CityMobil: Human Factor Issues Regarding Highly-automated Vehicles on an eLane

In the European project ‘CityMobil’ the human factors aspects of (semi) autonomous driving are investigated. Systems in the car and in the driving environment enable the driver to drive (semi) automatically in a driving lane (eLane). One of the issues is the optimal interface for the change from automated to manual control and vice versa. Therefore, we conducted a driving simulator experiment with the aim to design and test the difference between a vocal and acoustic user interface, for a vehicle driven both manually and automatically. In the experiment the behavior of 24 drivers was observed, focusing on the transition of control and the occurrence of system errors. The performance of the transition of control was adequate for both interfaces at the beginning and ending of an eLane. In case of system failure, 15% of drivers failed to take timely control of the car for both interfaces. However if drivers regained control, they had a shorter response time to initiated the transfer of control to a manual mode with the vocal interface. Moreover, a subjective questionnaire showed that the vocal interface had a higher acceptance and perceived usability, than the acoustic interface. This study suggests that the vocal interface was preferred by the participants and can be recommended for the HMI of (semi) automated vehicles, especially when providing warnings about the system’s malfunctioning