NetLogo User Community Models

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## WHAT IS IT?

This model makes the Braess Paradoxon visible with an agent-based approach.

## HOW IT WORKS

The agents try to minimize their traveling time from the "city" on the left to the "city" on the right. They have two or three choices, depending on whether the middle road is blocked or not.

The thick roads are highways. Overtaking is allowed as they have a much higher capacity, but they are longer than the roads. The roads are shorter, but no overtaking is allowed, so a car might lose some time behind a slower car.

## HOW TO USE IT

You can start with all three options available, let the model run to get to a steady traveling time (ideally in the Nash-Equilibrium) and then block the road to see an increase in traveling time. This works best with the default parameters of:

150 vehicles
5 memory-size
1.5 highway-length

## THINGS TO NOTICE

Notice how the traveling time changes to a faster time with less options available.

## THINGS TO TRY

Try different numbers of vehicles to get a feeling how much traffic is necessary to make the effect visible.
One can also try to use different lengths of the highways around. At a certain highway length, turtles quickly learn that the normal roads are always the better option.

## EXTENDING THE MODEL

One can extend the model by
- having different strategies for the turtles to determine the fastest route
- make the road-blocked button work in both directions during the simulation (there's a bug when you switch from on to off)
- make the highways have different lengths
- ...

There are many ways to extend the model. Feel free to play around!

## NETLOGO FEATURES

none

## RELATED MODELS

traffic two-lanes

## CREDITS AND REFERENCES

made by Juergen Reiter in June 2019