What helps to reduce traffic bunching on a motorway?

Traffic bunching and variable speed limits

In an Exeter University study reported in the Independent:

They discovered that under certain conditions, when cars are bunched in a specific density and travelling at a specific speed, a single driver over-reacting can set off a braking shockwave that will build momentum and travel back along a motorway for miles.

Variable speed limits, which can be controlled manually or automatically, can help reduce this type of effect which can be quite significant. Below is a very short video in which scientists recreate traffic bunching on a circular road.