Hands-free mobile phone speech while driving degrades coordination and control

Using a closed-circuit driving track environment, we investigated the influence of using a hands-free mobile (or cell) phone on various biomechanical and perceptual factors that underlie the control of driving. Results showed that in three tasks representative of everyday driving conditions, the perceptual control of action was compromised when compared to a control condition where no mobile phone conversation was present. While conversing, critical control actions related to braking were postponed on approach to a corner. During controlled braking, as when approaching a stationary car at a traffic light, the degree of braking was reduced and braking style was altered in a non-optimal manner. During an obstacle avoidance task, car dynamics were affected as a result of the conversation. Interpretation of the results is motivated by the ecological approach to perception-action and the theory of affordances. It is concluded that a driver's sensitivity to prospective information about upcoming events and the associated perception and awareness of what the road environment affords may both significantly be degraded when simultaneously using a handsfree mobile phone. Implications for intervention and policy are discussed. (C) 2004 Elsevier Ltd. All rights reserved.