Evaluation of Autonomous Vehicles and Smart Technologies for Their Impact on Traffic Safety and Traffic Congestion
While Highly Automated Driving Systems (HADS) are expected to become increasingly common on roadways, there remain scenarios where human drivers may need to take over control under certain conditions. Using a virtual reality (VR) driving simulator, researchers studied key factors influencing driver performance and evaluated specific differences in driver performance during takeovers from HADS versus current manual driving. A total of 37 individuals participated in the VR simulator study and completed questionnaires to gauge attitudes about driving automation.
Participants were virtually seated in a 4-door sedan and drove a counterbalanced set of eight 17.5-mile test scenarios, four with full manual driving control and four with takeover conditions under automated driving. Participants were instructed to drive in the center lane and were presented with scenarios requiring maneuvers around three types of obstacles: reduced speed S-curves (left-right or right-left), orange traffic cones, or an overturned vehicle, approximately six seconds ahead. In the automated driving scenario, a visual and auditory takeover request was presented to the driver six seconds prior to the event. The distance from the obstacle (Distance to Contact; DTC) and time to obstacle (Time to Contact; TTC) when the obstacle maneuver was initiated and completed were recorded. After completing the eight scenarios, participants completed a questionnaire using a Likert-type scale between 1 (strongly disagree/negative) and 6 (strongly agree/positive) to measure specific attitudes about driving automation, including trust and overall views.
- Participants performed safer obstacle avoidance maneuvers in the takeover from automation condition than in the fully manual condition, as indicated by farther DTC and longer TTC. The request for takeover allowed avoidance maneuvers to be initiated and completed by drivers with more time and distance remaining before obstacle contact.
- At initiation of the avoidance maneuver, DTC was 2 percent farther and TTC was 20 percent longer with the takeover request, as compared to fully manual driving. At the completion of the avoidance maneuver, DTC was 35 percent farther and TTC was 53 percent longer with the takeover request as compared with fully manual driving.
- Vehicle speed was on average around 17 percent slower when performing obstacle avoidance maneuvers after a takeover from automation than in fully manual driving.
- Questionnaire results show that participants on average consider that highly automated driving will be easier than manual driving (4.27 out of 6) but have neutral attitudes (between 3-4 out of 6) on most questions about their views of driving automation as a whole.