Relationship between Predicted Speed Reduction on Horizontal Curves and Safety on Two-Lane Rural Roads in Spain
Publication: Journal of Transportation Engineering
Volume 140, Issue 3
Abstract
According to different studies, speed reduction is considered one of the major factors in contributing road safety. For that reason, several guidelines have been recommended for maximum desirable speed reductions from tangents to horizontal curves and for maximum differentials between design and operating speeds on horizontal curves. The Interactive Highway Safety Design Model (IHSDM) Design Consistency Module presents an analysis of the relationship between speed reduction and crashes for horizontal curves on U.S. two-lane rural highways. This paper presents the relationship between speed reduction and crashes for horizontal curves on Spanish two-lane rural roads. A model for using regression analysis to predict crashes is presented. Exposure, curve length (CL), and difference in 85th-percentile speeds () between successive tangents and horizontal curves, as well as between successive curves, are used. The model’s coefficients were different from the ones obtained for U.S. highways, although the values of the goodness-of-fit criteria were similar. In addition, the relationship between crashes and different speeds is analyzed, taking the difference in speed as a speed differential not exceeded by 85% of the drivers traveling under free-flow conditions (), instead of considering it as . The two models ( versus ) give very similar results.
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Acknowledgments
The authors express their acknowledgment to the Spanish General Directorate of Traffic (DGT), the Dirección General de Carreteras de la Consejería de Fomento y Vivienda of the Andalusian regional government, and the Staff of Sistema de Información de Carreteras de Andalucía (SICA) for supporting this research. Without the data they provided, this research would not have been possible. Support from Spanish Ministry of Economy and Competitiveness (Research Project TRA2012-37823) is also gratefully acknowledged.
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Published In
Journal of Transportation Engineering
Volume 140 • Issue 3 • March 2014
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© 2013 American Society of Civil Engineers.
History
Received: Dec 21, 2012
Accepted: Aug 28, 2013
Published online: Aug 30, 2013
Published in print: Mar 1, 2014
Discussion open until: May 5, 2014
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