Theory 193/Traffic jams/Rate lens
Jams Move Backward at a Rate
The claim
A traffic jam propagates upstream at a rate set by the density difference across the shock, not by the speed of the cars in it.
01Mechanism
The boundary between free flow and congestion moves at the speed required to conserve vehicles.
02Prediction
Propagation speed should track the density difference.
03Refutation
Propagation tracking vehicle speed would remove conservation.