Final answer:
When a load extends over 4 inches beyond the side of a vehicle, it must be marked with an amber combo clearance and side marker lamp for safety.
Step-by-step explanation:
You are asking about regulations pertaining to vehicle lighting for oversized loads. According to the Federal Motor Carrier Safety Regulations, any load that extends beyond a certain length must have additional lighting to indicate its size. Specifically, any load that extends more than 4 inches beyond the side of the vehicle should be marked with an amber combo clearance and side marker lamp on the side of the projection. This is to ensure visibility and safety on the roads for both the oversized load vehicle and other road users. Keep in mind that regulations may vary by state, so it is always important to check local guidelines.