What is the purpose of amber clearance lamps on a truck-tractor?

Amber clearance lamps on a truck-tractor are designed to enhance visibility during low light conditions. Their primary function is to make the vehicle more noticeable to other drivers, particularly in situations where visibility might be limited, such as at dusk, dawn, or in inclement weather. These lamps are part of a vehicle's overall lighting system that helps define its size and shape, which is crucial in preventing accidents by alerting other drivers to the presence of the truck-tractor.

While the other options may suggest alternative functions, they do not accurately represent the crucial role of the amber clearance lamps. For example, while these lamps may contribute to indicating vehicle dimensions, they are not specifically meant to signal turning; they are not limited in their utility only to daytime driving; nor are they included purely for aesthetic reasons, as their design and requirement are rooted in safety regulations.