Twenty participants completed test rides in a normal and an Automated Highway System (AHS) vehicle in a driving simulator. Three AHS conditions were tested: driving in a platoon of cars at 1 sec and at 0.25 sec time headway and driving as a platoon leader. Of particular interest was overreliance on the automated system, which was tested in an emergency condition where the automated system failed to function properly and the driver actively had to take over speed control to avoid an uncomfortable short headway of 0.1 m. In all conditions driver behavior and heart rate were registered, and ratings of activation, workload, safety, risk, and acceptance of the AHS were collected after the test rides. Results show lower physiological and subjectively experienced levels of activation and mental effort in conditions of automated driving. In the emergency situation, only half of the participants took over control, which supports the idea that AHS, as any automation, is susceptible to complacency.

Ref: What Will Happen When Your Driverless Car Crashes? – Paleofuture