Eight grade crossing island detection technologies designed to eliminate problems associated with loss of shunt were evaluated by engineers at Transportation Technology Center, Inc., a subsidiary of the Association of American Railroads, Pueblo, Colorado. Performance of these alternative technologies was compared to that of a standard track circuit and an independent sensor. Conventional track circuits can be susceptible to non conductive films on rails and wheels resulting in unreliable shunt and operation of crossing warning devices. Alternative technologies, which include enhanced track circuits and non-contact sensors, are designed to determine when a train occupies and departs the grade crossing island limits. Screening tests conducted at the Transportation Technology Center were designed to evaluate the effect of parameters such as train switching, speed, wheel load, induced electrical ground return current, and other items on the reliability of these alternative technologies. Three technologies were ultimately selected for field reliability testing.