The influence of environmental factors on speed choice

Speed and homogeneity of speed are important factors for safe and sustainable traffic. Lower speeds and more homogeneous speeds are safer and cause less pollution. Speed behavior is influenced by environmental factors as well as by personal factors. Understanding the relation between speed behaviour and the influencing factors offers clues for appropriate countermeasures against inappropriate and excessive speed. This study investigates the relation between speed and environmental factors for single lane rural roads, one of the most hazardous road types in the Netherlands. The study uses data from two provincial road authorities. Data consists of speed data from loop detectors, road design characteristics, characteristics of the road environment, and police enforcement. The first objective of this study is to validate the outcomes of earlier studies reported in literature, such as photograph studies and self reported speed behaviour studies. In this study, the influence of the same external factors on percentile speed measures and homogeneity measures from speed loops are investigated. A second objective is to refine the credibility models by adding external factors, if relevant. The results of this study replicate some of the results that were found earlier, but not all. No additional factors were found; results and consequences will be discussed.