Doctoral Dissertations

Date of Award

8-2008

Degree Type

Dissertation

Degree Name

Doctor of Philosophy

Major

Civil Engineering

Major Professor

Lee Han

Committee Members

Stephen H. Richards, Arun Chatterjee, Xuedong Yan, Bruce Ralston

Abstract

The safety benefit of Stop-sign treatment employed at passive highway rail crossings has been a subject of research for many years. The objective of this study is to assess the effectiveness and impacts of Stop-sign treatment on crossing safety. This research addresses safety at public highway-railroad grade crossings across the United States within a 26-year period of accident history for Crossbucks-only controlled crossings that were upgraded to Stop-sign control.

This study utilized Federal Railroad Administration (FRA) accident data to investigate average accident frequency at crossings with the two different types of passive-crossing sign controls. The research database was created by locating and extracting records relevant to public crossings, excluding private, pedestrian, and grade-separated crossings.

The research followed a three-part approach. The first part of the study used statistical analysis methods to evaluate accident frequencies for target crossings. Analysis of accident frequencies that occurred during both phases of installation history indicates that accidents were significantly lower during the Stop phase than during the Crossbucks-only phase.

The second part of the research used logistic regression modeling to further evaluate accident risks and factors at these two types of passive railroad grade-crossing treatments. Results of the logistic regression were reported according to the main effect of various factors and variation of those factors. An analysis of covariance was performed between factors of statistically significant contribution.

The third part of the research synthesized data into a set of models designed to predict safety performance of Stop signs and Crossbucks. Negative-binomial regression modeling was used to identify attributes and limits for which Stop signs showed superior safety benefits.

This research concludes that Stop controls did lead to discernable reduction in the accident rate, particularly for the period since ISTEA (1991). Annual accident frequencies were significantly higher during the period when crossings were controlled by Crossbucks only.

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