With the implementation of time headway dependent adaptive cruise control and the first successful tests of autonomous cars, the psychological aspects of preset time headways in autonomous and semi-autonomous driving are getting in to the focus of traffic psychological research. In addition to legal and security concerns, it is questionable what effects specific time headways at different speeds have on crucial drivers’ aspects like comfort, task difficulty and subjective feeling of risk. In this experimental study, the influence of different time headways at different speeds on subjective driving comfort, task difficulty and subjective risk was studied in a driving simulator. The distance between a vehicle equipped with time headway dependent adaptive cruise control to another vehicle driving ahead was varied for three different speeds. The experienced comfort, task difficulty and subjective risk during the adaptive cruise control drive were measured for every situation. Results suggest that the time headway maintained by the adaptive cruise control affects the comfort experience of the driver. Furthermore, comfortable time headways are influenced by the speed of the car. These results will be discussed in terms of their impact on the design of future adaptive cruise control systems as well as on autonomous driving.