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Assessment of safety effects for widening urban roadways in developing crash modification functions using nonlinearizing link functions

Title
Assessment of safety effects for widening urban roadways in developing crash modification functions using nonlinearizing link functions
Author
박준영
Keywords
Safety effectiveness; Crash modification factors and functions; Bayesian regression; Nonlinearinzing link function; Observational before-after methods; Time changes
Issue Date
2015-04
Publisher
PERGAMON-ELSEVIER SCIENCE LTD
Citation
ACCIDENT ANALYSIS AND PREVENTION, v. 79, Page. 80-87
Abstract
Since a crash modification factor (CMF) represents the overall safety performance of specific treatments in a single fixed value, there is a need to explore the variation of CMFs with different roadway characteristics among treated sites over time. Therefore, in this study, we (1) evaluate the safety performance of a sample of urban four-lane roadway segments that have been widened with one through lane in each direction and (2) determine the relationship between the safety effects and different roadway characteristics over time. Observational before-after analysis with the empirical Bayes (EB) method was assessed in this study to evaluate the safety effects of widening urban four-lane roadways to six-lanes. Moreover, the nonlinearizing link functions were utilized to achieve better performance of crash modification functions (CMFunctions). The CMFunctions were developed using a Bayesian regression method including the estimated nonlinearizing link function to incorporate the changes in safety effects of the treatment overtime. Data was collected for urban arterials in Florida, and the Florida-specific full SPFs were developed and used for EB estimation. The results indicated that the conversion of four-lane roadways to six-lane roadways resulted in a crash reduction of 15 percent for total crashes, and 24 percent for injury crashes on urban roadways. The results show that the safety effects vary across the sites with different roadway characteristics. In particular, LOS changes, time changes, and shoulder widths are significant parameters that affect the variation of CMFs. Moreover, it was found that narrowing shoulder and median widths to make space for an extra through lane shows a negative safety impact. It was also found that including the nonlinearizing link functions in developing CMFunctions shows more reliable estimates, if the variation of CMFs with specific parameters has a nonlinear relationship. The findings provide insights into the selection of roadway sites for adding through lanes. (C) 2015 Elsevier Ltd. All rights reserved.
URI
https://www.sciencedirect.com/science/article/pii/S0001457515001001https://repository.hanyang.ac.kr/handle/20.500.11754/105991
ISSN
0001-4575; 1879-2057
DOI
10.1016/j.aap.2015.03.025
Appears in Collections:
COLLEGE OF ENGINEERING SCIENCES[E](공학대학) > TRANSPORTATION AND LOGISTICS ENGINEERING(교통·물류공학과) > Articles
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