No person owning or operating any steam, electric, interurban, or street railroad, shall use any rails other than grooved girder rails not less than seven (7) inches in height, of such pattern and dimensions as shall be approved by the Board, in the track or in the construction of any new track of such stream, electric, interurban or street railroad, upon, along or across any street that shall, after the effective date of Ordinance No. 29,121, approved February 3, 1914, be paved or is paved with asphalt, vitrified brick, stone blocks or other permanent pavement, except on curves where guard rails are used, or on track crossings, or switches, or upon steel bridges, or on those portions of streets where the gradient exceeds ten per centum, or on any street intersection at the lower termination of gradients exceeding ten per centum.