Crash Comparison of Single Point and Tight Diamond Interchanges
Publication: Journal of Transportation Engineering
Volume 131, Issue 5
Abstract
Although the single point interchange (SPI) has been around for approximately , very few attempts have been made to evaluate its safety performance with a similar configuration, the tight diamond interchange (TDI). This paper provides a crash comparison between the TDI and the SPI interchanges for intersection related crashes on the cross road only. The SPIs considered in this study are without frontage roads. Data from 27 diamond interchanges (DIs) in Washington were used in building a negative binomial model to predict total crashes and injury/fatality based on the off-ramp flow, cross-road flow, and separation distance between left and right ramp terminals. Crash analysis of 13 SPI sites was used to compare with newly developed crash models of diamond interchanges. Wilcoxon signed-rank test was applied for safety comparisons between the SPI and TDI. The safety comparison did not reveal a significant difference between the two types of interchanges neither for total crash. However, the single point urban interchanges were found to be safer than the comparable DIs for injury/fatality frequencies.
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Acknowledgments
The writers recognize the cooperation of five states: Maryland, California, Virginia, Missouri, and Washington that have provided them with supplemental data of crash frequencies diagrams of sites, and AADTs on cross roads and off ramps.
References
Garber, N. J., and Smith, M. J. (1996). “Comparison of the operational and safety characteristics of the single point urban and diamond interchanges.” VTRC 97-R6, Virginia Transportation Research Center, Va.
Selinger, M. J., and Sharp, W. H. (2000). “Comparison of SPUI and TUDI interchange alternatives with computer simulation modeling.” Proc., ITE 2000 Annual Meeting and Exhibit, Nashville, Tenn.
Walpole, R. E., and Myers, R. H. (1978). “Nonparametric statistics.” Probability and statistics for engineers and scientists, Macmillan, New York, 484–485.
Information & Authors
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Published In
Journal of Transportation Engineering
Volume 131 • Issue 5 • May 2005
Pages: 379 - 381
Copyright
© 2005 ASCE.
History
Received: Mar 5, 2004
Accepted: Jul 21, 2004
Published online: May 1, 2005
Published in print: May 2005
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