. They make a line so no one can pass and drive a consistent speed, thus clearing out the ripple effect of one person hitting the breaks, making a traffic jam.
That was a great video (oh, concrete jungle I don't miss you!). Next time I get in a traffic jam I'm going to think about being a "Zen Warrior" and being 10 whole seconds slower. Really - just better for all involved! I sometimes used to play a game to see how smooth and economical I could make my driving. It's actually a bit more difficult with a modern car that has less rolling resistance, to not brake sometimes.