(rail transport) rails laid parallel to a running rail to guide wheels through points, rail crossings, and round curves, to reduce wear and the risk of derailments such as those due to flange climb.
1869, Colonel W. Yolland, Accounts and Papers volume 21 Railways; Turnpikes; Highways; Harbours, &c., Session 10 December 1868 — 11 August 1869, Volume LIV., House of Commons, Railways, page 42:
I think it of great importance that the whole of this portion of the Brecon and Mertyr Railway, which originally was an old mineral line (the old Rumney), should be carefully examined by the Company's engineer, to ascertain if there are any other curves of 10 or 12 chains radius or less on the running lines, and that such curves should be rendered more safe, by the addition of check rails round such curves.
2000, J. S. Mundrey, “Railway Curves”, in Railway Track Engineering, Third Edition edition, Tata McGraw-Hill, ↑ISBN, Movement of Vehicles on Curves, page 199:
The pressure of the flange of the leading wheel against the outer rail leads not only to excessive wear but also to risk of tyre climbing up over the rail. To minimise this risk, a check rail is fixed inside the inner rail and made parallel to it.
2008, John Wolfe Wolfe Barry, “Permanent Way”, in Railway Appliances, BiblioBazaar, ↑ISBN, Superelevation, page 58/60:
The extra rail, which is called a check rail, relieves the sideways pressure of the wheels against the out rail, and prevents the wheels from mounting the outer rail