The loading effect of using a mobile phone while driving has been investigated in the VTI driving simulator. The purpose was to find out if there are any differences between handheld and hands free phone modes, and also if the load imposed on the driver varies in different traffic environments and traffic situations. The study concerned conversation and dialing. Forty-eight drivers participated. The conversation task was a combined calculation and memory task performed ten times, while the dialing task involved dialing a nine-digit telephone number three times. The PDT method (Peripheral Detection Task) was used to measure mental workload. The participants had to respond to peripherally presented visual stimuli, and reaction time and proportion missed stimuli were recorded. The workload level was clearly increased, both during mobile phone conversation and dialing. The effect appeared in all traffic environments and the specifically designed traffic events included. In the most complex urban environment the PDT performance was remarkably poor. In this case the load imposed on the drivers was very high already for the driving task before the load from the phone task was added. Generally, the effects were equivalent for handheld and hands free phone modes. The PDT result was supported by the drivers' self-reported experience that the perceived effort did not differ between the two phone modes. It is concluded that handheld and hands free phones have equally negative implications for traffic safety, a fact that should be conveyed to society (A). For the covering abstract of the conference see ITRD E217780.
Abstract