This report describes testing of prototype vehicle proximity alert system (VPAS) technologies, and presents and evaluates the results. The object was to determine the feasibility of VPAS for possible use in priority vehicles (i.e., emergency vehicles, school buses, vehicles carrying hazardous materials, and large trucks) to detect trains at highway-railroad grade crossings. VPAS can transmit visual and audible warnings to motorists. These warnings are designed to alert motorists in the vicinity of a grade crossing of the presence of a train approaching the crossing. Section 1072 of the Intermodal Surface Transportation Efficiency Act (ISTEA) required field testing of VPAS. The Federal Highway Administration (FHWA) in coordination with the Federal Railroad Administration (FRA) sponsored the testing. Prototype testing was conducted in January-April and November 1995 and in January 1996 at the FRA's Transportation Technology Center (TTC) in Pueblo, Colorado. Systems tested at the TTC demonstrated that the concept of VPAS for warning vehicles of a train's approach to a grade crossing is feasible, though none of the systems as tested was suitable for further testing.