Background

The work described in this report is part of a research programme aimed at developing methods of identifying and improving high-risk interactions between vehicles, roading situations, and drivers. To date this has involved the use of high-resolution video analysis, computer simulation, and full scale field testing. The research objectives guiding this work employ a systems approach to understanding and improving our road transport system; addressing vehicle performance (stability, tracking etc), road configurations (signage, geometry etc) and driver behaviour collectively. Part of this approach has been directed at analysis of the driver’s perception-decision-action cycle in responding to various driving situations. As it has been hypothesised that driver attentiveness is a key variable affecting the time course of the perception-decision-action cycle (Neisser, 1976; White & Thakur, 1995), our work has included analysis of driver attentiveness in terms of: 1) a driver’s momentary level of cognitive workload (overall demands on cognitive resources), and 2) the proportion of those resources dedicated to the driving task (as reflected in the driver’s momentary situation awareness). Within this context, our previous research examined drivers ’ reactions to road hazards, maintenance of speed and following distances, and the differential properties of explicit (attentional) and implicit (perceptual) features of road safety engineering solutions across a range of traffic and road situations (Charlton & Baas, 1998; Charlton, Mueller, &amp