On vehicles wider than 80 inches, the primary two systems of marker lights are clearance marker and identification lights. The clearance marker lights are the two outermost fixtures on the cab, which are used to identify the outer edges of the vehicle's body.

Marker lights are identification lights designed to tell other motorists on the road that a large vehicle is ahead. And for a long time, fire apparatus manufacturers have been responsible for the spacing and configuration of marker lights.

: one of the usually colored lamps on the left and right of the front and rear of a truck that indicate the extreme sides of the vehicle.