The deliverable at hand describes the steps which were undertaken to develop and validate a driver and driving behaviour model for rural roads. First, an overview is given of the theoretical background relevant to these steps. Theories of human perception, information processing, decision making and action in general are included, as well as psychological theories especially developed to explain driver and driving behaviour. The second part of Deliverable D8 introduces the model which was developed based on the theoretical work summarized in the first chapter. This model describes, explains and predicts driver and driving behaviour on rural roads. The third part of Deliverable D8 summarizes the steps which were conducted to validate this driver and driving behaviour model for rural roads and to test the possibility to integrate psychological parameters in a safety performance function (SPF). Depending on the different hypotheses derived from the model, the following data sources were used for this process: existing driving studies; additional data collected based on this existing data; own additional simulator experiments; own additional driving studies with an equipped vehicle. Additionally, own laboratory experiments were conducted in a study of subjective road categorization. The results found after analysing the data collected in all these studies support the assumptions formulated in the models to a large extent. For example, it was shown that high accident rate curves are systematically underestimated concerning demand and risk. Evidence was found that this underestimation results in inappropriate speed behaviour which could cause accidents. Further on, the influence of cues and affordances in influencing driving behaviour could be shown and is reported in this deliverable exemplarily for road signs. The assumption that workload or risk is higher in high accident rate road sections, compared to low accident rate road sections was only indirectly supported by the empirical data. This finding is in line with the results of the study on subjective road categorisation. While we found in general, that these road categories influence behaviour these categories themselves are built based on affordances and cues, rather than expected workload or risk. Further, we could identify objective criteria which could be used to approximate these subjective categories. These results in turn could provide a valuable input towards harmonizing roads in Europe along selfexplaining road principles. Finally the integration of psychological variables in a safety performance function was tested. Despite of the validation process of the model was successful, it was not possible to assign numeric values to psychological parameters, which would be the prerequisite for an integration in the SPF. However, we could show that characteristic speed parameters could be used to approximate e.g. workload. The application of speed prediction models in the SPF thus allows at least a preliminary solution. By integrating the findings of our studies in future steps, the quality of these speed prediction models could be considerably enhanced. The integration of such psychological factors in speed prediction models for rural roads could ultimately result in a valid safety performance function. The most important future step to do so is to increase the number of cases (i.e. road sections) in the database to be able to derive stable parameter values. (Author/publisher)
Samenvatting