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Adhesion railway or adhesion traction is the most common type of railway, where power is applied by driving some or all of the wheels of the locomotive. Rail adhesion relies on the friction between a steel wheel and a steel rail. The term is particularly used when discussing conventional railways to distinguish from other forms of traction such as funicular or cog railway. Traction or friction can be reduced when the rails are greasy, because of rain, oil or decomposing leaves which compact into a hard slippery lignin coating. Measures against reduced adhesion due to leaves include application of "Sandite" (a gel-sand mix) by special sanding trains, scrubbers and water jets, and long-term management of railside vegetation. On an adhesion railway, most locomotives will have a sand containment vessel. Properly dried sand can be dropped onto the rail to improve traction under slippery conditions. The sand is most often applied using compressed air. When an engine slips, particularly when starting a heavy train, sand applied at the front of the driving wheels greatly aids in tractive effort causing the train to "lift", or to commence the motion intended by the engine driver. == Effect of adhesion limits == Adhesion is caused by friction, with maximum tangential force produced by a driving wheel before slipping given by: :Fmax= coefficient of friction × Weight on wheel Usually the force needed to start sliding is greater than that needed to continue sliding. The former is concerned with static friction, referred colloquially to as "stiction", or "limiting friction", whilst the latter is called "sliding friction". For steel on steel, the coefficient of friction can be as high as 0.78, under laboratory conditions, but typically on railways it is between 0.35 and 0.5,〔http://documents.epfl.ch/users/a/al/allenbac/www/documents/ResuTE31.pdf〕 whilst under extreme conditions it can fall to as low as 0.05. Thus a 100-tonne locomotive could have a tractive effort of 350 kilonewtons, under the ideal conditions (assuming sufficient force can be produced by the engine), falling to a 50 kilonewtons under the worst conditions. 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「Adhesion railway」の詳細全文を読む スポンサード リンク
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