Trucks have clearance lights to notify other vehicles of the presence of a huge automobile on the road. 2 of these red lights, one on each of the vehicle's sides, are compulsory.  The truck’s cab might accommodate an additional light. These lights are primarily used to alert oncoming traffic that a truck or semi-truck is in the area. There are several applications for clearance lighting. When used at loading bays, they warn the public when a truck is bigger than all the other automobiles in the area. They also aid those from a distance in making out their primary shape. Given their uses, the Department of Transportation mandates those lamps on oversize vehicles. More specifically, large trucks (those measuring 80 inches or over in width) are mandated to have clearance lamps. For vehicles that aren't as big, these lights aren't necessary.  Considering their practicality, these lights are essential for road travelers' safety. Trucks that don't use them risk being fined and perhaps confiscated.