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The cant of a railway track (also referred to as superelevation) or a road (sometimes referred to as cross slope or camber) is the difference in elevation (height) between the two edges. This is normally done where the railway or road is curved; raising the outer rail or the outer edge of the road providing a banked turn, thus allowing vehicles to maneuver through the curve at higher speeds than would otherwise be possible if the surface was flat or level. == Rail == On railways, cant helps a train steer around a curve, keeping the wheel flanges from touching the rails, minimising friction and wear. The main functions of cant are to: * Better distribute load across both rails * Reduce rail- and wheel-wear * Neutralise the effect of lateral forces * Improve passenger comfort The necessary cant in a curve depends on the expected speed of the trains and the radius. However, it may be necessary to select a compromise value at design time, for example if slow-moving trains may occasionally use tracks intended for high-speed trains. Generally the aim is for trains to run without flange contact, which also depends on the tyre profile of the wheels. Allowance has to be made for the different speeds of trains. Slower trains will tend to make flange contact with the inner rail on curves, while faster trains will tend to ride outwards and make contact with the outer rail. Either contact causes wear and tear and may lead to derailment. Many high-speed lines do not permit slower freight trains, particularly with heavier axle loads. In some cases, the impact is reduced by the use of flange lubrication. Ideally, the track should have sleepers (railroad ties) at a closer spacing and a greater depth of ballast to accommodate the increased forces exerted in the curve. At the ends of a curve, the amount of cant cannot change from zero to its maximum immediately. It must change (ramp) gradually in a track transition curve. The length of the transition depends on the maximum allowable speed—the higher the speed, the greater length is required. For the United States standard maximum unbalanced superelevation of , the formula is: : The maximum value of cant (the height of the outer rail above the inner rail) for a standard gauge railway is about . For high-speed railways in Europe, maximum cant is (when slow freight trains are not allowed).〔2002/732/EC. *, Commission Decision of 30 May 2002 concerning the Technical Specification for Interoperability〕 Track unbalanced superelevation (cant deficiency) in the United States is restricted to , though is permissible by waiver. The maximum value for European railways varies by country, some of which have curves with over of unbalanced superelevation to permit high-speed transportation. The highest values are only for tilting trains, because it would be too uncomfortable for passengers. 抄文引用元・出典: フリー百科事典『 ウィキペディア（Wikipedia）』 ■ウィキペディアで「Cant (road/rail)」の詳細全文を読む スポンサード リンク
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