Waves of denser, slower traffic generally are initially caused because some car somewhere has to slow down, maybe because they come up to a car that is moving too slowly or because many cars are trying to merge onto the road. The problem then continues because most drivers do not leave enough space between them and the car in front of them. If you leave too small of a gap in front of you, then you CAUSE traffic problems because it is more difficult for others to move into and out of the lane you are in, and because you must stop more suddenly when the car in front of you slows down.

The answer to traffic jams big or small is to allow a very large gap to accumulate in front of your car BEFORE you enter the traffic jam. This will probably have little effect on your rate of travel through the jam, but will help smooth all of the traffic behind you, which will help the jam clear faster. The worst things you can do are follow too closely and switch lines in such a way that drivers behind you have to slow down.

There are just so many variables – it must be a nightmare (assuming the engineer actually thought it through) trying to think of everything, anticipate all the consequences of all the design decisions knowing they have little option to change their design once implemented except to put up “Reduce speed!” signs.