Clearance marker lights legally combine both the clearance and the side marker functions into a single lamp. This is done by mounting a lamp with a very wide light emission pattern on the upper corner of the vehicle. In order for these lamps to function properly, they must be mounted at a 45 degree angle.

Marker lights are designed to tell other motorists about the other vehicles on the road. They indicate things like vehicle size, vehicle shape, and direction of travel. Marker lights are a visual signature, which means they don't require a common language, the ability to read, or any special skillset to recognize.