Modeling the Effects of Rainfall Intensity on the Heteroscedastic Traffic Speed Dispersion on Urban Roads
Publication: Journal of Transportation Engineering
Volume 142, Issue 6
Abstract
The heteroscedasticity refers to a collection of random variables with a subpopulation that have different dispersions from others. The variable dispersion could be quantified by measures of statistical dispersion such as standard deviation or coefficient of standard deviation. This study aims to model the effects of rainfall intensity on the heteroscedastic traffic speed dispersion on urban roads. The traffic and rainfall intensity data were collected by a selected video traffic detector and its nearest rainfall station in Hong Kong, respectively. The coefficient of variation of speed (CVS) was employed to measure the vehicular traffic speed dispersion. The analysis shows that the empirical values of CVS typically range from 0.05 to 0.2 at different traffic densities and rainfall intensities, and the exponential function provides a good fit to traffic speed data under both dry and rain conditions. A generalized function of CVS with the effects of rainfall intensity is proposed, calibrated, and validated with different sets of empirical data. The calibration and validation results show that the proposed generalized function of CVS fits well with the empirical data. The empirical findings and the generalized function of CVS proposed in this study may benefit for assessing and modeling the level-of-service performance of urban roads in Pacific Rim cities similar to Hong Kong with relatively high annual rainfall intensity.
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Acknowledgments
The work described in this paper was supported by the competitive earmarked research grant from the Research Grants Council of the Hong Kong Special Administrative Region (PolyU 152074/14E), and an internal research grant G-YZ21 from the Research Committee of the Hong Kong Polytechnic University for the Hong Kong Scholars Program, and the Research Institute for Sustainable Urban Development (RISUD) of the Hong Kong Polytechnic University (Project Nos. 1-ZVBX and 1-ZVBY). The revision of this work was also supported by Program for Young Excellent Talents in Tongji University (2014KJ014) and National Natural Science Foundation of China (71371001, 71171013, 71471013). The authors would like to thank the Transport Department of the Hong Kong Government for providing the JTIS traffic data from 2009 to 2011.
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Published In
Journal of Transportation Engineering
Volume 142 • Issue 6 • June 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Mar 11, 2014
Accepted: Oct 20, 2015
Published online: Feb 16, 2016
Published in print: Jun 1, 2016
Discussion open until: Jul 16, 2016
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