A series of three studies examined the acoustic characteristics that contribute to a sound being unambiguously perceived as an urgent alarm within a vehicle context. In experiment 1, participants sorted a variety of sounds modeled after sounds currently in use in driver-vehicle interfaces (DVIs) into categories indicating highly critical warnings and alerts (or "alarms"), vehicle status sounds, or in vehicle social notifications. Results indicated that four criteria (peak-to-total time ratio, interburst interval, number of harmonics, and base frequency) explained 61% of the variance in categorization. From these criteria, cutoffs were determined and manipulated to create stimuli for an initial validation study. Experiment 2 results indicated that these criteria remained robust even when examined in a larger stimulus set and with different participants. Finally, Experiment 3 investigated rapid categorization under divided attention. Participants categorized alerts while driving in a desktop driving simulator and completing a secondary distracting task. Results indicate that previously defined parameter criteria and cutoffs are applicable in higher context and under load. Furthermore, sounds that met all criteria were responded to more quickly than those which met only some or no criteria, indicating that these criteria can be used to create sounds which are unambiguous and intuitive in an in-vehicle driving context.

Two experiments with 24 participants each evaluated comprehension of vibrotactile route guidance instructions via a tactile seat in a driving simulator. Vibrotactile patterns were presented from an array of 8 tactors arranged in two rows of 4 tactors located in the seat pan. A faster pulse rate and a slower pulse rate as well as four distinct locations on the tactile seat (Front-Left, Front-Right, Back-Left, Back-Right) created 8 different combinations of stimuli. Across all participants, the most consistent interpretation was that the faster pulse rate played from the back two tactors was perceived as an instruction to make the next most immediate turn while a slow pulse rate from the front two tactors was interpreted as a cue directing the user to the direction of the next eventual turn. Results have direct implications for design of effective vibrotactile and multimodal route guidance systems.

Using a visual search and decision-making task, we investigated common task switching effects on baggage screeners. Like the general population, baggage screeners perform best when there is no task switching as shown by a high sustained d’ and fast decision time. Although baggage screeners continue to improve throughout the task, task switching results in functional decay of the memory for the current decision-criterion.

Using a simulated baggage screening task, we investigated two literature-supported mitigation strategies for reducing the negative effects of task switching, namely less frequent switching and memory support. The study replicates widely reported switching effects on a complex task. The results also show that people can improve performance when provided memory support. When task switching, people can struggle to retrieve the correct task instruction due to the automatic process behind functional memory decay. Memory support reduces the negative effects of functional decay by providing people a reminder.

This paper explores the optimal location of gesture based in-vehicle technology for minimizing driver distraction, as well as the specific manipulative gestures that would accompany such gesture based in-vehicle technologies. Three different vehicle locations and ten different driver gestures were evaluated during testing. Participants in the study performed each of the gestures at all three locations, and results indicated that most individuals preferred using the steering wheel location. Participants’ responses indicated that they felt most comfortable with a repertoire of about seven gestures. Our initial findings suggest that a gesture-based interface system might be most effective when placed at the three o’clock position on the steering wheel, and when thee systems operate using a maximum of seven gestures.