Which vehicles should you not pass?

• When it has stopped for a pedestrian crossing the road
• At a railway crossing
• When the traffic in front slows down unexpectedly
• All of the above
  Explanation:

  "a vehicle that has stopped for a pedestrian crossing the road • near or at the crest of a hill • just before or within an intersection • at a railway crossing • on a curve or any place where the view ahead is obstructed • on the shoulder of the road • when the traffic in front is slowing down unexpectedly."