Interaction Design for Communicating System State and Capabilities during Automated Highway Driving

Abstract In this paper we focus on manual-to-automation and automation-to-manual transition scenarios in highway driving and the design of the instrument cluster (IC) in particular. Two alternative IC concepts were compared in order to find whether there are any differences in how easy they are to interpret and act according to. One IC contained two automation modes (manual and highly automated) while the other contained three modes (manual, Adaptive Cruise Control, highly automated). It was also hypothesized that traffic density may have an effect on how well the driver manages the transition scenarios. A simulator study was conducted in which 23 participants were exposed to the different IC designs (two vs. three modes) as well as the two degrees of traffic density (high, low). The main scenarios consisted of prompts for the driver when a higher degree of automation was possible to initiate, and different system-initiated takeover requests due to system limitations. The system limitations consisted in either just lateral automation being removed or both lateral and longitudinal automation being removed. Both subjective (e.g. general usefulness and intention to use) and objective measures (e.g. time to initiate a higher mode of automation) were used. The results showed that the two-mode IC resulted in faster takeover responses from the participants after full automation removal compared to when only lateral support was removed in the three-mode IC. The two-mode IC in some cases also resulted in quicker automation activation after an automation-available prompt.