This study examined driver behavior when using an advanced in-vehicle traveler information system designed to provide drivers with auditory warnings of slow moving traffic ahead on busy freeways in the San Francisco Bay Area. Field testing was conducted with 24 volunteer drivers who drove four vehicles equipped with a prototype system designed to receive real-time traffic information from external sources, assess vehicle speed differentials and position relative to approaching traffic queues, and provide drivers with auditory alerts such as "Slow Traffic Ahead" to prevent drivers from being surprised and causing hard braking events.
Research conducted prior to testing indicated that drivers who have 60-90 seconds of warning prior to negotiating traffic queues execute fewer numbers of hard braking events. In this investigation, researchers wanted to evaluate associated safety benefits; however, since crash events were relatively rare in these cases, and difficult to track without high market penetration and extended study periods, researchers decided to use driving behavior as surrogate measure to evaluate safety before and after the system was activated for each driver in each vehicle.
During this experiment four vehicles were equipped. Each vehicle was outfitted with a data acquisition system (DAS) to record both engineering and video data to characterize vehicle motions, driver behaviors, and the operation of the in-vehicle Networked Traveler Foresighted Driving alert system installed. Vehicle and driver data were collected seven days prior to system activation in each vehicle and seven days after activation. Project testing lasted a total of 17 weeks. In addition to analyzing vehicle and driver observations, participants were asked to fill out a short, web-based survey for each audible driving alert they received. As an incentive for participation, participants were paid $100 and reimbursed for fuel costs during the study period.
A total of 766 trips were recorded prior to activation (audible muted) and 782 trips were recorded after activation. 718 audible alerts were issued to drivers on more than 293 trips when the system was activated. A trip was defined as the time from when the vehicle ignition was turned on until the time when the vehicle ignition was turned off.
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