, Professor, Mechanical Engineering
The Cooperative Intersection Collision Avoidance-Stop Sign Assist (CICAS-SSA) system is an infrastructure-based driver-support system intended to improve gap decision making at rural median-separated stop-controlled intersections. The CICAS-SSA system tracks vehicle locations on a major roadway and then displays a message to a driver on a minor road via a changeable message sign. The three studies included in this project examined the transition from an infrastructure-based rural intersection crossing-assist system to one located inside a vehicle. The primary goals of the first study, conducted in a simulator, were to examine the effect of potentially confounding factors, such as the drivers' familiarity with the assist system and the impact of cognitive load on the drivers' performance. Next, the research examined the efficacy of several different designs of such a system to determine the optimal interface design to use for the in-vehicle system. Finally, the optimal design of the system was examined in the third study, as a field test. Results showed that the use of the system under cognitively demanding conditions did not result in any adverse consequences, which suggested that the processing of the system required minimal cognitive resources. Additionally, the results showed that the benefits of the assist system, such as reduced probability of accepting a critical gap, were exhibited under the limited visibility conditions when the perceptual task of determining an appropriate crossing gap became overly demanding. The results from the field study showed that the use of the assist system resulted in improved intersection crossing performance, exhibited in an increased likelihood of making a complete stop at the stop sign, and showed a strong trend toward a decreased probability of accepting critical gaps. Additionally, the impact of the in-vehicle CICAS-SSA was equivalent for older and younger drivers--that is, both age groups benefited from use of the system.