What is needed on the side of a bus or trailer that is greater than 80 inches in width?

A bus or trailer that exceeds 80 inches in width must be equipped with an amber side marker lamp. This requirement is essential for ensuring visibility and safety on the road. The amber side marker lamp serves as a clear signaling device, indicating the width of the vehicle to other drivers, particularly in low-light conditions or inclement weather.

In situations where the vehicle's width exceeds 80 inches, these side marker lamps help to define the outline of the vehicle, allowing other road users to judge the dimensions more accurately and maintain a safe distance. This is particularly important for larger vehicles that may not be easily seen in the same way that smaller vehicles are, thereby reducing the risk of collisions.

Other options, such as having two amber reflectors or two red tail-lamps, do not specifically meet the legal requirements for marking the width of a vehicle. While reflectors are useful for visibility, they do not serve the function of directly indicating the width. Tail lamps are essential for signaling stops and turns but do not provide information about the vehicle's width.