Shared intention and shared awareness for conditional automated driving: An online, randomized video experiment

In conditional automation for automated vehicles (AVs), drivers are tasked with remaining vigilant and ready to assume control should the system encounter a malfunction. However, little to no information is provided to the driver either about the AV's intended maneuvers or the AV's awareness of potential threats in the surrounding environment. To address this research gap, the present study proposes 2 human-machine interaction (HMI) concepts: Firstly, the shared intended pathway (SIP), which presents a forecast of the AV's intended maneuvers and, secondly, object recognition bounding boxes (ORBBs), which place transparent blue squares around other road users likely to contribute to a crash.

An online experiment with both within- and between-group factors tested 2 HMI designs: One with both SIP and ORBB and one with SIP only. Six videos were presented sequentially, each depicting 10 to 15 s of automated driving, to 394 participants (M_age = 28.24 years, 64% male) in Australia. Participants monitored the AV in each of the videos, which were presented in 1 of 3 randomized conditions: no HMI display, SIP only, or SIP + ORBB. Questions after each video measured trust, situational awareness, stress, and user acceptance, as measured by the technology acceptance model (TAM) about user acceptance.

Results suggest that SIP is beneficial in conditional automation monitoring, in terms of reduced stress, increased perceived usefulness, and future intentions to use AVs. Further, ORBB presence increased participant ratings of perceived usefulness and intentions to use AVs compared to no ORBB. The findings also provided support for the TAM, because perceived ease of use and perceived usefulness were found to be significant positive predictors of future intentions to use AVs.

The current study provides some evidence to suggest that SIP may be beneficial in automated driving. However, further on-road testing of HMI displays for AVs that include SIP and ORBBs are needed to enhance the user experience and acceptability of AVs and to provide more ecological validity.