This paper aims at investigating how phone conversations may affect tactical control of the vehicle and decision-making. Twenty-four drivers (16 males and 8 females; mean age = 39.1; SD = 5.5) participated in an on-road experiment. They had to answer to phone calls using a hands-free kit and to maintain conversations while driving on motorway and in urban area. Results on motorway show that, during phone conversations, the drivers were less likely to overtake slower vehicles and stayed longer on the lane before moving back after overtaking manoeuvres. Some changes in speed behaviour were also observed as participants failed in adapting their speed to the limits when they changed. Driving errors were also more frequent while at the phone in urban area. Results on motorway show that while phoning, drivers tend to adapt their driving in a way to compensate for the additional attentional demand of the dual task of phoning and driving, by neglecting driving sub-tasks such as overtaking and adapting speed, etc. However, such behaviour also reveals difficulties to process all needed information to execute complex manoeuvres. Hard braking and errors in urban area occur as a consequence of these difficulties induced by phone communications.
