It has become important to know whether talking on a carphone affects driving performance, and driving makes it more difficult to use a carphone like a standard fixed telephone. This chapter discusses four experiments, relevant to this question, that the HUSAT Research Institute, Loughborough, England has conducted in association with the DRIVE programme. The first study examined whether the style and structure of negotiation dialogues, held over a carphone, differed from those held face to face via a fixed telephone, or from those between a driver and a passenger in a car. Subjects were given role play scenarios, and asked to negotiate with an experimenter in similar role play. In the second study, the same experimental conditions were used, but a strictly controlled decision-making test was given to the subjects. They scored significantly lower when using the carphone. The third study again used negotiation role play, in a real road environment, but concentrated on driving behaviour, which was measured both objectively and subjectively. As in the first study, the results showed a higher mental demand from speaking and driving than from driving alone. The fourth study investigated the effect of car telephone calls on low complexity driving on a three-lane motorway with moderate traffic flow. No evidence was found for a change in driving behaviour during carphone conversations.
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