A grand union is a rail track junction where two double-track railway lines cross at grade, often in a street intersection or crossroads. A total of sixteen railroad switches (sets of points) allow a streetcar coming from any direction to take any of the three other directions.
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Complexity
These types of complex junction are expensive to build and expensive to maintain. Special parts, sometimes made of manganese steel, are needed for each location where one rail crossed another (a "frog"); these parts often need to be custom-made and fitted for each single location, depending on the specific angle of crossing of the intersecting streets.
A full grand union junction consists of 88 frogs (where one rail crosses another rail), and 32 switchpoints (point blades) if single-point switches are not used. A tram or train crossing the junction will encounter between four and twenty frogs within the space of crossing the junction.
For all of the possible tracks of a grand union to be used during normal operation, at least six different tram routes have to cross the union. In an intersection with lines oriented towards cardinal directions, these could be: north-south, north-east, north-west, south-east, south-west, and east-west.
Three-Quarter, Half, and Butterfly Unions
Three-quarter unions are similar to grand unions in that they are also rail track junctions where two double-track railway lines cross at grade, often in a street intersection or crossroads; the primary difference being that one corner of the crossing does not have curved junction tracks, with the union having a total of twelve railroad switches (sets of points).
Half unions are similar, but only have curved junction tracks on two adjoining corners of the intersection, with a total of eight switches/points.
Butterfly unions share the total of eight switches/points, but the curved junction tracks are on opposing corners.
Examples
- Melbourne, Australia: The only surviving grand union in the Southern Hemisphere is Balaclava Junction on the Melbourne tram system, in Australia.[1]
- Auckland, New Zealand: The Auckland system formerly had two grand unions, located at Queen Street's intersections with both Customs Street and Wellesley Street.[2]
- Toronto, Canada: The most extensive street railway system in North America is the Toronto streetcar system of the Toronto Transit Commission in southern Ontario, which has three grand unions.[3]
- Montreal, Canada: The system operated by Montreal Tramways Company (Montreal street railway system) had several[citation needed] grand unions, with one known to be at the intersection of Ste. Catherine and St. Lawrence Streets.[4].
- Edmonton, Canada: The Edmonton Radial Railway had a single grand union at the intersection of 109th Street and Jasper Avenue, although one side of the junction remained as a stub and was removed by the late 1930s.[5][6]
- Rochester, New York State, USA: Rochester's surface streetcar system had three full grand unions, all of which were located on Main Street, as well as two three-quarter unions, and three half unions.[7][8]
- Philadelphia, Pennsylvania, USA: SEPTA has a surviving example of a half union located at the intersection of Chester Avenue and 49th Street;[9][10] and PTC previously had two butterfly unions, the first at Erie Ave and Old York Road[11] and the second at Lancaster Avenue and 33rd Street.[12]
- Chicago, Illinois, USA: The Chicago Transit Authority has a three-quarter union at Tower 18, located on the northwest corner of The Loop (CTA).[13]
- Amsterdam, Netherlands: As of 2009[update], the Amsterdam tram system continues to have four grand unions. However, none of them has tram routes running in all directions under normal operation.[14]
- United Kingdom: The UK had at least four grand unions, at Salford, South Shields, Liverpool, and Walthamstow. The components of the Salford union are presently stored at the National Tramway Museum at Crich.[citation needed]
References
- ^ Victorian Heritage Database: photographs and diagram of junction
- ^ Graham Stewart, The End of the Penny Section: When Trams Ruled the Streets of New Zealand, rev ed. (Wellington: Grantham House, 1993), p. 149.
- ^ http://transit.toronto.on.ca/archives/maps/cars06.pdf
- ^ Musée McCord Museum photograph - Tramway crossing under construction, 1893
- ^ Edmonton Radial Railway 1924 track map
- ^ Edmonton Radial Railway Society photograph, 109th St. and Jasper Ave., 1904
- ^ Map of Rochester Subway, see inset section for surface track layout
- ^ Powers Building photograph, Rochester NY, 1904
- ^ Original PRT specialwork drawing sheet 10, chart 48.
- ^ PTC Track Map detail, 1954, bottom right corner of image
- ^ Original PRT specialwork drawing sheet 16, chart 66.
- ^ PTC Track Map detail, 1954, center left of image
- ^ www.Chicago-L.org Photo "tower18l.jpg" taken June 19, 2006.(Retrieved November 2009)
- ^ see Sporenplan.nl
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