Pacific Electric 104 runs along Echo Park Avenue. This mostly single track line was one of the last local lines that the PE operated. It used a unique signaling system at the passing sidings where upon entering the single track segments cars tripped an actuator on the trolley wire, lighting a red signal embedded in the street on the next passing siding for the cars running in the opposite direction. When the block was cleared, the signal would shine green, and the cars would depart the siding.
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