Low-Speed Horizontal Curve Friction Factors
Publication: Journal of Transportation Engineering
Volume 131, Issue 2
Abstract
This project was a pilot study to examine side friction values for the geometric design of low-speed urban horizontal curves. The friction factors calculated from measured curve radius, pavement cross slope, and vehicle speed within the curve were compared with those in the 2001 A policy on geometric design of highways and streets. The findings from the five study sites suggest that the current low-speed urban side friction values may be overly conservative, in that a sizeable proportion of drivers can exceed the intended design speed. The average friction factors calculated for different categories of passenger cars differed among the categories. A significant amount of geometric irregularities, perhaps due to either construction or maintenance practices, were found among the curves examined. The paper also contains practical advice for those engaged in future field data collection.
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Acknowledgments and Disclaimer
The support of the Arkansas State Highway and Transportation Department (AHTD), the Mack-Blackwell Transportation Center, and the Department of Transportation, University Transportation Centers Program made this research possible. The writers appreciate the computer programming performed by Mr. David Li. The contents of this paper reflect the views of the writers, who are responsible for the facts and accuracy of the information presented herein. The contents do not necessarily reflect the official views or policies of the Arkansas State Highway and Transportation Department or the Federal Highway Administration.
References
American Association of State Highway and Transportation Officials (AASHTO). (2001). A policy on geometric design of highways and streets, Washington, D.C.
Barnett, J. (1936). “Safe side friction factors and superelevation design.” Proc., HRB, Vol. 16, Highway Research Board, Washington, D.C., 69–80.
Bonneson, J. A. (1999). “Side friction and speed as controls for horizontal curve design.” J. Transp. Eng., 125(6), 473–480.
Bonneson, J. A. (2000). “Superelevation distribution methods and transition designs.” National Cooperative Highway Research Program Report 439, Transportation Research Board, Washington, D.C.
Emmerson, J. (1969). “Speeds of cars on sharp horizontal curves.” Traffic Eng. Control, 11(3), 135–137.
Fitzpatrick, K., et al. (2000). Design factors that affect driver speed on suburban arterials, Texas Transportation Institute, College Station, Tex.
Moyer, R. A., and Berry, D. S. (1940). “Marking highway curves with safe speed indications.” Proc. HRB, Vol. 20, Highway Research Board, Washington, D.C., 399–428.
Mudry, M. J. (1999). “Re-examining the design of low-speed urban curves.” Enhancing Transportation Safety in the 21st Century ITE Int. Conf., Institute of Transportation Engineers, Kissimmee, Fla., 7–13.
Information & Authors
Information
Published In
Journal of Transportation Engineering
Volume 131 • Issue 2 • February 2005
Pages: 112 - 119
Copyright
© 2005 ASCE.
History
Received: Jun 11, 2003
Accepted: Feb 5, 2004
Published online: Feb 1, 2005
Published in print: Feb 2005
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