Conduit current collection

Conduit current collection is an obsolete system that was used by some electric tramways to pass current to streetcars via a "conduit", a small tunnel under the roadway. Modern systems fall under the term ground-level power supply.

The system is primarily composed of a channel, or conduit, excavated under the roadway; the conduit is positioned either between the running rails, much in the same fashion as the cable for cable cars, or underneath one of the rails; a car is connected to a "plow" or "plough" that runs through the conduit and delivers power from two electric rails at the sides of the conduit to the car's electric motor. Plows were manually attached and detached from cars as they switched rail lines.

Conduit current collection systems were implemented as early as 1881 with the Gross-Lichterfelde Tramway.^{: Appendix I} It proved to be much more expensive, complicated, and trouble-prone than overhead wires. When electric street railways became ubiquitous, conduits were only used in those cities that did not permit overhead wires, including London, Paris, Berlin, Marseille, Vienna, Budapest, Prague, Manhattan, and Washington, D.C.. The Bordeaux and Washington conduit systems remained the last in operation until being decommissioned in 1958 and 1962, respectively.

For decades, "catenary-free" systems such as conduit current collection were not reintroduced because they didn't meet modern safety standards. Modern systems, called ground-level power supply, use a segmented rail flush with the surface of the road instead of a conduit, and the rail segments are only powered when an appropriate vehicle is over them. Alstom APS was the first modern commercial ground-level power supply system, first installed commercially in Bordeaux. The French government reports no electrocutions or electrification accidents on any tramway in France from as early as 2003 until as recently as December 31, 2021.