| Title | Using Multivariate Crash Frequency Model to Analyze Urban Lane Width and Vehicle Composition to Road Safety |
| Year | 2018 |
| Degree | Master |
| School | Department of Transportation and Logistics Management National Chiao Tung University |
| Author | |
| Summary | Taiwan’s traffic condition on urban arterials is mixed traffic, and the type of urban development is mixed-use, which caused the mechanism of lane width on crashes is different from previous literature. Besides, previous crash frequency models usually didn’t separate crashes by different severities or types, leading to biased estimates. This study seeks to explore the impact of lane width and vehicle composition on different types of crashes, and to develop urban road crash modification factors. The study data set includes crashes, roadway attributes and traffic volume of Taipei City from 2012 to 2016. However, there are many challenges to accurately evaluate the effects of lane width on the numbers of crashes. These challenges mainly include: (1) low sample mean; and (2) correlation among crash types and severities. A multivariate Poisson log-normal model is proposed in response to these challenges by simultaneously modeling crashes frequency in terms of different crash types or severities. Among findings are: (1) the correlations between crashes of different severities, types and types of vehicle involved are high; and (2) the wider of outer lane, the greater number of crashes when the number of lane is 2 or 3; and (3) access points, bus stops, left turn lanes and higher ratio of motorcycle tend to result in weaving or parallel driving events, which increase the risk of crash; while the slow lanes provide a diverging environment to reduce it. |
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