Overheight vehicle detection and warning system

A height clearance indicator and warning system for use on a thoroughfare in advance of overhead obstructions, such as overpasses, railroad tressels, overhead signs, and the like, which traverse the roadway and which become low clearance hazards for vehicles having a height greater than the clearance afforded by the obstruction, said indicator and warning system comprising:

• at least two light sources located on either side of the thoroughfare in advance of the overhead obstruction, said light sources being spaced from each other along the thoroughfare so that a vehicle approaching said obstruction will pass the light sources one at a time in sequential order, each of said light sources also being mounted at a height above the thoroughfare no greater than the clearance of the impending overhead obstruction;
• a number of light sensors equal to the number of light sources, each light sensor being paired with a respective light source and located across the thoroughfare in the vicinity of its respective light source, said light sensors being mounted at a height above the thoroughfare substantially equal to the height above the thoroughfare of said light sources;
• detector means for detecting when the light beams from respective light sources to corresponding sensors paired therewith have been momentarily broken;
• means for producing a signal when the detector means detects that the light beams from the respective light sources are, within a given, preset time period, broken in sequence starting from the light beam associated with the pair of light sources and sensors most remote from the overhead obstruction and ending with the light beam associated with the pair of light sources and sensors nearest said overhead obstruction;
• control means adapted to receive said signal and activate a visible electric sign indicating that the vehicle approaching said overhead obstruction is too high to clear the obstruction and warning the driver of the approaching vehicle to stop;
• and
• said means for producing a signal further operating to clear the detector means and thus reset the system to ready status when only a portion of and not all the light beams from the respective light sources are broken within the preset time period, and when the light beams are broken but not in proper sequence.