Development of crash modification factors for bridge rail improvements

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Date
2015
Journal Title
Journal ISSN
Volume Title
Publisher
University of Alabama Libraries
Abstract

Bridge components such as bridge railings are safety features designed to protect drivers. The guidelines for those safety features have recently been updated to accommodate for the increase in vehicle size. One method to bring non-conforming bridges up to current standards is retrofitting. The objective of this research is to determine the safety effectiveness of retrofitted bridges that have been updated to current standards. Bridge data and bridge related crash data from historical data for Alabama were collected. The data was cleaned and processed in a geographic information system. The remaining data was used in the development of Safety Performance Functions (SPFs) and Crash Modification Factors (CMFs). The SPFs used in this study were developed to predict crash frequency and severity in future years based on roadway and geometric characteristics. The SPFs for general crashes were developed using Negative Binomial. The SPFs for severity of single vehicle crashes were developed using both Negative Binomial and Conway-Maxwell-Poisson. The SPFs used in this study were developed in a connected study and used in this study as part of the CMF development. After obtaining the various prediction models for general crashes and for single vehicle severity crashes, the research utilized the information obtained from them in the development of the CMFs. This research employed the empirical Bayes (EB) before-after approach to develop the CMFs. The CMFs were a measure of effectiveness for retrofitting bridge railings to meet current standards. CMFs were determined for both the general crash and for severity of single vehicle crashes. The findings of this research were that retrofitting bridges to conform to the current standards results in a reduction in crashes and a reduction in the severity of crashes. The findings of this research can aid in the decision making process involving bridge railing improvements

Description
Electronic Thesis or Dissertation
Keywords
Engineering, Civil engineering
Citation