Phantom Jam Lab
Ring 900 m

Phantom Jam Lab

One driver taps the brakes, and a kilometer back traffic stops dead. Mix tailgaters with drivers who leave ample distance and watch which jams form and which ones die out.

One driver leaves room

0:00
Click a car to inspect it · Space pause · B brake

Time-space record

Every line is one car's trip around the ring. Red bands sliding down the chart are jam waves moving backward against traffic.
Your mix
090 km/h Ample-distance driver Brake lights

Regime map

Two ratios decide whether a road of tailgaters flows or jams. Load Λ compares the cars on the road with how many fit at the speed limit and following time. Delay R is reaction time over following time. Click the map to move this road there.

Smooth Metastable Stop-and-go grows Small slowdowns start to grow (theory, live) A tap to half speed starts a jam (measured)

Live readout

Last 3 min
Your mix

Late reactions grow

A tailgater sees brake lights about a second late, so they brake harder than the car ahead did. The driver behind them is later still. Each car adds a bit, until someone stops completely.

The jam moves backward

Cars leave the front of the jam while new ones join at the back, so the jam itself drifts upstream at around 15 to 20 km/h. Drivers far behind hit a wall long after the first driver sped up again.

A gap soaks it up

A driver with room ahead can ease off gently and let the gap shrink instead of braking. The wave dies there, and everyone behind them keeps rolling. A few such drivers are enough to calm a whole road.