The research on locomotives had one issue to be resolved: how to maintain electrical contact between a moving streetcar and a stationary wire. Beginning in the early 1880s inventors worked hard to solve this problem. They developed three main types of systems: overhead, third-rail, and underground. Other inventors experimented with battery-powered streetcars.

The third-rail was feasible only to segregated places because exposed ground-level conductor posed an obvious threat to people and animals.

In 1888, Frank Sprague who was a naval officer had joined Edison’s company, completed what was then the world’s largest electric streetcar system, in Richmond, Virginia. Sprague’s system used an under-running trolley, a small grooved wheel that rode along the underside of the overhead wire while attached to a pole on top of the streetcar. A strong spring on the trolley pole kept the wheel firmly in contact with the overhead wire. The apparent success of the Richmond installation encouraged many street railroads in small cities and suburban areas to adopt the overhead trolley. Sprague is also known as the ‘father of electric traction’.