The Indeterminacy of 'Public Goods' - framing an analysis of a congestion charge policy

;; 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
  
  color?                                 ;; color code boolean
  
  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 1.5
  set population 1089
  
  set color? false
  
  


  ;; create population
  create-turtles 1088
  [
    ;; 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
    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
  ]
  
    create-turtles 1
  [
    ;; setting shape person
    set shape "person"

    ;; setting income randomly (will be changed as part of gini coefficient implementation)
    set income random 99
    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 color-code
  ifelse color? = false
  [
    set color?  true
  ]
  [
    set color?  false
  ]
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
  ask turtles[
  ;; 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 white-turtle
  ask turtles
  [
    set color white
  ]
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-cost / 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