Advancing road safety analysis: new methods for evaluating and measuring safety

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The importance of reducing the social and economic costs of road collisions cannot be overstated. Therefore, considerable research has been undertaken recently and advances have been made in road safety analysis. These developments are creating a movement towards the explicit consideration of safety in road planning and design. However, associated with these advances are a series of obstacles that are inhibiting the future direction of road safety. There is a lack of complete understanding of the complex interaction of collision factors and how safety measures work. The main contribution of this research will be the development of novel methods that advance this understanding. This proposal focuses on three issues: i) evaluating and validating surrogate safety measures; ii) calibrating road design codes using reliability methods and establishing linkage with collisions and iii) addressing key issues related to the evaluation of intervention effectiveness. The research attempts to contribute to traffic safety research in several ways. It tests and validates the use of traffic conflicts as surrogate safety measures. This should address the main shortcomings of the traffic conflict technique, lead to a wider acceptance of the use of collision surrogates, and offer a better understanding of vehicle collision failure mechanism, particularly the collision-avoidance behavior of drivers which should help the diagnosis and remedy of the safety problems. As well, the research should lead to a wider application of reliability analysis in road design through establishing relationships between the reliability index and the expected collision frequency and providing road design standards that ensure a consistent and accepted risk levels. Finally, the research will develop novel methods for road safety intervention analysis that provide better understanding of the role of model parameters and their effects on the estimation of treatment effectiveness. Current evaluation techniques assume constant countermeasure effectiveness that does not change with time which is unrealistic. Given the way future benefits are discounted to present values, the results of using countermeasure effectiveness which changes with time can significantly impact the cost effectiveness of safety measures.