Recent innovations in microcomputer and display technology have resulted in sophisticated route guidance systems that help drivers in selecting and maintaining routes. However, the efficacy of these systems still depends on the drivers' cognitive characteristics. The characteristics imply constraints on what kind of information drivers need and how such information can be best displayed. In general, it is recognised that voice guidance makes the driving task easier and safer. In particular, drivers need guiding information before every required turn. The most obvious criterion of effectiveness of guiding information is the time left available before the manoeuvre. Using the driving simulator SHERPA, the authors tested the influence of time to manoeuvre an automobile drivers' behaviour at the approach of two reorientation intersections. The authors designed four conditions of verbal announcements involving various degrees of anticipation with respect to the locations where the directional changes should occur. The authors intended to identify the announcements allowing for the most appropriate anticipatory behaviour with the lowest risk of accidents. Behavioural measures included velocity, pressure on the brake and the clutch, acceleration of the steering wheel, and position of hands on the steering wheel. The results showed that two of the four conditions did not allow drivers to anticipate their actions in the intersection and resulted in dangerous behaviour. The other two which approximated information deliverance by road signs, allowed drivers to anticipate more effectively. However, none of the latter announcements taken separately were really optimal. In one case, the drivers tended to forget information, while in the other, the announcements failed to provide confirmation of previously memorised instructions. A combination of types of announcements should thus be recommended. Based on the results of this investigation, the authors propose specifications that designers might use to develop an effective and safe guidance system. (A)
Abstract