Section 625 ILCS 5/11-608 - Special speed limitation on 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 such bridge or structure, when such structure is sign posted as provided in this Section.(b) The Department upon request from any local authority shall, or upon its own initiative may, conduct an investigation of any bridge or other elevated structure constituting a part of a highway, and if it shall thereupon find that such structure cannot with safety to itself withstand vehicles traveling at the speed otherwise permissible under this Chapter, the Department shall determine and declare the maximum speed of vehicles which such structure can safely withstand, and shall cause or permit suitable signs stating such maximum speed to be erected and maintained before each end of such 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 Department and the existence of such signs is conclusive evidence of the maximum speed which can be maintained with safety to such bridge or structure.