Conduit Current Collection - Usage

Usage

Conduit current collection was one of the first ways of supplying power to electric tramcars but it proved to be much more expensive, complicated and trouble-prone than overhead wires. When electric street railways became ubiquitous, it was only used in those cities which did not permit overhead wires. These included London, Paris, Berlin, Marseilles, Budapest and Prague in Europe and parts of New York City and Washington DC in the United States.

In Denver, Colorado, the world's second electrically operated street railway, starting in 1885, pioneered the use of conduit current collection. Difficulties with the conduit and the electric streetcars led to the replacement of all conduit cars and lines with cable cars by 1888.

New York City had the largest installation of conduit cars, due to the prohibition of stringing overhead wires on Manhattan Island, although a few Bronx-based trolley lines entered the northern reaches of Manhattan using overhead wire. Trolley lines from Brooklyn and Queens also entered Manhattan under wire, but did not use city streets. The primary reason for the initial adoption of the conduit "plow" in Manhattan was the fact that return currents from conventional overhead wires using track return grounds were eroding gas mains.

The expense of creating conduit lines in New York was reduced to where it was possible to convert the cable vaults from discontinued cable car lines to conduit use. The huge expense of building new conduit, however, gave New York the distinction of having one of the last horsecar lines (the Bleecker Street Line) in the U.S., not closing until 1917. (Pittsburgh actually ran the very last U.S. horsecar, with service ending finally in 1923.)

In some old photographs, two "slots" may be seen between the rails. In New York City, sometimes one slot was used for a cable line and the other for electrical purposes. Occasionally, two competitive lines would share a common track and would have independent slots for the ploughs of the respective cars.

In New York City, the Queensboro Bridge between Manhattan and Queens had tracks installed on the outer lanes with conduit, for Manhattan cars in addition to overhead wire. The conduit allowed them to run to Queens Plaza terminus without need for removing the plough and raising the poles. In later years the conduit was removed and only trolley wire remained.

In the centre of Brussels, a number of tram lines were fitted with conduit, the last ones being converted to overhead operation during World War II.

The system was tried in the beachside resort of Blackpool, UK (see Blackpool tramway) but was soon abandoned as sand and saltwater was found to enter the conduit and cause breakdowns and there was a problem with voltage drop. Some sections of tramway track still have the slot rails visible.