Simple Safety: Tactile Directional Stimuli Improve the Safety of Takeover Requests in Semiautonomous Vehicles

A rapid and safe re‐engagement with the driving task is crucial for maintaining high performance and ensuring safety in semiautomated vehicles. Previous studies relied on audio, visual, or tactile alerts for takeover requests (TORs). Existing tactile systems for drivers typically target proximate objects (e.g., surrounding vehicles), while the potential of tactile stimuli to direct attention toward dynamic regions of interest is underexplored. Reaction time has been used throughout the literature as a primary measure of the effectiveness of a solution. Drivers might react quickly, yet they can still lose control of the vehicle. Thus, measuring the safety of the driver’s remedial action, when a TOR is issued, is a more comprehensive manner for estimating the effectiveness of a solution. A TOR Safety Score is introduced here as the number of crashes and vehicle drifts after a TOR, and a novel tactile method for pointing to the region of interest during a TOR is presented. Thirty volunteers participated in its evaluation using a driving simulator, either with or without a directional tactile stimulus. Whether directional tactile memory persists and aids drivers’ performance during TORs was measured. The findings reveal that the use of a directional tactile stimulus consistently leads to a higher Safety Score in both Level 2 and Level 3 driving. TORs were safest when the directional tactile stimulus was administered five minutes before the TOR. Drivers’ performances decreased as the time of the directional tactile stimulus administration before the TOR increased, up to 10 min before the TOR, particularly in more demanding Level 3 scenarios. These findings can aid the design of the human–vehicle interface of semiautonomous vehicles.