Driver behavior around driver readiness alerts versus attention reminders while using Tesla Autopilot.

INTRODUCTION: Tesla's Autopilot attention reminders typically follow escalation sequences that start with visual-only alerts, but some alerts bypass this escalation pattern and begin with the visual-audible alert phase. This study's aim was to understand what triggered those alerts and how drivers behave around them over time. METHOD: We analyzed 283 alerts that bypassed the visual-only phase from 13 drivers who used a 2020 Tesla Model 3 as their personal vehicle for 4 weeks. We identified roadway features and driver behaviors that were present around these alerts. RESULTS: Alerts most often occurred on high-speed, limited-access roads and during the daytime. Gores, lane splits or merges, and single-lane roads were most likely to be present leading up to these alerts. Unlike the attention reminders we analyzed in an earlier paper, which followed the typical sequence, the alerts bypassing the visual-only phase did not change significantly over time either in frequency or duration. Drivers were more likely to have at least one hand on the wheel around these alerts than around attention reminders. Drivers often looked at the center stack display during the alerts. Secondary activity unrelated to driving was more prevalent than driving-related activity throughout the study. CONCLUSIONS: Despite their similarity to attention reminders, alerts that bypass the visual-only phase appear more closely associated with the environment than with driver behavior. They may serve as driver readiness prompts when scenarios that Autopilot finds difficult appear. Driver readiness alerts did not undermine attention reminder efficacy or Autopilot use; however, neither alert type extinguished undesired driver behavior.