Motorway traffic jam: phantom jam, roadworks, emergency corridor

One kilometre of Swiss motorway from above, three lanes in each direction. Every vehicle is coloured by its speed: green = 120 km/h, yellow ≈ 60, red = standstill. Below, a space-time diagram records all vehicles of the lower carriageway – jams show up as red bands that travel against the direction of traffic.

Key points

Phantom jam — a single car brakes briefly. With gaps that are too small, every follower brakes a little harder – a jam appears out of nowhere.
Stop-and-go — at high density jam waves form by themselves. They travel backwards at about 15 km/h.
Roadworks — the right lane ends. Zip merging only right before the bottleneck: use both lanes to the end, then merge alternately.
Emergency corridor — already at walking pace: vehicles in the left lane move left, all others right. The ambulance drives through the corridor; without it, it gets stuck.

Rule of thumb

Jams often have no cause at the front: one brief braking manoeuvre with too small a gap is enough. Keeping distance (at least 2 seconds) and driving smoothly damps the waves.

Legal basis (as of 14 Oct 2026)

Art. 8 para. 1 VRV (SR 741.11) – keep right; para. 3 – passing on the right is allowed in parallel queues.
Art. 8 para. 5 VRV – zip merging: where a lane ends, merge alternately right before the bottleneck.
Art. 36 para. 6 VRV – with three or more lanes the leftmost may only be used by vehicles allowed to drive faster than 100 km/h (hence no trucks on the left).
Art. 36 para. 7 VRV – emergency corridor at walking pace or standstill, between the leftmost lane and the lane next to it.

Notes

Traffic model: Intelligent Driver Model (IDM) for car following, simplified MOBIL for lane changes. The road is a ring: vehicles leaving on the right re-enter on the left.
Controls: scenario buttons, density slider (vehicles per km and lane), ⏩ time-lapse (×3), and in the emergency-corridor scenario the “Form emergency corridor” switch.
Lanes are drawn wider than to scale so that the corridor is clearly visible.

Simplified model, not legal advice. The current legal text on fedlex.admin.ch is authoritative.

traffic jamphantom jamstop-and-gomotorwayemergency corridorzip mergeroadworkstraffic flowIDMVRV