# Simulation of an On-Ramp

This szenario demonstrates, how an on-ramp acts as a stationary bottleneck provoquing a traffic breakdown on the main road UPSTREAM of the on-ramp and FREE traffic downstream.

- With the initial settings, upstream propagating stop-and-go waves on the main road are triggered at the on-ramp region! The on-ramp acts as generator of the waves, but any other type of flow-restricting inhomogeneity ("bottleneck") could do the same. Now vary the traffic flows of the main road and the on-ramp.
- At an reduced inflow of 2000 veh./h, free traffic can be sustained for up to 20 min but sooner or later breaks down.
- At 1600 veh./h, no breakdown occurs, but an existing jam will not dissolve! This so-called hysteresis is the basis why traffic-control measures to prevent the breakdown have a huge application potential.
- On increasing the ramp flow to 800 veh./h, and decreasing the main flow to 1600 veh./h, observe a stationary localized traffic breakdown "pinned" at the ramp region. Only for higher inflows, the upstream front will propagate further upstream giving rise to an extended congested region!
- Play with the politeness factor and switching threshold to change the aggressivity of the ramp vehicles.