Abstract
The San Diego Light Rail Transit System is a direct current powered rapid transit system installed in an area which has had no stray traction power source since 1950. The Metropolitan Transit Development Board has recognized its responsibility to existing utilities which have limited options in protecting their structures (many of them electrically discontinuous) from the effects of stray traction currents. The Board and its corrosion consultant have organized an underground corrosion control committee. Field investigations and computer simulations have been conducted to determine the extent of anticipated stray current effects. Field testing included soils investigation, track continuity and track-to-earth resistance measurements. Because the running rails serve as the negative return system of the traction power circuit, track-to-earth resistance is a major factor in the magnitude of stray current effects. Recommendations have been made to limit stray currents at the source by improving the electrical isolation characteristics in several areas. This includes separation of the embedded track section from the tie and ballast section, isolation of the maintenance/storage yard from the mainline track, and rebuilding selected grade crossings. Testing programs to evaluate stray current effects on transit structures and nearby utilities are progressing in an atmosphere of cooperation.
