velocity

globals [
  sample-car
]

turtles-own [
  speed
  speed-limit
  speed-min
]

to setup
  clear-all
  ask patches [ setup-road ]
  setup-cars
  reset-ticks
end 

to setup-road ;; patch procedure
if pycor < 2 and pycor > -2 [ set pcolor white ]
end 

to setup-cars
  set-default-shape turtles "car"
  create-turtles 1 [
    set xcor random-xcor
    set heading 90
    ;; set initial speed to be in range 0.1 to 1.0
    set speed 0.1 + random-float 0.9
    set speed-limit number-of-speed
    set speed-min number-of-speed

  ]
  set sample-car one-of turtles
  ask sample-car [ set color red ]
end 

; this procedure is needed so when we click "Setup" we
; don't end up with any two cars on the same patch

to go
   ask turtles [
    let car-ahead one-of turtles-on patch-ahead 1
     ;; don't slow down below speed minimum or speed up beyond speed limit
    if speed < speed-min [ set speed speed-min ]
    if speed > speed-limit [ set speed speed-limit ]
    fd speed
  ]
  tick
end