When is it illegal to pass a vehicle?

• When oncoming vehicles are at a good distance from your vehicle.
• When oncoming vehicles are going very slow.
• When oncoming vehicles are too close and you have doubts about safely completing the pass.
  Explanation:

  "Oncoming vehicles are too close. If you have any doubts about safely completing the pass, do not attempt to pass."
• When oncoming vehicles allow you to pass.