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.
A state-of-the-art microwave system is used to determine the presence, position, velocity, and direction of movement of trains for activation of highway grade crossing warning systems. The ranging sensor uses frequency modulated continuous wave (FMCW) processing to determine the distance of trains from the crossing (within a frequency range of 24.35 to 24.7 GHz), and Doppler processing to measure train velocity. The ranging sensor has a power output of .005 watts, a range of about 1 mile, and a range resolution of 2 feet. The velocity sensor is a Doppler module radar operating at 24.125 GHz with a power output of .005 watts and a range of 1 mile. It is capable of detecting closing or receding velocities from 0.5 mph up to 150 mph.
