Passing loop

A passing loop (UK usage) or passing siding (North America) (also called a crossing loop, crossing place, refuge loop or, colloquially, a hole) is a place on a single line railway or tramway, often located at or near a station, where trains or trams travelling in opposite directions can pass each other. Trains/trams going in the same direction can also overtake, provided that the signalling arrangement allows it. A passing loop is double-ended and connected to the main track at both ends, though a dead end siding known as a refuge siding, which is much less convenient, can be used. A similar arrangement is used on the gauntlet track of cable railways and funiculars, and in passing places on single-track roads. Ideally, the loop should be longer than all trains needing to cross at that point. Unless the loop is of sufficient length to be dynamic, the first train to arrive must stop or move very slowly, while the second to arrive may pass at speed. If one train is too long for the loop it must wait for the opposing train to enter the loop before proceeding, taking a few minutes. Ideally, the shorter train should arrive first and leave second. If both trains are too long for the loop, time-consuming "see-sawing" (or "double saw-by") operations are required for the trains to cross (see Tawa railway station).…

A passing loop (UK usage) or passing siding (North America) (also called a crossing loop, crossing place, refuge loop or, colloquially, a hole) is a place on a single line railway or tramway, often located at or near a station, where trains or trams travelling in opposite directions can pass each other. Trains/trams going in the same direction can also overtake, provided that the signalling arrangement allows it. A passing loop is double-ended and connected to the main track at both ends, though a dead end siding known as a refuge siding, which is much less convenient, can be used. A similar arrangement is used on the gauntlet track of cable railways and funiculars, and in passing places on single-track roads. Ideally, the loop should be longer than all trains needing to cross at that point. Unless the loop is of sufficient length to be dynamic, the first train to arrive must stop or move very slowly, while the second to arrive may pass at speed. If one train is too long for the loop it must wait for the opposing train to enter the loop before proceeding, taking a few minutes. Ideally, the shorter train should arrive first and leave second. If both trains are too long for the loop, time-consuming "see-sawing" (or "double saw-by") operations are required for the trains to cross (see Tawa railway station). On railway systems that use platforms, especially high-level platforms, for passengers to board and disembark from trains, the platforms may be provided on both the main and loop tracks or possibly on only one of them. This type of passing loop is common in Russia and post-Soviet states. A disadvantage of the platform and through arrangement is the speed limits through the turnouts at each end. Refuge sidings are used at locations with gradients too steep for heavy freight trains or steam haulage to depart from conventional passing loops, or confined spaces where a passing loop cannot be built. An extra parallel siding is often built at stations on refuge sidings so that two stopping trains can pass, and an extended catch point opposite the refuge siding may be added so as not to interfere with passing trains. Overtaking loops can also be provided on dual track lines, typically at stations, for the purpose of providing a location for express trains to overtake local trains. This layout has extensive use in high-speed rail and East Asian rapid transit systems. In this layout a local train enters the siding allowing a scheduled express train to overtake it. File:Station Track layout-2.svg|Double platform road and through road: Passing loop configuration allowing local trains to serve the station and wait for an express service to pass straight through the station to overtake uninterrupted. File:Station Track layout-1.svg|Double main and loop: Passing loop configuration allowing express and local trains to serve the station before the express service overtakes the local service. ==Gallery== File:Penryn trains passing 2 (cropped).jpg|Trains in a passing loop at Penryn railway station in the United Kingdom File:TwoTrainsAtPassingSidingInBoltonOntario.jpg|Passing sidings in North America can be very long. This one in Bolton, Ontario – the track on the right – measures some . File:Funicular to Horseshoe Curve viewing area (8999490400).jpg|A short passing track on a funicular in Pennsylvania

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