| This research develops and tests a conceptual framework for evaluating and selecting exposure measures in safety applications, particularly pedestrian safety. The concept and applications of exposure are systematically explored through a broad review of research and applications in several contexts, including transportation, mechanical, and health systems. A consistent definition of exposure is developed based on trials which may lead to failures; chance set-up which is the determinant of failure risk, and the progress of the system toward its objective in time and space. Based on this definition, a framework is developed for analyzing, evaluating, and selecting exposure measures, based on the criteria of conceptual validity, collection feasibility, measurement reliability, and cost-effectiveness.; Exposure measures which have been used in pedestrian and traffic safety are reviewed within this framework, both to test the conceptualization and assess the measures. This framework can be used to guide the choice of exposure measures by (a) explicitly defining the problem of interest, (b) understanding the system operations and failure mechanisms, (c) characterizing exposure based on the conceptual definitions (trials, chance set-up, progress), (d) evaluating measurement options, and (e) identifying and assessing preferred measures. |
