Is it allowed for people to ride on the outside of your vehicle, such as in a pick-up truck, if there is no space inside?

• Yes, it is allowed.
• Yes, it is allowed and preferred.
• No, only if there is traffic.
• No, it's not allowed at all.
  Explanation:

  "Riding on the outside of a vehicle, including the open box of a pick-up truck, is prohibited. Both the driver and the passenger can be charged for this offence."