Theory 194/Traffic jams/Threshold lens
Breakdown Needs a Density Threshold
The claim
Flow breaks down above a threshold in the ratio of density to capacity, so a small perturbation at high density produces a jam that the same perturbation would not at low density.
01Mechanism
Near capacity, the flow is unstable; the ratio determines whether a perturbation grows.
02Prediction
Breakdown should track the ratio.
03Refutation
Breakdown tracking demand alone would remove capacity.