Back in 1977 I took off five weeks and drove around the country. I was on an interstate in either Arizona or New Mexico tooling along at 75 mph and half the cars were flying past me (this was just a few years after the gas crisis and the national 55 mph speed limit was enacted). All of a sudden I saw a traffic jam ahead and slowed down to 55 (the speed that everyone else was doing). It was a three lane highway and there were ten to twelve rows of tightly packed cars traveling at exactly 55. I then noticed a state trooper car in the front of the pack (nobody dared pass him). It looked like the first lap of the Indy 500 with all the cars packed tightly together.

We drove for about ten miles and then the cop exited the parkway.. within five seconds everyone was doing 75 again.