# Closing of a Lane and Simulation of Speed limits |

In this scenario you can simulate an open system with a lane closing (e.g., due to road works) at the position of the white squares. You can observe the remarkably positive effect of a more homogeneous vehicle population introduced by a speed limit.

- In the initial setup, a speed limit of 80 km/h is imposed. This affects only cars since trucks have a maximum speed of 80 km/h anyway (at least in this simulation...) No breakdown occurs!
- Now increse the speed limit or lift it, corresponding to a limit of 140 km/h in this simulation, and leaving constant the influx of vehicles. Althoug the theoretical (static) capacity has increased by this action, some vehicles no longer manage to change to the free lane which sooner or later provoques a breakdown! The dynamics of the resulting traffic jam is similar to the on-ramp scenario 2.
- Decreasing the speed limit below 80 km/h also leads to breakdowns, so there is some optimal value for the limit!

So, "unfortunately", speed limits may be useful, but only, if

- there is heavy traffic,
- there is a bottleneck.

Otherwise,a local speed limit can act as the bottleneck and provoque breakdowns by itself!