Child of Traffic Basic

globals [max-speed traffic-density road-patches]

turtles-own [ speed ]

to setup
  clear-all
  set-patch-size 20
  setup-globals
  setup-patches
  setup-cars
end 

to setup-globals
  set max-speed 1
  set traffic-density 0.3
  set road-patches patches with [pycor = 0]
end 

to setup-patches
  ask road-patches [set pcolor white]
end 

to setup-cars
  let num-cars round (traffic-density * count road-patches)
  ask n-of num-cars road-patches [sprout 1]
  ask turtles [
    set color yellow
    set heading 90
    set speed random-float 1
    ]

  ask one-of turtles [
    set size 2
    set color red ]
end 

to go
  ask turtles [
  change-speed
  forward speed ]
  wait 0.1
end 

to change-speed
  let hindrance one-of turtles-on patch-ahead 1
    ifelse (hindrance != nobody)
    [ set speed 0.80 * [speed] of hindrance ]
    [ set speed (1.1 * speed) ]
    if speed > max-speed [
    set speed max-speed ]
end