Relationship between Lane Width and Safety along Urban Expressways in Shanghai
Publication: Journal of Transportation Engineering, Part A: Systems
Volume 145, Issue 3
Abstract
Safety issues along urban expressways have gained increasing attention for their direct impact on traffic operation, especially after a substantial amount of reconstruction work that altered the cross section designs to create additional travel lanes. Despite the obvious benefit of higher capacity, the safety effects related to the variety of lane widths are uncertain. This paper examines the impact of lane widths on crash frequency for various types of crashes based on field data obtained from the expressway system in Shanghai. Four data sets were manually collected, including crash data, traffic flow data, lane width data, and geometric design data. Based on these data, safety performance functions (SPFs) were developed using negative binomial regression models. Crash modification factors (CMFs) were built upon the SPFs to quantify the impact of various lane widths on crash frequency for each crash type of interest. Specifically, we considered five cases in this paper: total crashes, two-vehicle crashes, multivehicle crashes, crashes under congested flow conditions, and crashes under noncongested flow conditions. In addition, lane width data are grouped into three categories in our models: undersized lanes (average lane width ), standard-sized lanes (average lane width around 3.45 m), and oversized lanes (average lane width ). The standard-sized lanes are always found to have the lowest crash frequency among all five cases; both undersized and oversized lanes are found to increase crash frequency, that is, total crash frequency for undersized and oversized lanes increased by 1.9 times and 1.34 times, respectively.
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Acknowledgments
The authors would like to thank the Natural Science Foundation of China (Grant No. 51422812) and the Fundamental Research Funds for the Central Universities for supporting this research.
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Published In
Journal of Transportation Engineering, Part A: Systems
Volume 145 • Issue 3 • March 2019
Copyright
©2018 American Society of Civil Engineers.
History
Received: Oct 29, 2014
Accepted: Aug 13, 2018
Published online: Dec 31, 2018
Published in print: Mar 1, 2019
Discussion open until: May 31, 2019
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