Henry Liu, Associate Professor, Civil Engineering
This research provides performance data and guidance on effective strategies for handling oversaturated conditions. As traffic congestion continues to grow significantly in the United States and throughout the world, agencies tasked with managing traffic control systems are more and more frequently challenged with moving traffic in congested conditions and situations where the traffic demand exceeds the capacity of the system. Under this condition of oversaturation, typical traffic control strategies do not work efficiently, particularly since the objectives of traffic control are decidedly different when mobility is restricted. As indicated by the results of the 2005 and 2007 Traffic Signal Operation Self Assessment surveys, the majority of agencies involved in the operation and maintenance of traffic signal systems are already stretched thin and challenged to provide adequate service to drivers in their jurisdictions. Oversaturated conditions present an additional burden for practitioners that do not have adequate tools for addressing such situations. This research is a component of NCHRP 03-90: Operation of Traffic Signal Systems in Oversaturated Conditions, funded by the National Cooperative Highway Research Program and involving researchers at the University of Minnesota, Virginia Tech, and the University of California Berkeley.