There are several human factor concerns with highly autonomous or semiautonomous driving, such as transition of control, loss of skill, and dealing with automated system errors. Four CityMobil experiments studied the eLane concept for dual-mode cars, and the results of one are described. The open eLane concept brings together road infrastructure and technical developments in vehicle automation to allow automated driving. The goal for the driving simulator experiment was to design and test the difference between a vocal and an acoustic user interface for a dual-mode vehicle driven both manually and automatically. In the experiment (n = 24), driver behavior was observed with a focus on the transition of control and the occurrence of system errors. Performance of transition of control was adequate for both interfaces at the beginning and end of an eLane. In the case of system failure, 15% of drivers failed to take control of the car in time for both interfaces. However, of those who did regain control, drivers with the vocal interface were faster. Moreover, a subjective questionnaire showed that the vocal interface was perceived as more positive than the acoustic interface. The study suggests that the vocal interface was preferred by participants and can be recommended for the human-machine interface of dual-mode vehicles, especially for providing warnings about system malfunctioning.