The purpose of this project was to identify design constraints related to signing, markings, and geometry for complex interchanges, and then to identify useful topics for future research that will yield findings that can address those design issues. Obtaining this feedback was an important way to ensure that future research remains calibrated with the information needs of engineers and other practitioners. This project involved conducting phone interviews with 17 State transportation departments, represented by 28 individuals. These interviews provided information about how stakeholders identify problem interchanges, what types of problems occur, how they can address those problems, and how they deal with unique configurations that are not covered by existing design references. Complex interchanges pose an ongoing challenge to roadway engineers and State transportation department personnel. These interchanges often involve multiple routes that converge or diverge within a short distance, resulting in geometric or signing elements that ultimately cause higher workload for drivers. However, there is no simple definition or single prototype example of a “complex interchange”, and a variety of geometric and signing elements can make different interchanges complex and difficult for drivers to navigate. Consequently, the human factors problems that drivers can face at these interchanges also vary greatly, which is reflected in the wide range of research needs identified by stakeholders. They also see value in additional research and design guidance that would address these information gaps. (Author/publisher)
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