Cinzia Bassi, Paola Corradetti, Angela Recchia

Computer Science and Simulation for Economics

Project work on

"Public investment benefits."


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created with NetLogo

view/download model file: public_investment_benefits.nlogo


We suppose that Local Administration has a traffic problem: there's a lake which creates an obstacle for cars. They have to take a longer road to go from a point to another point. L.A. could build a bridge over the lake in order to allow cars to reach the target point faster, but it has a cost.
L.A. has to decide what is more convenient:
- to build the bridge
- not to build the bridge


In order to determine whether building the bridge is convenient, two kind of turtles (=cars) are created.
We defined the cars that travel around the lake as "old way cars" and the cars that cross the bridge as "new way cars".
Each car has his own speed. They can accelerate or decelerate. It depends if they are preceded or not from other cars, because they can't exceed each other.


First we have to decide how many cars we want, using the sliders NUMBER NEW WAY CARS and NUMBER OLD WAY CARS.
Then, when we click on SETUP the scene is created: two street, the lake and cars.
The simulation starts when we press GO. It's possible to modify the car speed by the sliders SPEED UP and SLOW DOWN. The time value, investment cost and toll are chosen respectively by sliders TIME VALUE, INVESTMENT COST and TOLL.
Monitors show you:
- average speed of cars that are running on the old way and on the new one (AVERAGE SPEED OLD WAY CARS and AVERAGE SPEED NEW WAY CARS);
- average time of cars that are running on the old way and on the new one (AVERAGE TIME OLD WAY CARS and AVERAGE TIME NEW WAY CARS);
- difference in times to complete the two ways (DIFFERENCE TIME);
- gain/loss coming from building the bridge and from the different times to run through the two ways (GAIN/LOSS);
- average rent of drivers which is resulted by the difference between their availability to pay and the toll amount that they pay in reality (AVERAGE RENT).

The graphs on the right part represent the dynamic of average speed and of avarage time of the two different groups of cars and the consequent cost/benefit.


When the number of new way and old way cars is different, is it a generally true that the time used to run through the less busy way is inferior than the time used to run through the other way?

What does happen to the speed?

Which of the two groups is the most sensitive to variations of acceleration and deceleration?


It would be interesting and worth of trying to modify the values of the sliders relating to:
- the number of the old way and new way cars in order to analyze different scenarios about traffic over-crowding;
- the time value and the investment cost in order to make different cost/benefit analysis;
- the toll in order to obtain different values of driver's rent.


The model can be improved by using a safe distance between cars and by letting drivers choose the way that they prefer.
In order to have a more complete cost/benefit analysis, we could build new ways of different lenghts going around the lake.


This simulation is inspired to:

- " Traffic Basic "
- " Traffic 2 Lanes "

both taken from NetLogo Models Library


This model was created for the course of “Informatica e Simulazione per l'Economia” (2006-2007) by Professor Pietro Terna, Faculty of Economics, University of Turin.