Iowa Code Title VIII. Transportation [Chs. 306-330B] § 321.295. Limitation on bridge or elevated structures

1. A person shall not drive a vehicle on any public bridge or elevated structure at a speed which is greater than the maximum speed permitted under this chapter on the street or highway at a point where said street or highway joins said bridge or elevated structure. However, if the maximum speed permitted on said street or highway differs from the maximum speed on any other street or highway joining said bridge or elevated structure, then the lowest of those maximum speeds shall be the maximum speed limit on said bridge or elevated structure unless the department, upon request from any local authority or upon its own initiative, has conducted an investigation of the bridge or other elevated structure constituting a part of the highway, and has found that the structure cannot with safety to itself withstand vehicles traveling at the speed otherwise permissible under this chapter. Under those circumstances, the department shall determine and declare the maximum speed of vehicles which the structure can withstand, and shall cause or permit suitable signs stating such maximum speed to be erected and maintained at a distance of two hundred feet before each end of such structure.

2. A person shall not 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 such bridge or structure, when the structure is signposted as provided in this section.

3. Upon the trial of any person charged with driving a vehicle at a speed which is greater than the maximum speed which can be maintained with safety to such bridge or structure, proof of such determination of the maximum speed by said department and the existence of said signs shall constitute conclusive evidence of the maximum speed which can be maintained with safety to such bridge or structure.