Despite substantial reductions in accidents at highwayrailroad intersections over the past decade, such accidents remain a major cause of fatalities and injuries related to railroad operations. Accordingly, both highspeed and freight railroads, as well as local, state, and federal highway agencies and the Federal Railroad Administration are interested in innovative, low-cost alternatives to conventional grade crossing warning systems. A key component for such systems is the technique for detecting the presence of approaching trains to activate warnings such as flashing lights and gates. Conventional systems rely on the shunting of track circuits by approaching trains for such activation. However, track circuits are expensive to install and maintain, and are not 100% reliable under conditions of rail contamination or light-weight rolling stock. Moreover, as conventional train control systems are replaced by communications-based train control systems, track circuits will no longer be required for activation of train control signals. This has resulted in a search for alternatives to conventional track circuits to detect train presence. The objective of this project is a low-cost, reliable alternative to conventional track circuits for activating grade crossing warning systems.