Can signing guide design? This paper documents a process that considers signing issues throughout the project development stages of freeway system interchanges. In particular, a detailed system interchange configuration study process is discussed, providing guidance in evaluating guide signing issues and related factors (i.e. route continuity, design uniformity, driver expectancy) in coordination with traffic operations, roadway geometrics, and safety to determine optimal interchange configurations. The Configuration Study of the Northeast Interchange of Interstates 35, 80, and 235 in Des Moines, Iowa is used as a case study to demonstrate this process. The study was performed for the Iowa Department of Transportation (IaDOT) and included the development and refinement of alternative system interchange configurations to determine a preferred configuration. Signing needs played a key role in the alternative development process due to the tight spacing of adjacent service interchanges and the complexity of signing the eastbound to northbound I-35 movement through the system interchange. The case study was an enlightening project amplifying the importance given to guide signing issues early in the project development process. This study demonstrated that guide signing needs may significantly influence the selection of optimal system interchange configurations.
Abstract