Which of the following vehicles requires chains and flags (perimeter lighting)?

1. A vehicle carrying a dust-creating material.
2. A vehicle carrying hazardous materials.
3. Correct answer: A trailer and a semi-trailer that don’t have a floor and walls.
4. A vehicle carrying steel cylinders.

WhyChains and flags at the sides are needed on trailers and semi-trailers without a floor and walls. They show the vehicle's outline when the freight is long.