  Despite the approaching commercialization of robo-taxis, various anxiety
factors concerning the safety of autonomous vehicles are expected to form a
large barrier against consumers' use of robo-taxi services. The purpose of this
study is to derive the various internal and external factors that contribute to
the anxieties of robo-taxi passengers, and to propose a human-machine interface
(HMI) concept to resolve such factors, by testing robo-taxi services on real,
complex urban roads. In addition, a remote system for safely testing a
robo-taxi in complex downtown areas was constructed, by adopting the Wizard of
Oz (WOZ) methodology. From the results of our tests - conducted upon 28
subjects in the central area of Seoul - 19 major anxiety factors arising from
autonomous driving were identified, and seven HMI functions to resolve such
factors were designed. The functions were evaluated and their anxiety reduction
effects verified. In addition, the various design insights required to increase
the reliability of robo-taxis were provided through quantitative and
qualitative analysis of the user experience surveys and interviews.
