Clearance lamps and marker lights are lighting devices for the purpose of indicating the width and height of a vehicle. The ability to identify the size and type of vehicle is necessary to maintain safety on our roads and highways. Clearance lamps are installed at the front or rear of a vehicle near the upper left and right extreme edges to indicate the overall width and height of the vehicle. They provide a ready indication of whether or not the vehicle can drive under a low ceiling structure, such as a bridge or a loading dock canopy. Side marker lamps indicate the presence of a vehicle when seen from the front and sometimes serving to indicate its width. When seen from the side they may also indicate its length. Marker lamps provided on the rear end of an automobile incorporate tail lamps for displaying the rear end of the vehicle, stop lamps which illuminate in conjunction with braking action, tail-and-stop lamps made by integrating the stop lamps and the tail lamps, and rear fog lamps. The marker lamps convert white light from a bulb into red light. These lamps are an important factor in the safe operation of trains and must meet up with specific performance requirements. Clearance lights must be distinctive, i.e., easily recognized, and ought to be properly defined in terms of light intensity, distribution and color. In addition, marker lights must be easy to maintain or replaced as they are required to be inspected and checked for performance periodically. A typical marker lamp assembly comprises an incandescent light bulb that is encased inside a small housing. A colored lens, typically an amber lens, forms the outer wall of the housing. The ongoing transition from incandescent light sources to light emitting diode (LED) light sources has made clearance lamps smaller and more power efficient.
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