Annoyance may merit as much attention as urgency in the design of auditory warnings, particularly in systems that alert drivers to relatively low-urgency situations.

Adaptive cruise control (ACC) represents a rapidly emerging in-vehicle technology that has the potential to enhance driving safety. A critical factor governing the safety benefit of ACC concerns the ability of the driver to assume control of the vehicle in situations that exceed the capability of ACC. This study examined the effectiveness of various warning modalities in reengaging drivers who were likely to be distracted during severe braking situations that exceed the capability of ACC. The study compared warnings that paired a visual icon with an auditory cue, seat vibration, brake pulse, or a combination of all three cues. A total of sixty participants drove for 35minutes in the National Advanced Driving Simulator (NADS). Drivers experienced 2 severe, 4 moderate, and 8 mild braking situations. The ACC could accommodate all but the 2 severe situations without driver intervention. ACC provided a substantial benefit during mild braking lead vehicle events, enabling drivers to maintain a larger and more consistent minimum time-to-collision. In contrast to previous studies (e.g., Stanton, Young, & McCaulder, 1997), ACC did not produce a safety decrement during the severe braking situations. Only the combination of visual, auditory, seat vibration, and brake pulse led to slower brake reaction time in severe braking situations compared to drivers without ACC, but all four warning strategies led to a similar minimum time-to-collision and maximum braking. In contrast to several previous studies, these results suggest that drivers can effectively assume control when they receive a warning that the braking authority of ACC has been exceeded. Further research is needed to identify the boundary conditions that specify when drivers can successfully intervene and retake control and whether a multi-modal combination of cues can be crafted to speed rather than slow drivers' response.

The proliferation of in-vehicle information systems and the need for drivers to keep their eyes on the road suggest that auditory alerts will become increasingly common. This study examined how sound parameters affected perceived urgency and annoyance. The sound parameters investigated were overall density of a warning tone, pulse speed and type of burst used to create a warning tone. The context in which the auditory alert is presented was an additional factor. Significant effects were found for all factors. Annoyance and urgency of an alert depend on the context in which it is presented and sound parameters interact with context to affect the perceived urgency of alerts. Like urgency, annoyance displayed systematic variation as a function of warning signal parameters. These results suggest that auditory alert design should go beyond mapping perceived urgency of the alert to the urgency of messages, but should also consider a tradeoff analysis that addresses the costs of increasing annoyance. interpulse speed, the interval between pulses, to have the

Summary: U.S. teens are overrepresented in motor vehicle crashes, with the majority due to driver error; however, causal pathways remain to be elucidated. This research aimed to identify driving performance factors that might underlie newly-licensed male teens' risk. Surveys were conducted with 21 16-year-olds at the time of intermediate licensure. During the second month of licensure they completed drives in a high-fidelity simulator. Simulator scenarios allowed assessment of responses to yellow traffic lights changing to red and to a visual search task, for which previous data on older age groups of drivers were available. All teens had an A or B grade point average, previously found to be associated with lower crash and citation risk. Nonetheless, 71% reported risky driving in terms of prior unlicensed, unsupervised driving. In the simulator, 46% went through an intersection as the light turned red, compared to 33% of adults. In the visual search task, teens had shorter mean perception-reaction times and identified more targets than adults and older drivers, but similar to young drivers. Therefore, even teens with good grades, perceived to be less risky, were willing to take driving risks. Their driving performance suggests there may be subtle differences in the way recently-licensed teens drive that might predispose them to crashes. Further research of this nature can increase understanding of such differences and inform the development of more targeted intervention.