Driver Workload Management during Cell Phone Conversations.

This study tested if intelligently suspending cell phone conversations during demanding driving situations would improve driver's performance and lessen subjective workload. Using a simulator, drivers followed a lead car approximately 2 seconds ahead and braking randomly. The drivers engaged inspontaneous "Neutral," "Intense," or "No" cell phone conversations with the experimenter, who sustained all conversations with scripted non-directive utterances. When the lead car started to decelerate, the conversations were suspended or not for the duration of the event. Objective driving performance and subjective "workload" estimates showed significant differences between conversation topic types. Engaging in an "Intense" conversation during deceleration produced (1) smaller decreases in forward velocity, and (2) delays in releasing the accelerator, applying the brake and decelerating. Suspending "Intense" conversations counteracted these effects, producing larger decreases in forward velocity, and speeding up drivers' responses on the vehicle controls. Furthermore, suspending conversations clearlyincreased drivers' headways and temporal distances with the lead car. Theresults show that cell phone conversation intensity has significant effects on both performance and workload. The results also show positive effects of suspending cell phone conversations during critical driving situations on driver performance, thus perhaps counteracting the negative effects of the workload imposed by the conversations. Subjective ratings and value judgments for this system indicate generally positive assessments of the system.