Evaluating Design Options for a Dynamic Traffic Sign

This study describes two usability methods that were used to determine the final design of a prototype dynamic traffic sign. The Cooperative Intersection Collision Avoidance System-Stop Sign Assist (CICAS-SSA) is an infrastructure-based driver support system to improve gap acceptance at rural stop-controlled intersections. This study evaluated drivers’ comprehension of recommended design changes made to the SSA message set using paper-and- pencil and computerized testing. The goal was to choose the final interface design that would later be tested using driving simulation. Overall, comprehension was highest for sign messages that showed prohibitive information and was lowest for signs indicating no traffic was detected near the intersection. The results for the design options were similar between studies, allowing for the selection of a final set of design features for the interface. Results also suggest that the two methodologies provided a low-cost alternative to simulation for down-selecting the design options.