General Tramways Act 1884

Every tramway line shall be constructed and maintained with two rails (the running surfaces of which shall be laid at a distance of four feet eight and a half inches from each other), and shall be constructed and maintained in such a manner that the uppermost surface of every rail shall be on a level with the surface of the road; and the rails used in the construction of every tramway shall be of iron or steel, and of the weight of not less than twenty pounds to the yard. And such rails shall be grooved, the groove in no case exceeding one and a quarter inches in width.