tie(redirected from tie down)
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a support for rails in the form of a beam laid on top of the ballast layer of the roadbed. Ties ensure that the positions of the two rails do not change with respect to each other. They accept pressure from the rails and transmit it to the ballast layer. In the USSR ties are made of reinforced concrete (270 cm long) or wood (primarily softwoods) impregnated with antiseptics (275, 280, and 300 cm long); some foreign ties are made of metal. One kilometer of railroad track requires 1,600,1,840, or 2,000 ties.