Hugo Pietrantonio

A Decision-based Criterion for Selecting Parameters in the Evaluation of Pedestrian Safety Problems with the Traffic Conflict Analysis Technique

Abstract This article discusses and applies methods for developing diagnostic parameters for pedestrian traffic safety problems using the traffic conflict analysis technique (TCT) to a study of pedestrian crossings at urban signalized intersections in São Paulo, Brazil. The development of parameters has two tasks: the selection of an adequate classification of conflicts and/or segmentation of crossings, and the determination of parameters for the classes (including recommended confidence levels). Based on the US Federal Highway Administration guides for the study of vehicular conflicts, the pedestrian conflict count limits (abnormally high level of counts for problem detection) and the ratio of accidents per million conflicts (risk index and accident forecasting rate) are developed for the types of urban crossings observed in the signalized intersections of the study. Statistical methods are applied with a new decision-based criterion that could select the best classification/segmentation and the recommended confidence level to be used in applied work. Results obtained from the application of such methods to the case study are presented and discussed as an example application.

Evaluating road safety audit procedures: some questions and a new method of study

This article discusses the current views on the application of road safety audits (RSAs) as a tool for the improvement of road safety and proposes a new method of study for detailed evaluation of some features that can influence their effectiveness. This is demonstrated in the practical setting of RSAs applied to existing road reviews or inspections. Starting from a review of published sources on RSAs in different countries, a set of questions has been identified and a case study undertaken on the impact of alternative RSA procedures on its overall effectiveness. RSA effectiveness is measured both as agreement with a safety expert assessment and to an accident-based study. The main features analyzed in the case study include the type of observer used for data collection and the type of checklist used as a guide to field work. Based on an exploratory study, the performance of RSA application is evaluated using weighted indices of concordance and disagreement, and the rating of detection or omission for the observations gathered in the accident diagnosis of the safety problems at the intersection studied, supplemented by a statistical analysis of the influence of selected covariates on these scores. The main results of the case study can be summarized as clear support to team work for field observation and also to employing less-experienced personnel for field observation. The study also stresses the need for procedures/criteria for priority setting. These conclusions are useful for the selection of alternative RSA procedures in agencies responsible for promoting or enforcing RSA and in professional teams carrying out RSA tasks. Several features deserving further study are also identified.