h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

A similar effect can be seen on a busy motorway - a phenomenon known as 'slinky-ing'...
For the sake of science, we shall say that you have three lanes of traffic, with the middle lane travelling slightly faster than the inside lane, and the outside lane travelling slightly faster than the middle lane. At some point, someone wants to change lanes, and because of the weight of traffic, the car that it moves in front of has to slow down. The driver behind this car sees the brake lights and slows down also. This carries on way, way back along the road. If everyone reacted instantaneously, this would not cause a major problem. However, what usually happens is that each consecutive driver brakes for slightly longer than the driver in front, with the result that, miles back along the road, cars have slowed right down to walking pace.
This message has nothing to do with being caught every day in the jams at the M62 / M60 interchange. Oh no...

Compression waves, I call them.

The trick is to take your foot of the gas, and not hit the brake. Also, you MUST leave enough room between the cars. Of course, this allows the idiots to cut into your lane, making you slow down to keep your distance.

It requires cooperation from everyone, and I don't think that will ever happen in a free society. It's one of the frustrations we must live with.

Dan