The purpose of this study was to develop recommendations for signing, delineation, and geometric design that will reduce workloads at critical points approaching interchanges that exhibit a high degree of complexity. In the development of these recommendations, the following activities were completed: identification of attributes influencing interchange complexity; evaluation of current geometric design, signing, and marking practices; a simulator study investigating driver behavior at different interchange layouts; and a field study investigating real-world driver behavior at complex interchanges.
This report details the process and outcomes of these activities to develop key findings with regard to traffic control devices, pavement markings, and geometric design being implemented across the country. Six categories of recommendations (treatments) were identified and discussed. Each treatment is the result of understanding the interrelationships of various attributes within each research topic and the application of those relationships to practice outcomes. The report describes each treatment with examples of undesirable practices as well as anticipated and observed outcomes, provides existing design guidelines with a general perspective on implementations in multiple jurisdictions, outlines the primary principles of the concept, provides application examples, provides specific recommendations to address undesirable practices, and summarizes the breadth and depth of implementation options. This project was conducted under the Traffic Control Device Consortium Pooled Fund Study.
The key project objective is to identify potential improvements to current marking and signing practices for complex interchanges. A human factors study will be conducted to examine these alternative signing and marking treatments to determine their effects on driver decisionmaking, comfort, and safety.