(a) Within the corporate limits of cities, a railroad company shall not be required either to erect the blowpost provided for in Code Section 46-8-190 or to blow the whistle of its locomotives in approaching a crossing in said corporate limits. However, in lieu thereof, the engineer of each locomotive shall be required to signal the approach of his train to such crossing in said corporate limits by constantly tolling the bell of the locomotive; and on failure to do so, the engineer shall be guilty of a misdemeanor.

(b) Nothing in this Code section shall be held to relieve the engineer or the railroad company of his or its duty of keeping and maintaining a constant and vigilant lookout along the track ahead of the engine while moving within the corporate limits of a city. In addition, nothing in this Code section shall be held to excuse such railroad company or such engineer from exercising due care in so controlling the movements of such trains as to avoid doing injury to persons or property which may be on such crossing within said city or within 50 feet of the crossing on the line of such railway, or from observing any ordinance of such city regulating the speed at which railroad trains may be run therein.