Concrete Median Barrier (CMB) is a guardrail system that, when placed along a roadway, is intended to contain and redirect a vehicle that has left the travel lane. In doing so, CMB can reduce the severity of an accident by preventing a vehicle from crossing over into oncoming traffic or striking a more substantial fixed object. Since the 1990’s, the Montana Department of Transportation (MDT) has been using CMB in certain areas, such as between opposing lanes of traffic on some interstate segments. The CMB sections that are used are shaped barriers approximately 10 feet long and joined together by pin and loop connections using two wire rope loops cast in each end of each barrier.

Based on current NCHRP procedures, as well as concerns about corrosion, MDT has begun to replace two loop CMB connection systems with three loop systems on a project-by-project basis. As part of this process, MDT is interested in determining what information is available on CMB in general, the maintenance of barrier connection systems, understanding the corrosion mechanisms at work and approaches to address them on existing and future installations, and what approaches may be taken in developing and implementing a transition plan for replacing CMB.

Through this project, the research team prepared a synthesis of available information regarding concrete median barriers, with a specific focus on the corrosion of link-pin systems, general literature and reports on CMB, corrosion of connection systems and approaches to rating/ranking that corrosion, any current state DOT practices regarding CMB maintenance and replacement programs, and potential transition plans for the replacement of barriers. The synthesis document will aid MDT in characterizing and addressing CMB corrosion in current and future CMB deployments, and in developing a transition plan to implement identified solutions.