Last updated Conduit for current collection between the rails of streetcars in Washington, D.C., 1939. Washington installed the system in 1895 and it remained in operation until 1962
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,[3] 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.[4] Plows were manually attached and detached from cars as they switched rail lines.[3]
Conduit current collection systems were implemented as early as 1881 with the Gross-Lichterfelde Tramway.[5]: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, Marseilles, Vienna, Budapest, Prague, Manhattan, and Washington.[6] The Bordeaux and Washington conduit systems remained the last in operation until being decommissioned in 1958[7] and 1962,[2] respectively.
For decades, "catenary-free" systems such as conduit current collection were not reintroduced because they didn't meet modern safety standards.[7] 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.[8][9] The French government reports no electrocutions or electrification accidents on any tramway in France from as early as 2003[10] until as recently as December 31, 2021.[10][11][12]
Also in 1885, a conduit system was used on Britain's first electric tramway in the seaside resort of Blackpool. The conduit was replaced with overhead electrification, as sand and saltwater entered the it and caused breakdowns, and there was a problem with voltage drop. However the line survives to this day as part of the Blackpool tramway, and some sections of track still had the conduit slot visible until refurbishment in 2012. Car 4 of the original conduit line also still survives, and is preserved at the National Tramway Museum in Crich, Derbyshire.[13]
New York City had the largest installation of conduit cars, due to the prohibition of 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 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 country's last horsecar lines: the Bleecker Street Line, which operated until 1917.
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, 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.[14]
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 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, but the stresses and strains of the weight of the cars weakened the conduit, so it was not tried elsewhere.[14]
In the centre of Brussels some tram lines were fitted with conduits, the last ones being converted to overhead operation during World War II.
Hybrid installations
Washington, D.C., had a large network of conduit lines to avoid wires, as required by an 1889 law. Some lines used overhead wires when they approached rural or suburban areas. The last such line ran to Cabin John, Maryland. The current collector "plow" was mounted underneath the car on a fitting just forward of the rear truck on PCC streetcars. 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 poles, 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 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.[15] 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 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.
A tram is a urban rail transit in which vehicles, whether individual railcars or multiple-unit trains, run on tramway tracks on urban public streets; some include segments on segregated right-of-way. The tramlines or tram networks operated as public transport are called tramways or simply trams/streetcars. Because of their close similarities, trams are commonly included in the wider term light rail, which also includes systems separated from other traffic.
An overhead line or overhead wire is an electrical cable that is used to transmit electrical energy to electric locomotives, electric multiple units, trolleybuses or trams. The generic term used by the International Union of Railways for the technology is overhead line. It is known variously as overhead catenary, overhead contact line (OCL), overhead contact system (OCS), overhead equipment (OHE), overhead line equipment, overhead lines (OHL), overhead wiring (OHW), traction wire, and trolley wire.
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 track. It is used typically in a mass transit or rapid transit system, which has alignments in its own corridors, fully or almost fully segregated from the outside environment. Third-rail systems are usually supplied from direct current electricity.
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. The use of overhead wire in a system of current collection is reputed to be the 1880 invention of Frank J. Sprague, but the first working trolley pole was developed and demonstrated by Charles Van Depoele, in autumn 1885.
Ground-level power supply, also known as surface current collection or, in French, alimentation par le sol, is a concept and group of technologies that enable electric vehicles to collect electric power at ground level instead of the more common overhead lines.
A pantograph is an apparatus mounted on the roof of an electric train, tram or electric bus to collect power through contact with an overhead line. The term stems from the resemblance of some styles to the mechanical pantographs used for copying handwriting and drawings.
A horsecar, horse-drawn tram, horse-drawn streetcar (U.S.), or horse-drawn railway (historical), is an animal-powered tram or streetcar.
A bow collector is one of the three main devices used on tramcars to transfer electric current from the wires above to the tram below. While once very common in continental Europe, it was replaced by the pantograph or the trolley pole, itself often later replaced by the pantograph.
The Great Orme Tramway is a cable-hauled 3 ft 6 in gauge tramway in Llandudno in north Wales. Open seasonally from late March to late October, it takes over 200,000 passengers each year from Llandudno Victoria Station to just below the summit of the Great Orme headland. From 1932 onwards it was known as the Great Orme Railway, reverting to its original name in 1977.
Tramway track is used on tramways or light rail operations. As with standard rail tracks, tram tracks have two parallel steel rails, the distance between the heads of the rails being the track gauge. When there is no need for pedestrians or road vehicles to traverse the track, conventional flat-bottom rail is used. However, when such traffic exists, such as in urban streets, grooved rails are used.
The Bordeaux tramway network consists of four lines serving the city of Bordeaux in Nouvelle-Aquitaine in southwestern France. The system has a route length of 77.5 kilometres (48.2 mi), serving a total of 133 tram stops.
The history of trams, streetcars, or trolleys began in the early nineteenth century. It can be divided up into several discrete periods defined by the principal means of motive power used.
The stud contact system is an obsolete ground-level power supply system for electric trams. The studs were cylinders with their tops flush with the road surface, and connected to an electrical cable underground. The studs contained a switch mechanism that made an electrical connection with the top of the stud when a car with a strong magnet at its underside passed over it, before automatically disconnencting. Electrical current was collected from the studs by a "skate" or "ski collector" under the tramcar.
A current collector is a device used in trolleybuses, trams, electric locomotives and EMUs to carry electric power (current) from overhead lines, electric third rails, or ground-level power supplies to the electrical equipment of the vehicles. Those for overhead wires are roof-mounted devices, those for rails are mounted on the bogies.
Trams in France date from 1837 when a 15 km steam tram line connected Montrond-les-Bains and Montbrison in the Loire. With the development of electric trams at the end of the 19th century, networks proliferated in French cities over a period of 15 years. Although nearly all of the country's tram systems were replaced by bus services in the 1930s or shortly after the Second World War, France is now in the forefront of the revival of tramways and light rail systems around the globe. Only tram lines in Lille and Saint-Étienne have operated continuously since the 19th century; the Marseille tramway system ran continuously until 2004 and only closed then for 3 years for extensive refurbishment into a modern tram network. Since the opening of the Nantes tramway in 1985, more than twenty towns and cities across France have built new tram lines. As of 2024, there are 28 operational tram networks in France, with 3 more planned. France is also home to Alstom, a leading tram manufacturer.
Road powered electric vehicles (RPEV) collect any form of potential energy from the road surface to supply electricity to locomotive motors and ancillary equipment within the vehicle.
Torquay Tramways operated electric street trams in Torquay, Devon, England, from 1907. They were initially powered by the unusual Dolter stud-contact electrification, but in 1911 was converted to more conventional overhead-line supply. The line was extended into neighbouring Paignton in 1911 but the whole network was closed in 1934.
Stalybridge, Hyde, Mossley & Dukinfield Tramways & Electricity Board (SHMD) was a public transport and electricity supply organisation formed by Act of the British Parliament in August 1901. It was a joint venture between the borough councils of Stalybridge, Hyde, Mossley and Dukinfield. The system was officially opened on 21 May 1904.
The Clermont-Ferrand tramway was a tram system in the French city of Clermont-Ferrand between 1890 and 1956. A new system came into operation in 2006.
Alstom APS, also known as Alimentation par Sol or Alimentation Par le Sol, is a form of ground-level power supply for street trams and, potentially, other vehicles. APS was developed by Innorail, a subsidiary of Spie Enertrans, but was sold to Alstom when Spie was acquired by Amec. It was originally created for the Bordeaux tramway, which began construction in 2000 and opened in 2003. From 2011, the technology has been used in a number of other cities around the world.
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