![KingswayUnderpass](https://upload.wikimedia.org/wikipedia/commons/3/33/KingswayUnderpass.jpg)
Conduit current collection is an obsolete system of
electric current
An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. The moving pa ...
collection used by some electric
tram
A tram (called a streetcar or trolley in North America) is a rail vehicle that travels on tramway tracks on public urban streets; some include segments on segregated right-of-way. The tramlines or networks operated as public transport are ...
ways, where the power supply was carried in a 'conduit' (a small tunnel) under the roadway. Modern systems fall under the term
ground-level power supply
Ground-level power supply, also known as surface current collection or, in French, ''alimentation par le sol'' ("feeding via the ground"), is a concept and group of technologies whereby electric vehicles collect electric power at ground level fro ...
.
Description
The power rails are contained in a conduit midway between and below the two surface rails on which the cars operate, in much the same fashion as the
cable
Cable may refer to:
Mechanical
* Nautical cable, an assembly of three or more ropes woven against the weave of the ropes, rendering it virtually waterproof
* Wire rope, a type of rope that consists of several strands of metal wire laid into a hel ...
for
cable car Cable car most commonly refers to the following cable transportation systems:
* Aerial lift, such as aerial tramways and gondola lifts, in which the vehicle is suspended in the air from a cable
** Aerial tramway
** Chairlift
** Gondola lift
*** Bi ...
s. The conduit contains two "T" section steel power rails of opposite polarity facing each other, about apart and about below the street surface. Power reached the car by means of an attachment, called a plough (US plow), that rode in the conduit beneath the car. The plough had two
metal shoes attached to springs that pushed sideways against the power rails. The plough was normally connected to a platform that could slide laterally to conform with variations in the placement of the conduit, for example in some areas there was a conduit for cable cars adjacent to the one for electric cars.
The current was carried by a flexible cable from the plough through the platform to the car's controller and
motor(s). The running rails are not part of the electrical circuit. In the United States, the cars were sometimes popularly but incorrectly called
trolleys but did not typically draw power through a
trolley pole
A trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" (electrified) overhead wire to the control and the electric traction motors of a tram or trolley bus. It is a type of current collector. Th ...
from an
overhead wire
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as:
* Overhead catenary
* Overhead contact system (OCS)
* Overhead equipmen ...
as (strictly defined) trolley cars do.
Usage
![Blackpool 4](https://upload.wikimedia.org/wikipedia/commons/9/9d/Blackpool_4.jpg)
Conduit current collection was one of the first ways of supplying power to trams 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 that did not permit overhead wires, including London, Paris, Berlin, Marseilles, Vienna, Budapest, and Prague in Europe, and the New York City borough of Manhattan and Washington, D.C. in the United States.
In
Denver, Colorado
Denver () is a consolidated city and county, the capital, and most populous city of the U.S. state of Colorado. Its population was 715,522 at the 2020 census, a 19.22% increase since 2010. It is the 19th-most populous city in the Unit ...
, the world's second
electric street railway in 1885 pioneered conduit current collection. Difficulties with the conduit and the streetcars led to the replacement of conduit cars and lines with cable cars by 1888.
New York City
New York, often called New York City or NYC, is the List of United States cities by population, most populous city in the United States. With a 2020 population of 8,804,190 distributed over , New York City is also the L ...
had the largest installation of conduit cars, due to the prohibition of overhead wires on
Manhattan Island
Manhattan (), known regionally as the City, is the most densely populated and geographically smallest of the five boroughs of New York City. The borough is also coextensive with New York County, one of the original counties of the U.S. state ...
, although a few
Bronx
The Bronx () is a borough of New York City, coextensive with Bronx County, in the state of New York. It is south of Westchester County; north and east of the New York City borough of Manhattan, across the Harlem River; and north of the New Y ...
-based trolley lines entered the northern reaches of Manhattan using overhead wire. Trolley lines from
Brooklyn
Brooklyn () is a borough of New York City, coextensive with Kings County, in the U.S. state of New York. Kings County is the most populous county in the State of New York, and the second-most densely populated county in the United States, be ...
and
Queens
Queens is a borough of New York City, coextensive with Queens County, in the U.S. state of New York. Located on Long Island, it is the largest New York City borough by area. It is bordered by the borough of Brooklyn at the western tip of Long ...
also entered Manhattan under wire, but did not use city streets. The primary reason for the initial adoption of conduit systems was for aesthetic reasons as an alternative to overhead wiring that was often objected to as being unsightly.
The expense of creating conduit lines in New York was reduced where it was possible to convert the cable vaults from discontinued cable car lines. The huge cost of building new conduits gave New York the distinction of having one of the last
horsecar
A horsecar, horse-drawn tram, horse-drawn streetcar (U.S.), or horse-drawn railway (historical), is an animal-powered (usually horse) tram or streetcar.
Summary
The horse-drawn tram (horsecar) was an early form of public rail transport, wh ...
lines (the
Bleecker Street Line
The Bleecker Street Line was a public transit line in Manhattan, New York City, United States, running mostly along Bleecker Street, Crosby Street, and Lafayette Street from the West 14th Street Ferry in Chelsea to the Fulton Ferry in the Financ ...
) in the
U.S.
The United States of America (U.S.A. or USA), commonly known as the United States (U.S. or US) or America, is a country Continental United States, primarily located in North America. It consists of 50 U.S. state, states, a Washington, D.C., ...
, not closing until 1917. (
Pittsburgh
Pittsburgh ( ) is a city in the Commonwealth (U.S. state), Commonwealth of Pennsylvania, United States, and the county seat of Allegheny County, Pennsylvania, Allegheny County. It is the most populous city in both Allegheny County and Wester ...
ran the last U.S. horsecar, 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 electric cars. Occasionally, two competing lines shared a common track and had independent slots for the ploughs of the respective cars. In
London
London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
, two slots were sometimes used on a single-track stretch in a narrow road so that cars in each direction used separate conduits. Known as twin-conduit track, examples were found in York Road, Wandsworth and London Street, Greenwich.
[Harley, Robert J. (2002). ''LCC Electric Tramways''. Capital Transport, pp.179-81. ]
In New York City, the Queensboro Bridge between Manhattan and Queens had tracks installed on the outer lanes with conduits for Manhattan cars in addition to overhead wires. 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 London, the
London County Council Tramways
The London County Council Tramways was an extensive network of public street tramways operated by the council throughout the County of London, UK, from 1899 to 1933, when they were taken over by the London Passenger Transport Board.
Acquisiti ...
experimented with ''side conduit'', where the conduit was in one of the side rails. This was tried along Kingsland Road between Bentley Road and Basing Place,
Hoxton
Hoxton is an area in the London Borough of Hackney, England. As a part of Shoreditch, it is often considered to be part of the East End – the historic core of wider East London. It was historically in the county of Middlesex until 1889. I ...
, but the stresses and strains of the weight of the cars weakened the conduit, so it was not tried elsewhere.
In the centre of
Brussels
Brussels (french: Bruxelles or ; nl, Brussel ), officially the Brussels-Capital Region (All text and all but one graphic show the English name as Brussels-Capital Region.) (french: link=no, Région de Bruxelles-Capitale; nl, link=no, Bruss ...
some tram lines were fitted with conduits, the last ones being converted to overhead operation during
World War II
World War II or the Second World War, often abbreviated as WWII or WW2, was a world war that lasted from 1939 to 1945. It involved the vast majority of the world's countries—including all of the great powers—forming two opposin ...
.
The system was tried in the seaside resort of
Blackpool
Blackpool is a seaside resort in Lancashire, England. Located on the North West England, northwest coast of England, it is the main settlement within the Borough of Blackpool, borough also called Blackpool. The town is by the Irish Sea, betw ...
, UK, but was soon abandoned as sand and saltwater entered the conduit and caused breakdowns and there was a problem with voltage drop. Some sections of track still had the conduit slot visible until the tramway was refurbished in 2012.
Hybrid installations
Washington, D.C.
)
, image_skyline =
, image_caption = Clockwise from top left: the Washington Monument and Lincoln Memorial on the National Mall, United States Capitol, Logan Circle, Jefferson Memorial, White House, Adams Morgan, ...
had a large network of
conduit lines, to avoid wires. Some lines used
overhead wires
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, trolleybuses or trams. It is known variously as:
* Overhead catenary
* Overhead contact system (OCS)
* Overhead equipmen ...
when they approached
rural
In general, a rural area or a countryside is a geographic area that is located outside towns and cities. Typical rural areas have a low population density and small settlements. Agricultural areas and areas with forestry typically are describ ...
or
suburban
A suburb (more broadly suburban area) is an area within a metropolitan area, which may include commercial and mixed-use, that is primarily a residential area. A suburb can exist either as part of a larger city/urban area or as a separate ...
areas. The last such line ran to
Cabin John, Maryland
Cabin John is a census-designated place and an unincorporated area in Montgomery County, Maryland, United States. Its original southern boundary encompassed a section of the Chesapeake and Ohio Canal (C&O) including locks 8–12, and the northern ...
. The current collector "plow" was mounted underneath the car on a fitting just forward of the rear truck on
PCC streetcar
The PCC (Presidents' Conference Committee) is a streetcar (tram) design that was first built in the United States in the 1930s. The design proved successful in its native country, and after World War II it was licensed for use elsewhere in the ...
s. It had two cables with female connectors on cables to attach to matching cables of the car's electrical system. A "plowman" was assigned at each changeover point from overhead trolley wire to conduit to remove the cable attachments to the car and stow the plow, which did not remain with the car and was reattached in an incoming car running on overhead wire. The lower section of the plow "board" was drawn by the moving car within the cavity of the conduit. Because of this usage, many of Washington's streetcars carried
trolley pole
A trolley pole is a tapered cylindrical pole of wood or metal, used to transfer electricity from a "live" (electrified) overhead wire to the control and the electric traction motors of a tram or trolley bus. It is a type of current collector. Th ...
s, which were lowered while operating in the central part of the city; when the cars reached a point where they switched to overhead operation, they stopped over a ''plow pit'' where the conduit plows were detached and the trolley poles raised, the reverse operation taking place on inbound runs. The 'pit' here has the meaning analogous to racing circuit pits rather than a depression in the road.
In the UK,
London
London is the capital and largest city of England and the United Kingdom, with a population of just under 9 million. It stands on the River Thames in south-east England at the head of a estuary down to the North Sea, and has been a majo ...
had a hybrid network of double-deck trams: overhead collection was used in the outer sections and conduit in the centre. At the changeover from conduit to overhead wire, at a change pit, the process was largely automatic. The conductor put the trolley pole onto the wire, and as the tram moved forward the conduit channel veered sideways to outside the running track, automatically ejecting the plough - the tram was said to be 'shooting the plough'. At the changeover from overhead wire to conduit the process was a little more complicated. The tram pulled up alongside a ploughman, who engaged a two-pronged plough fork over the plough in a short length of unelectrified conduit and into the plough channel underneath the centre of the tram. As the tram drew forward, the conduit channel moved under the tram, carrying the plough into position.
The process illustrated
/ref> The conductor pulled down the trolley pole and stowed it. The ploughman's job was a fairly skilled one because, if he failed to locate the plough fork correctly, it or the plough could jam in the plough channel and cause lengthy delays. Some tram designs required an extra carrier to be located with the plough and these frequently caused problems for ploughmen not used to the design (particularly if the tram had been diverted from its normal route).
New conduit track was laid in 1951 for the Festival of Britain, which commemorated the Great Exhibition
The Great Exhibition of the Works of Industry of All Nations, also known as the Great Exhibition or the Crystal Palace Exhibition (in reference to the temporary The Crystal Palace, structure in which it was held), was an International Exhib ...
of 1851. The last tram was withdrawn in June 1952 and virtually all the tracks had been removed by the 1970s, although a short section can still be seen at the entrance to the former Kingsway Tramway Subway.
Other European hybrid tramway networks included Paris, Nice, Lyon, Lille and Bordeaux in France; Berlin, Vienna and Budapest. In Paris, the conduit sections were frequently very short, requiring cars to change from overhead to conduit and back several times in one journey. The last conduit line in Paris closed in 1936, while the last Bordeaux conduit car ran in 1953. The conduit systems in Berlin, Vienna and Budapest were very short lived, being replaced by overhead wires before World War I.
See also
*Current collector
Electric current collectors are used by trolleybuses, trams, electric locomotives or EMUs to carry electrical power from overhead lines, electrical third rails, or ground-level power supplies to the electrical equipment of the vehicles. Those for ...
*Ground-level power supply
Ground-level power supply, also known as surface current collection or, in French, ''alimentation par le sol'' ("feeding via the ground"), is a concept and group of technologies whereby electric vehicles collect electric power at ground level fro ...
* Online Electric Vehicle
*Railway electrification system
A railway electrification system supplies electric power to railway trains and trams without an on-board prime mover or local fuel supply.
Electric railways use either electric locomotives (hauling passengers or freight in separate cars), ele ...
*Third rail
A third rail, also known as a live rail, electric rail or conductor rail, is a method of providing electric power to a railway locomotive or train, through a semi-continuous rigid conductor placed alongside or between the rails of a railway t ...
*Tramway tracks
Tramway track is used on tramways or light rail operations. Grooved rails (or girder rails) are often used to provide a protective flangeway in the trackwork in city streets. Like standard rail tracks, tram tracks consist of two parallel st ...
Notes
External links
Illustrated articles on London's conduits and the Kingsway Tram Subway.
{{DEFAULTSORT:Conduit Current Collection
Electric rail transport
Tram technology