Driver Expectations When Navigating Complex Interchanges

completed

The purpose of this project was to develop a method for determining driver expectations at interchanges and to use that method to determine how these expectations affect driver behavior at interchanges that vary in level of complexity, including provision of initial recommendations for navigation signage to aid complex interchange design. Interchange navigation presents a range of challenges that are different from those associated with driving on continuous roads, and driver errors at interchanges are often more difficult to correct since drivers transfer to a grade-separated freeway, highway, or roadway, which provides limited access points for their return to the original roadway. Clear navigation signage is needed to guide drivers and minimize errors. Although there has been previous research performed on signage in general, research specifically on driver expectations and interchange signage has been limited. Moreover, there is little consensus on a single best way to design signs for interchanges, and available data present an incomplete picture of guidance relevant to sign design. This project involved multiple tasks to study driver expectations, including: A literature review of prior work on driver navigation problems and driver expectations at interchanges. A series of focus groups to collect qualitative information about driver expectations. A task analysis of different interchange navigation scenarios. A experimental study to collect data on driver performance given various complex interchange signage alternatives. This project yielded several overall conclusions related to driver expectations at interchanges. The focus groups indicated that most drivers have problems at complex, unfamiliar interchanges, and they become stressed when they do not receive the information they expect, if they are surprised, or required to execute multiple lane changes in a short distance. The task analysis indicated that multiple concurrent driving tasks may be common in complex interchanges, and could lead to higher workload. Finally, the empirical data collection activities showed, among other findings, that perceptual factors associated with the spatial layout of signs have a significant impact on driver interpretation of guidance information. The problems that drivers experience and their responses to those challenges potentially have implications for safety and capacity at complex interchanges. This project was conducted under the Traffic Control Device Consortium Pooled Fund Study.