Section 31-5-305 - Special speed limit at bridges and other elevated structures(a) No person shall drive a vehicle over any bridge or other elevated structure constituting a part of a highway at a speed which is greater than the maximum speed which can be maintained with safety to the bridge or structure when the structure is signposted as provided in this section. (b) The superintendent and local authorities on highways under their respective jurisdictions may conduct an investigation of any bridge or other elevated structure constituting a part of a highway, and if he or they find that the structure cannot with safety to itself withstand vehicles traveling at the speed otherwise permissible under this act, the superintendent or local authorities shall determine and declare the maximum speed of vehicles which the structure can safely withstand and shall cause or permit suitable signs stating the maximum speed to be erected and maintained before each end of the structure. (c) Upon the trial of any person charged with a violation of this section, proof of the determination of the maximum speed by the superintendent and the existence of the signs constitutes conclusive evidence of the maximum speed which can be maintained with safety to the bridge or structure.