Drivers' understanding of overhead freeway exit guide signs: Evaluation of alternatives with an advanced fixed-base driving simulator

In the near future, Route 1A southbound as it passes around Logan International Airport in Boston, Massachusetts, will be rebuilt. The existing four-lane highway will split into three different roadways: two one-lane exits and one two-lane throughway. Drivers will have very little time to decide which lane or lanes to take for a given destination. Given the complex geometry and small warning time, there is some concern that drivers will either miss the Logan exit altogether (leading to a long and frustrating detour around Logan) or make a decision at the last moment to move into the exit lane (leading to a potential safety problem). Proposed and alternative ways of signing exits such as this one with complex multiple splits were evaluated on an advanced fixed-base driving simulator. The virtual roadways and signs were built using the actual engineering design drawings. Drivers sit in a real Saturn and operate the controls of this vehicle just as they would those of a normal vehicle. They are given Logan as their target destination. The alternative freeway guide signs were found to improve indices of driver safety and satisfaction. Specifically, drivers using the alternative signs move into the exiting lane sooner, make fewer double lane changes, and miss their exit less often. The results have implications more generally for the design and testing of highway guide signs using a driving simulator.