The diagram shows a portable warning triangle. The warning triangles MUST be used:

• A. When you break down, your vehicle weighs more than 12 tonnes laden and it is not visible for 200 metres.
  Explanation:

  "Large vehicles stranded on the side of the road create sizeable objects for other motorists to negotiate. Ensure that your vehicle can be seen by using a warning triangle where necessary."
• B. When you break down, your vehicle weighs less than 12 tonnes and you are on a road without street lights.
• C. When you break down regardless of the size of your vehicle.