This chapter reports a Swedish project on stress measurement in relation to Road Traffic Informatics (RTI) success, in the PROMETHEUS programme. 'Negative stress' (stress with negative effects) in a driver may occur from a combination of: (1) more or less permanent 'background stress' due to difficult personal circumstances' (2) temporary background stress, for example from time pressures; (3) 'traffic stress' or acute stress, due to severe and uncertain traffic conditions. These types of stress are believed to interact to a combined stress level, and are also difficult to distinguish. Different RTI functions can potentially have many positive effects in reducing negative stress. As it may not be possible to to measure stress directly with physiological techniques, the authors developed a subjective method of rating stress, combining ratings into a 'stress-index'. In their pilot study, an RTI function was simulated by 'letting the road imitate' an RTI that helps drivers to overtake other vehicles safely. The study was performed in Autumn 1990 on Highway 40 in West Sweden; 89 drivers were asked three questions about their stress; 45 drivers were interviewed on a two-lane section and 44 on a three-lane section. The 'road and traffic' contribution to stress for the former section was found to be significantly higher. The authors suggest further studies to improve subjective stress measurements.
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