Much has been written to address various aspects of designing heavy-rail DC transit systems to minimize
stray current interference. Most modern heavy-rail DC transit systems are designed with ungrounded traction
power distribution systems to control stray current at the source. As a transit system ages, sustaining the stray
current mitigation near the as-constructed condition requires a coordinated effort that involves the transit
agency and operators of neighboring structures. This paper briefly discusses some design features of an
ungrounded traction power distribution system and the stray current that can be produced by DC transit
operations. Guidelines are then presented as tools for the development of a coordinated effort to meet the
challenges of sustaining effective stray current control.
Keywords: DC transit system, stray current, mitigation, traction power distribution, interference, track-to-earth
resistance, track-to-earth potential, coordinated effort, education, communication, cooperation