It is obligatory to fit Extremity (width) side lights:

1. Correct answer: On a 210cm-or-more wide vehicle.
2. Only on connected vehicles or semi-trailers.
3. On all commercial vehicles.
4. On vehicles with an all up width of 180cm or less.

WhyWidth marker lights are fitted to vehicles 210 cm wide or more. They show oncoming drivers how wide the vehicle is.