‘Jamitons’ slow the traffic flow
The motorway traffic is quite heavy but at least it is moving at a reasonable speed – until suddenly you see a jam ahead. Oh no, you think, an accident, a breakdown or roadworks. After a few stationary minutes everything moves forward again, and you see no cause for the hold-up.

Researchers at Massachusetts Institute of Technology used equations from fluid dynamics to understand how such “phantom jams” form in heavy but free-flowing traffic with no obvious cause. A small disturbance, such as a driver braking abruptly, is amplified into a stoppage they call a “jamiton” (by analogy with the self-sustaining solitary waves known in physics as solitons).