Driver Acceptance and Use of a Speed Limit and Curve Advisor 2011-01-0550

This research examined driver acceptance and behavior associated with Speed Limit and Curve Advisor systems, including influences on speed choice. Drivers experienced messages from an emulated Speed Limit and Curve Advisor system during a 2-hour public road drive. Driver tolerance for system errors and message conflicts was also studied by manipulating the accuracy of the information provided by the system. Messages were presented using either a Head-Up Display or on an in-dash Driver Information Center. Results indicate that drivers liked having speed limit information continuously available to them while driving, but the information provided by the Speed Limit Advisor did not significantly influence or alter drivers' speed choice or deceleration profiles in comparison to driving without the system. The vast majority of drivers reported that they relied on both in-vehicle and external sources of information, and incorrect information provided by the system (e.g., speed limit presented was higher than the posted speed limit) or missing speed limits (i.e., no externally posted speed limit information) did not appear to significantly influence drivers' speed choice. This was the case at transition points surrounding speed limit changes, as well as during extended periods of driving with no externally posted speed limit signs where drivers may have desired to confirm the legal speed limit. Unreliability in the system (represented by inaccurate or missing information) was found to lead to decreased trust in the system, but did not significantly change drivers' basic perception of the utility of the concept. Driving profiles related to approaching and negotiating curves were also not influenced by the presence or absence of Curve Advisor messages.