Twelfth progress report of the investigation of impact of h-ighway bridges / prepared as a part of an investigation con-ducted by the Engineering Experiment Station University of -Illinois ; in cooperation with the Division of Highways Sta-te of Illinois and U.S. Department of Commerce Bureau of Pu-blic Roads 

 - Urbana, Ill. : University of Illinois 
 - [94] p. 
 - Progress report ; no.12 .