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## NetLogo User Community Models

WHAT IS IT?

The Netlogo model simulates the behaviour of drivers in a typical car park, which has a default parking capacity of 48 lots (this value corresponds to the default value of the allowance slider bar). The user can change the allowance value, preferably to a higher value, to see whether this produces any positive effect; for example, a significant decrease in the percentage (%) of unhappy drivers.

There are a total of 6 lanes, which are arranged from 1-6, with lane 6 nearest to the point of entrance and lane 1 nearest to the point of exit. 16 lots are located between 2 lanes, i.e. 16 lots between lanes 1 and 2, another 16 lots between lanes 3 and 4 and another 16 lots between lanes 5 and 6. There will also be lane A and B (perpendicular to lane 1-6), which allows the cars to turn. The speed limit is set by the user, ranging between 0-3m/s. The “rate-cars-enter” indicates the rate at which cars intend to enter the car park. Due to the restriction of vacant lots, not all the cars that want to enter the car park will be allowed to.

The traffic light, located at the entrance is, by default, automatically monitored, and will turn GREEN when there are lots available. The traffic light will turn RED if the number of cars in the car park exceeds a certain number, namely, the maximum capacity of the car park. This means that no car will be allowed to enter, for as long as there are no cars whose duration of parking has expired. However, at times, even when the traffic light has been manually set to red, a few cars will still enter the car park. This is because these cars have already entered the park, but are queuing up. When this occurs, i.e. the car park is full and there are still cars willing to enter the car park, the traffic light will turn red and BLINK. There will be 1 point of ENTRY and 1 point of EXIT, for cars to enter and leave, respectively. Cars will drive into lanes 1-6 with a probability of 0.5. An optional diversion into lanes 2, 3, 4 and 5 occurs at the probability of 1.5/3, 1/3, 1.5/3 and 1/5, respectively, if the cars are unable to find an empty lot after 1 complete round around the car park.

HOW TO USE IT AND HOW IT WORKS

1) The Setup button initializes the model. Three rows of parking lots are created. Each row of parking lots is comprised of 16 empty lots for the cars to be parked. The arrows will show the direction that the cars will be moving. The two green arrows represent the entrance and exit of the car park.

2) The Go button starts the entry of the cars, which will move around the car park, in search of an empty lot to park. Different cars will park at different rows of the car park in different probability.
3) The Start-Plotting button will allow the user to start the plotting of the graph to obtain information on the car park data.

4) The Start-Averaging button must be used concurrent to the “Start-Plotting” button. This function will start to plot the graph to find the percentage of unhappy drivers, the usage of the car park lots, as well as the average waiting time to find an empty parking lot.

5) The Switch button is to allow the users to control the volume of cars entering the car park. Users may notice that, sometimes, even when the traffic light has been manually set to red, a few cars will still enter the car park. This is because these cars have already entered the car park and are queuing up. When the car park is full, and there are still cars that are willing to enter the car park, the traffic light will BLINK. This indicates that there are still cars willing to park. By default, the traffic light is automatically monitored. In order for the “Switch” button to function, the user has to switch the “Manual-Traffic-Light” from “false” to “true”.

6) The Manual-Traffic-Light allows users to manually control the number of cars entering the car park.

Monitors:
7) The Clock (min) represents the time steps, in minutes.

8) The Total-Num-Cars represents the total number of cars present in the car park.

9) The Num-free-Parking-Lots represents the number of empty parking lots available in the car park.

10) The Park-Usage (%) represents the percentage of the car park lots being taken up or used.

11) The Percent_Unhappy (%) represents the percentage of unhappy drivers.

12) The Ave waiting_time refers to the average waiting time for a driver, before finding an empty lot and parks.

13) The Percent_exiting (%) refers to the percentage of cars that leave the car park, with or without parking.

Slider bars:
14) The Ave_Parking_Duration (minutes) represents the average time the drivers will park before leaving the car park.

15) The Speed represents the speed of the cars in m/s.

16) The Max_Allowance represents the maximum number of cars that are allowed in the car park at any one time.

17) The Ave_Rate_Cars_Enter represents the rate at which cars intend to enter the car park, per min. This is because not all the cars that intend to enter the car park are allowed to do so. The traffic light at the entrance will turn red when the number of cars in the car park exceeds a certain number. Thus, no car will be allowed to enter as long as there is no car whose duration of parking has expired.

18) The Ave_Patience_Level represents the patience level of the drivers. It is expressed in units.

Graphical Plots:
19) The Graph plots the % of unhappy car users, the % usage of the carpark lots and the average waiting time in order for a car park user to find an empty lot.

THINGS TO NOTICE

In the simulation , the cars may appear to be colliding at some points. This is because the patches are set very small (and this was done to have a high graphic resolution of the patches).

The variables that the user can vary are the “average parking duration”, “speed”, “rate of cars entering”, the “maximum allowance” and the “average patience level”. These variables allow the user to toggle with different scenarios of drivers’ behaviour in the car park.

CREDITS AND REFERENCES

AUTHOR OF THE SIMULATION:
Umeyr Kureemun,
a first year undergraduate student at the National University of Singapore.

www.umeyr.50megs.com
(This webpage is actually under construction)

The description of the model was done mainly by Miss. Kee Guek Ling Deborah.