Evaluation of safety performance in urban networks: a case study of Fortaleza city/Brazil

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Caio Assunção Torres
Flávio José Craveiro Cunto

Road safety performance is usually not objectively considered in traditional transportation planning process due to a myriad of problems regarding the methodologies to estimate the number of accidents on urban transportation networks. Conventionally, efforts regarding the assessment of road safety performance have been accomplished with the use of safety performance functions (SPF). This type of statistical modeling approach has been very useful when focused on isolated road entities such as intersections and road segments, mostly because it can reasonably deal with some of the stochastic problems related to the rare and random nature of crashes. Advances in data collection and spatial manipulation as well as modeling techniques have been fostering studies to support the use of SPF for safety assessment of urban networks. This paper investigates the use of SPF as a tool to evaluate different transportation planning scenarios for urban road networks. Initially, a geographic crash database, geometric and operational attributes of the network database were consolidated on a Geographic Information System (GIS) platform and then used for developed SPF for links (road segments) and nodes (intersections) of the urban road network of Fortaleza city, Brazil. Calibrated functions were implemented on a sample network modeled using macroscopic model TransCAD. A residual analysis was performed using observed and estimated crash frequency. Finally, tree hypothetical scenarios were applied to the network in order to explore the sensitivity of the safety performance obtained from this modeling exercise. The results shows that possible to plan for the implementation of additional measures to minimize the increase in crashes for the critically affected in road network, links and nodes within SPF. Some important pitfalls and limitations in the application of SPF on computerized transportation networks were highlighted in the research. The most important is the dependence of estimation of accidents with AADT of the estimation process Although additional work needs to be done regarding the integration of traffic safety models into the urban transportation planning process, the product of this research should help other researchers pursue interesting and useful areas of research that would help, at the planning stage, to reduce the number and the severity of collisions on urban roads.

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