Research on the Effects of in-Vehicle Human-Machine Interface on Drivers' Pre and Post Takeover Request Eye-tracking Characteristics

In-vehicle Human-Machine Interface (HMI) plays a significant role for conditionally automated vehicles in realizing effective communications from driving automation systems to drivers during either automated driving period or control transitions. The present study aimed to investigate the effects of in-vehicle HMI on drivers' eye-tracking characteristics pre and post takeover request (TOR). A driving simulator-based experiment was conducted comparing the differences of drivers' visual behaviors with or without HMI under two TB (time budget) conditions (TB = 4 s; TB = 10 s). The visual HMI adopted in the experiments consisted of vehicle status display and a bird-view depiction of the traffic situation. Experiment results showed fixations prior to the TOR were more frequently shifted from real traffic situation to HMI which was effective in indirectly maintaining drivers' mode and situation awareness. Pre TOR entropy measures indicated a more dispersed but still ordered scanning pattern in spatial sampling. Saccadic behaviors were shown to be encouraged for a less cognitively demanded but a more visually loaded acquisition of surrounding information with the assistance of HMI. Post TOR fixation measure showed a prolonged Eyes-on-Traffic-Time (EoTT) when HMI was provided. And as a physiological indicator for mental workload, blink rate and blink latency did not show an additional increase after the issue of TOR under “with HMI” condition. We conclude that the introduction of in-vehicle visual HMI can be a valid option to support drivers in both automated driving and takeover time.