It is hereby declared to be unlawful to operate over or upon any of the public streets of the city any detachable trailer unless the same shall be firmly connected to the towing vehicle by some mechanically sound device to prevent any detachment therefrom when in motion, together with an auxiliary or independent device such as a chain or cable, which would, in the event of a disruption of the principal towing device, prevent the trailer from being detached from the towing vehicle.
(Code 1958, § 30-7)