Gantlet track
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A gantlet track (in British and Australian English: gauntlet track, gauntleted track or interlaced track; originally American, passing track) refers to the situation where tracks converge onto a single roadbed and are interlaced to pass through a narrow passage such as a cutting, bridge, or tunnel. A switch frog at each end allows the two tracks to overlap, and the four rails run parallel through the passage on the same crossties (sleepers) and separate again at the other end.
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[edit] Usage and origins
Gantlet tracks are commonly used when a rail line's capacity is increased with the addition of an additional track, but cost or other factors prevent the widening of the bridges. They are particularly used in funiculars where there is limited width for a complete four-rail system or a desire to hold down the costs of a full four-rail system, as seen in the photo to the right, Angels Flight, Los Angeles. Since there are no points or other moving parts in a gantlet track, a train operating on one of the tracks cannot be routed onto the other. Because two trains cannot use the gantlet at the same time, scheduling and block signals must allow for this restriction.
The term is derived not from gauntlet meaning a type of glove, but from the expression running the gauntlet, which means running between two confining rows of adversaries.
A gauntlet track can also be used to move a switch away from a heavily trafficked road, as used on the Mannheim tram system.
An alternative arrangement is to use three rails (dual gauge), with the two tracks sharing the middle rail. Gantlet track is typically used for short stretches of track where it is cheaper to provide extra rails than to provide switches and reduce the line to single track.
[edit] Passing track
The originator of the passing track was Prof. Thaddeus Lowe with his Mount Lowe Railway in Altadena, California (1893 - 1938). In an attempt to negotiate the steep climb of Mount Echo, Lowe was informed by his chief engineer David Macpherson that the grading required to accommodate the usual four rails would be extensive and costly. Most of the concern was caused by a large granite chasm that would require extensive backfilling and shoring. Overnight Lowe came up with a three-rail configuration that employed four rails only at the dead center or passing section of the funicular. This configuration became a world wide standard for funicular railways.
[edit] Examples worldwide
[edit] America
A gauntlet track can also be used when two railroads of different gauges share right-of-way; the standard-gauge Delaware, Lackawanna and Western Railroad used the wide-gauge Erie Railroad's tunnel through the New Jersey Palisades in this way before the DL&W built its own tunnel. The DL&W also used a guantlet track arrangement to allow two sets of track of the same gauge to pass through the Oxford Tunnel in Oxford, New Jersey. In this latter arrangement, the tracks overlapped within the tunnel, without the use of switches, so that the tracks travelled down the center of the tunnel where the overhead clearance was greater. The disadvantage of such an arrangement is that the tunnel has, in effect, only single-track capacity. On low-density traffic lines, such an arrangement would probably not be problematic, although higher density use could cause delays.
[edit] Australia
The Como River bridge was built as single line in the 1880's. The line was duplicated soon after, except for the bridge. The bridge was fitted with a gantlet track, which needs no turnouts, and hence needs no signal box at the far end. The bridge was replaced with a double track bridge around 1973.
Another example is visible in the tunnel under George Street, Railway Square, at part of the spur which leads from the connection between Sydney's intercity terminus and Redfern. This particular example was formerly a 4-track tunnel but became a gantlet track when the structure gauge was increased to accommodate CityRail's double-decker carriages. A single track continues on to the PowerHouse Museum and can be visited as part of the Ultimo Pedestrian Network. This track formerly served the Darling Harbour goods yards and was disconnected from rest of the corridor when it formed part of the Sydney Light Rail network.
[edit] Canada
A four rail gantlet track still exists on the Canadian Pacific Railway Bridge across the Rivière des Prairies between Montréal and Laval because the structure gauge is not sufficiently wide for a regular double track. This bridge is used by freight trains of the Canadian Pacific Railway (CPR), the Chemins de Fer Québec-Gatineau (CFQG) (or the Quebec Gatineau Railway (QGR)) and by the Blainville Line suburban trains of the Agence métropolitaine de transport (Metropolitan Transportation Agency)
[edit] Germany
In Mannheim, a gauntlet track is used to shift the switch out of the road to prevent the switch from being driven over by cars and trucks. Mannheim also uses a gauntlet track to run trams within less space.
[edit] The Netherlands
Because of space constraints, Amsterdam's tram network uses gauntlet track for three main routes into the city centre.
[edit] United Kingdom
In Britain gauntleted track is frequently called interlaced track and was often used where street tramways had to pass through narrow streets and even archways in ancient city walls. Two modern examples of short sections of interlaced track are to be found on the Tramlink system in South London. One of these examples is a conventional use where a short obstruction prevents two tracks being laid side by side. The other is rather more unusual as it is not strictly necessary but done to avoid a set of points being located in the middle of a traffic junction as this would cause maintenance problems.
[edit] See also
- A section of gauntlet track on Croydon Tramlink
- Rail terminology (US/UK differences highlighted)
[edit] External links
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- Gauntlet track - four rails in Minneapolis (with diagram)
