Roughly 20 percent of MnDOT's inventory of anchor bolts for sign structures, light towers and traffic signals may be loose at any given time. Researchers examined specifications and procedures for tightening anchor bolts in Minnesota, and conducted lab and field tests on new approaches tailored to various bolt-and-nut configurations. New specifications and instructions will help crews lubricate and tighten bolts properly and ensure lasting safety of signs and lights in Minnesota's highway system. Numerical models will allow anchor configurations that may be adopted in the future.
