Abstract
This paper presents the final results of a connected-vehicles field experiment conducted under the U.S. Department of Transportation's SafeTrip-21 Initiative. A real-time freeway end-of-queue alerting system was developed and tested at 3,400 locations along San Francisco Bay Area freeways in California. The Networked Traveler Foresighted Driving Advanced Driver Assistance System, which used vehicle-to-infrastructure communication, provided drivers with an auditory alert when they approached slow traffic ahead on a freeway to improve the driver's situational awareness. The system was not a last-second collision warning; rather, it was designed to provide soft safety alerts approximately 60 s before the driver reached the slowed traffic. Twenty-four drivers participated in the experiment, and each was given an instrumented vehicle for 2 weeks. During the first week, the alerting system was active but muted, providing a measure of baseline driving behavior. During the second week, auditory alerts sounded whenever the driver approached traffic moving at least 15 mph slower. The desired outcome was an increase in driver situational awareness resulting in a smoother transition into the end of the queue and a reduction in the risk of rear-end crashes. Drivers rated the majority of alerts as either good or neutral and found the system most useful when they encountered an unexpected traffic queue. Several driving performance metrics were also examined. In addition to a smoother deceleration profile, the auditory alerts provided a small but significant reduction in mean peak deceleration rates during morning and off-peak travel as compared with baseline conditions.
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