Third rail
Electrification was installed from Sunnyside Yard in Queens, through New York Penn Station to Manhattan Transfer station in New Jersey. A third rail (Top Contact) system was used. Electrification was later changed to overhead catenary, when the PRR electrified its mainline to Washington, D. C. in the early 1930s. Third rail is still installed in the East River Tunnels in order to provide power the LIRR trains. Third rail is also installed in the North River Tunnels for use in emergencies should power be lost to the overhead catenary.