The car phone equipment rate is increasing. However, one may ask if using a phone, even if it is handsfree, while driving does not not induce any additional risks for the driver. The aim of the present study is to experimentally assess the potential risk on road safety when using a handsfree phone while driving in situation of interactive conversation.

This exploratory research was carried out on an interactive driving simulator and was based on about 40 routes performed by 17 subjects.

In a first step, the observation of speed variations induced by the use of a phone brings two types of reaction into prominence :​ 1) no effect, and 2) a more rigid driving behaviour. This latter is shown by a speed increase or decrease, or by a longer period of oscillations around the required speed, or even by a total loss of speed control. These reactions were compared to answers to a questionnaire asking for the causes of difficulties encountered and how the driving task was disturbed by phoning while driving, and vice versa. This comparison has allowed us to see how the subjects have managed the dual task;​ in most cases, they have used a time sharing strategy during which the main task, i.e. driving, is often perturbed by the second one, i.e. phoning.