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Speed, speed variation and crash relationships for urban arterials

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journal contribution
posted on 05.06.2018 by Xuesong Wang, Qingya Zhou, Mohammed Quddus, Tianxiang Fan, Shou'en Fang
Speed and speed variation are closely associated with traffic safety. There is, however, a dearth of research on this subject for the case of urban arterials in general, and in the context of developing nations. In downtown Shanghai, the traffic conditions in each direction are very different by time of day, and speed characteristics during peak hours are also greatly different from those during off-peak hours. Considering that traffic demand changes with time and in different directions, arterials in this study were divided into one-way segments by the direction of flow, and time of day was differentiated and controlled for. In terms of data collection, traditional fixed-based methods have been widely used in previous studies, but they fail to capture the spatio-temporal distributions of speed along a road. A new approach is introduced to estimate speed variation by integrating spatio-temporal speed fluctuation of a single vehicle with speed differences between vehicles using taxi-based high frequency GPS data. With this approach, this paper aims to comprehensively establish a relationship between mean speed, speed variation and traffic crashes for the purpose of formulating effective speed management measures, specifically using an urban dataset. From a total of 234 one-way road segments from eight arterials in Shanghai, mean speed, speed variation, geometric design features, traffic volume, and crash data were collected. Because the safety effects of mean speed and speed variation may vary at different segment lengths, arterials with similar signal spacing density were grouped together. To account for potential correlations among these segments, a hierarchical Poisson log-normal model with random effects was developed. Results show that a 1% increase in mean speed on urban arterials was associated with a 0.7% increase in total crashes, and larger speed variation was also associated with increased crash frequency.

Funding

This study was jointly sponsored by the Science and Technology Commission of Shanghai Municipality (15DZ1204800), the Chinese National Science Foundation (51522810), the 111 Project (B17032)and the National Engineering Laboratory for Integrated Optimization of Road Traffic and Safety Analysis Technologies.

History

School

  • Architecture, Building and Civil Engineering

Published in

Accident Analysis and Prevention

Volume

113

Pages

236 - 243

Citation

WANG, X. ... et al, 2018. Speed, speed variation and crash relationships for urban arterials. Accident Analysis and Prevention, 113, pp.236-243.

Publisher

© Elsevier

Version

AM (Accepted Manuscript)

Publisher statement

This work is made available according to the conditions of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0) licence. Full details of this licence are available at: https://creativecommons.org/licenses/by-nc-nd/4.0/

Acceptance date

23/01/2018

Publication date

2018-03-07

Notes

This paper was published in the journal Accident Analysis and Prevention and the definitive published version is available at https://doi.org/10.1016/j.aap.2018.01.032.

ISSN

0001-4575

Language

en

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