All trains or engines run upon a railroad in this State which intersects or crosses or is intersected or crossed by another railroad upon the same level, shall be brought to a full stop and the whistle sounded at a distance of not less than 100 feet nor more than 1,000 feet from the point of intersection or crossing, before such intersection or crossing is passed by such train or engine. The full stop and crossing on signal, with the approval of the Transportation Board, may be discontinued if an interlocking switch and signal apparatus is adopted, installed, and put in operation by such railroads at such crossing or intersection of two railroads. (Amended 1959, No. 329 (Adj. Sess.), § 39(b), eff. March 1, 1961; 1993, No. 172 (Adj. Sess.), § 58.)