Usage and effectiveness of Adaptive Cruise Control: a focus group study

A wide number of Advanced Driver Assistance Systems (ADAS) have been developed with the objective of helping the driver in the primary driving task. Among the first ADAS available on vehicles, Adaptive Cruise Control (ACC) assists the drivers in keeping the desired speed and headway to the preceding vehicle by controlling fuel flow or by slightly braking. Through the partial automation of the longitudinal driving task, ACC could reduce the driver's workload and, therefore, increase drivers' comfort. However, a new task will be introduced for the driver: the monitory of the system. Based on the studies already carried out, there is concern in the academic community about the possible negative effects of ACC on road safety (e.g., reduction of situation awareness and behavioural adaptations to the system). Furthermore, there is a lack of research performed with real users of the system as participants. In order to fill this gap, the first step on that direction could be represented by the subjective assessment of drivers' behaviours and patterns of use with the system. In this context, this study aims at investigating the perceptions of ACC drivers concerning the usage and effectiveness of ACC. Two focus group sessions were carried out in Braga (Portugal) with ACC users aged 33-61 years. Results showed that drivers use the system in high speed roads and with stable or low traffic conditions. Drivers are, globally, satisfied with the system but pointed out that, in some situations, the system is not comfortable and they prefer to deactivate it. Some positive effects of ACC were mentioned but, on the other hand, improper usages of the ACC were also revealed by the participants. Finally, concern was shown with respect to the drivers travelling behind the car equipped with ACC. Further research confirming or rejecting the finding is suggested.