This project developed driving simulator models and an experimental design to test signage placement impacts on driver capability to navigate three intersection types: Standard, Grade Separated Quadrant, and Grade Separated Contraflow. Driver performance was monitored using situational awareness and workload measures as well as operational measures such as speed deviation, lane changing, and deceleration.
Based on the research effort findings, it is recommended that signing engineers develop novel junction sign configurations, or provide additional guidance signs upstream of the decision point for intersections with non-traditional movements in order to offset low driver situational awareness and high cognitive workload, and to support timely lane changing behavior.
The quadrant grade separated intersection design appears to be a feasible alternative to standard intersections with or without lane assignment signs and when using side-mounted decision point signs and providing lane information on the junction sign.
Consequently, the results of this study provide some guidance for highway systems engineers on the need for novel signage designs to ensure effective driver information processing under unique highway configurations with performance comparable to standard intersections. From the data collected in this research, it is inferred that driver performance compared to standard intersections is similar at intersection forms with a non-intuitive turning movement (e.g. turn left to go right), whereas drivers at intersection forms which require advanced lane changing (e.g. contraflow and displaced left turns) may require additional guidance beyond that provided at standard intersections.
