Final answer:
Clearance lights are required by law for trucks or buses to increase visibility and indicate the vehicle's width. The specific width of these lights may vary according to regulations.
Step-by-step explanation:
In accordance with the law, trucks or buses are required to have clearance lights. These lights serve to increase the visibility of the vehicle and indicate its width.
The width of the clearance lights varies depending on the specific regulations of the particular jurisdiction. However, a common requirement is to have lights on both sides of the vehicle, positioned as wide apart as the outermost points of the vehicle, including any protrusions such as mirrors or fenders.
It is important for drivers of trucks or buses to ensure that their clearance lights are working properly and comply with the applicable laws and regulations to promote safety on the road.