Random Effect Models to Predict Operating Speed Distribution on Rural Two-Lane Highways
Publication: Journal of Transportation Engineering
Volume 142, Issue 6
Abstract
This paper presents the results obtained from the estimation of free-flow speed on two-lane rural highways. The data used for the analysis were collected in Northwest Italy using video cameras and a laser speed gun. The model structure adopted separates the estimate of the central tendency of speeds from the typical deviations of individual speeds. Hence, in the model, the same set of variables can be used to determine both the mean value and the standard deviation of the speed distribution; the desired speed percentile is then calculated by considering the associated standard normal random variable (). Random effects (RE) were included in the model to account for the variability in time and space of the data that contain multiple measurements for the same road/section/direction and to remove any dependency between estimation errors from individual observations.
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Acknowledgments
The research work included in this paper has been made possible thanks to the joint project between the Politecnico di Torino (Italy) and the University of Maryland (US) titled: “—Advanced Models, Methods and Materials for Sustainable, Safe and Smart Infrastructures.” The authors acknowledge funding received from the Compagnia di San Paolo (Italy) and from the Politecnico di Torino under the grant, “Bando per il Finanziamento di Progetti di Internazionalizzazione della Ricerca,” approved with the Rectoral Decree n. 208 of the 24th of May, 2013. The Città Metropolitana di Torino and the Provinces of Vercelli and Alessandria are greatly acknowledged for the access to the GIS databases used to collect roadway inventory information.
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Information
Published In
Journal of Transportation Engineering
Volume 142 • Issue 6 • June 2016
Copyright
© 2016 American Society of Civil Engineers.
History
Received: Feb 19, 2015
Accepted: Dec 15, 2015
Published online: Feb 22, 2016
Published in print: Jun 1, 2016
Discussion open until: Jul 22, 2016
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