Interpreting Congestion Charge (Simple, step 1)
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WHAT IS IT?
While at first sight, the purpose of the model may appear to be to test congestion charge as a policy, the underlying idea is illustrate how the same model may be interpreted differently by selecting and weighing some data over other.
The model illustrates the indeterminacy of the concept of public goods, based on Michael Feeden's (pp. 128-30, 2005) example.
HOW TO USE IT
Click 'Setup' to generate a population of 1000 with incomes ranging 1-100. By clicking 'Go' each person will decide whether to take the car or go by bus that day.
By sliding the 'Congestion charge cost' slider, you can increase or decrease the price of congestion charge.
EXTENDING THE MODEL
The price sensitivity part of agents' decision is also simplified, and the amount of extra traffic per vehicle on the road is linear (when it should probably be exponential), etc.
Michael Freeden mentions the possibility of building more roads in his discussion of the example. This could also be a possible extension to the model.
Lastly, sliders or other ways for the user to manipulate these variables could be introduced:
avg-passengers-per-bus: 32
pollution-per-bus: 50
pollution-per-car: 7
avg-passengers-per-car: 1.2
population: 1000
CREDITS AND REFERENCES
This model was built by Arthur Hjorth (arthur.hjorth@stx.oxon.org) and released under Creative Commons Attribution-NonCommercial-ShareAlike 3.0 (http://creativecommons.org/licenses/by-nc-sa/3.0/)
It is based on an example by Professor of Ideology Michael Freeden.
Freeden, M. What Should the "Political" in Political Theory Explore?. Journal of Political Philosophy, vol. 13 (2005), 113-134
Comments and Questions
;; Interpreting Congestion Charge ;; ;; This model is based on Michael Freeden s example ;; The purpose of this model is to show the ambiguity of political concepts such as public goods ;; and the interpretation of policies. ;; TODOS: price sensitivity globals [ global-pollution-per-day ;; pollution variable travel-time-added ;; traffic congestion, how congested is traffic. ;; this variable adds itself to a vehicle s travel time average-travel-time ;; average travel time calculated per day per person yesterdays-travel-time-added ;; the average travel time added per vehicle yesterday ;; this is key in people s decision making process for whether they want ;; to go by car or bus. turtles-driving ;; number of turtles driving on any day median-income-drivers ;; the median income of turtles who drive median-income-bussers ;; the median income of turtles who take the bus cars ;; number of cars busses ;; number of busses median-income-preference-met ;; median income for those whose transport preference was met median-income-preference-not-met ;; median income for those whose transport preference was not met turtles-preference-met ;; number of people whose prefernces are met turtles-preference-not-met ;; number of people whose preferences are not met avg-passengers-per-bus pollution-per-bus pollution-per-car avg-passengers-per-car population ] turtles-own [ income ;; income level of turtle, 1-100 car-love ;; how much the person wants to drive their car, 1-100 willing-to-wait ;; how willing the person is to spend extra time on travelling by car ;; rather than travelling by public transport, 1-100 wishes-to-drive? ;; would this person ideally drive today? can-afford-to-drive? ;; can this person afford to drive today will-drive-today? ;; will this person actually drive today preference-met? ;; true if person travels by preferred medians ] ;;; ;;; SETUP PROCEDURES ;;; to setup ;; clean up reset-ticks clear-all set avg-passengers-per-bus 32 set pollution-per-bus 50 set pollution-per-car 7 set avg-passengers-per-car 1.2 set population 1000 ;; create population create-turtles population [ ;; setting shape person set shape "person" ;; placing randomly on map in unoccupied location move-to one-of patches with [any? turtles-here = false] ;;move-to first patches with [any? turtles-here = false] ;; setting income randomly (will be changed as part of gini coefficient implementation) set income random 99 ;color-turtle set color white set car-love random 99 set willing-to-wait random 99 ;; adding 1 to all turtle properties to avoid divide by zero errors. Look up how to set a range for random and correct this. set income income + 1 set car-love car-love + 1 set willing-to-wait willing-to-wait + 1 ] end to go ;; switch over yesterdays time travel set yesterdays-travel-time-added travel-time-added ;; ask all turtles to decide on going by car or not ask turtles [decide] ;; calculate number of cars and busses calc-vehicles ;; calculate the time delay created by number of cars calculate-delay-created ;; calculate median incomes for respectively drivers and non-drivers calculate-median-incomes ;; calculate how many turtles traveled by their preferred medians calculate-preference-met ;; calculate median income for those who traveled by preferred and those who did not. calculate-median-preference-met calc-pollution end to calc-vehicles set cars count turtles with [will-drive-today? = true] / avg-passengers-per-car set busses count turtles with [will-drive-today? = false] / avg-passengers-per-bus end to calculate-median-incomes ifelse any? turtles with [will-drive-today? = true] [ set median-income-drivers median [income] of turtles with [will-drive-today? = true] ] [ set median-income-drivers 0 ] ifelse any? turtles with [will-drive-today? = false] [ set median-income-bussers median [income] of turtles with [will-drive-today? = false] ] [ set median-income-bussers 0 ] end to calculate-preference-met set turtles-preference-met (count turtles - count turtles with [wishes-to-drive? = true and will-drive-today? = false]) set turtles-preference-not-met population - turtles-preference-met end to calculate-median-preference-met ;; if clause to avoid null pointer exc ifelse any? turtles with [(wishes-to-drive? = true and will-drive-today? = true) or wishes-to-drive? = false] [ set median-income-preference-met median [income] of turtles with [(wishes-to-drive? = true and will-drive-today? = true) or wishes-to-drive? = false] ] [ set median-income-preference-met 0 ] ;; if clause to avoid null pointer exc ifelse any? turtles with [wishes-to-drive? = true and will-drive-today? = false] [ set median-income-preference-not-met median [income] of turtles with [wishes-to-drive? = true and will-drive-today? = false] ] [ set median-income-preference-not-met 0 ] end ;to color-turtle ; ;; coloring people per income ; ;; dark red for lowest quartile, pink for next, light blue for next, dark blue for highest quartile ; if income <= 25 ; [ ; set color 15 ; ] ; if income > 25 and income <= 50 ; [ ; set color 17 ; ] ; if income > 50 and income <= 75 ; [ ; set color 95 ; ] ; if income > 75 ; [ ; set color 105 ; ] ;end to calc-pollution ;; calculates pollution by multiplying pollution per car with no of cars and ditto for busses set global-pollution-per-day cars * pollution-per-car + busses * pollution-per-bus end to calculate-delay-created ;; calculates delay created by finding sum of vehicles. All vehicles cause same amount of delay which probably isnt true... set travel-time-added (cars + busses) end to decide ;; turtle procedure. Decide on whether to drive that day or not. would-prefer-car can-afford-to-drive will-drive end to would-prefer-car ;; this determines if the turtle would ideally drive ifelse (car-love - (yesterdays-travel-time-added / willing-to-wait)) > 0 [ set wishes-to-drive? true ] [ set wishes-to-drive? false ] end to can-afford-to-drive ;; this determines if the turtle can afford to drive. This needs to be tweaked to take into ;; consideration feedback effect from congestion charge lowering price of public transp ifelse congestion-charge-price / 2 > income [ set can-afford-to-drive? false ] [ set can-afford-to-drive? true ] end to will-drive ;; this determines if the turle will actually drive ifelse wishes-to-drive? and can-afford-to-drive? [ set will-drive-today? true set shape "car" ] [ set will-drive-today? false set shape "bus" ] end
There is only one version of this model, created about 14 years ago by Arthur Hjorth.
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