Projecting the planned trajectory of a Level-2 automated vehicle in the windshield: Effects on human drivers' take-over response to silent failures.

To enhance the take-over performance by human drivers of Level-2 automated vehicles (AV), we developed a design concept that presents the AV's planned trajectory as augmented reality in the windshield. We hypothesized that, even when the AV does not release a take-over request before a potential crash (i.e., silent failure), the planned trajectory would allow the driver to foresee the crash and enhance the take-over performance. To test this hypothesis, we conducted a driving-simulator experiment where participants monitored the driving status of an AV with or without the planned trajectory in the context of silent failures. The results showed that, when the planned trajectory was projected in the windshield as if it were an augmented-reality display, the crash rate decreased by 10% and the take-over response time decreased by 825 ms compared to when the planned trajectory was not provided.

Usability enhancement based on usability heuristics: An examination of the underlying mechanism utilizing the psychological-refractory-period paradigm.

User Interface (UI) design practices often abide by popular usability heuristics such as Nielsen's (1994) "10 usability heuristics for user interface design" or Gerhardt-Powals' (1996) cognitive engineering principles. To examine the underlying mechanism of user performance enhancement by following some of these usability heuristics, we compared user performance between two device conditions: one representing design practices following two selected sets of usability heuristics (experimental condition) and the other without following them (control condition). As a research framework, we adopted the psychological-refractory-period (PRP) paradigm along with the locus-of-slack logic, a well-established dual-task paradigm for examining the nature of cognitive benefits caused by experimental manipulations. Results showed that the experimental-device condition that followed the usability heuristics yielded faster performance than the control condition, especially when the stimulus-onset-asynchrony between the two tasks was long than when it was short. According to the locus-of-slack logic, these results suggest that the nature of cognitive benefits caused by following the usability heuristics is more likely to be due to shortening of the response-activation stage (rather than the response-selection stage). These findings suggest that following the two usability heuristics tends to facilitate a specific stage of the information processes more than other stages.