The speed of vehicular traffic over any portion of any street, avenue, road, highway or other thoroughfare within the city used by vehicular traffic, which area is under construction or repair and properly marked by signs as such, shall not exceed twenty (20) miles per hour, and the speed limits hereinabove established shall be altered accordingly when such construction conditions exist, except in any area where a lower speed limit has been established and in such event the lower speed limit shall govern.
(Code 1958, § 29-2)