Appropriate Regression Model Types for Intersections in SafetyAnalyst
Publication: Journal of Transportation Engineering
Volume 138, Issue 10
Abstract
Highway agencies in the United States have started implementing SafetyAnalyst, highway safety management software. Some agencies have been developing or considering developing safety performance functions (SPFs) using local data to maximize the benefits of the software. With multiple years of data on hand, several models are available for developing the SPFs, yet there is no reliable guide to selecting appropriate models. To this end, this study examined 11 models, including 8 panel and 3 cross-sectional models, to recommend appropriate model types for intersection SPFs of SafetyAnalyst. Data collected from 18,356 intersections in Virginia over the period 2003–2008 were used. A cross-sectional model with summed or averaged crash frequencies was found to severely underestimate a dispersion parameter that plays a critical role in the empirical Bayes method. Panel models with independent correlation and autoregressive Order 1 correlation and a pooled cross-sectional model were found to be appropriate across all 8 subtypes. Agencies unable to construct panel data and develop panel models can apply the pooled cross-sectional model, which does not require matching the same intersections across different years.
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Acknowledgments
The authors thank Linda Evans of the Virginia Center for Transportation Innovation and Research for her great editorial help and the Virginia Department of Transportation for sponsoring the study.
References
AASHTO. (2011). “SafetyAnalyst overview.” Washington, DC, 〈www.safetyanalyst.org.〉 (Jul. 28, 2011).
Akaike, H. (1974). “A new look at the statistical model identification.” IEEE Trans. Autom. Control, 19(6), 716–723.
Anastasopoulos, P. C., and Mannering., F. L. (2009). “A note on modeling vehicle accident frequencies with random-parameters count models.” Accid. Anal. Prev., 41(1), 153–159.
Cameron, A. C., and Trivedi., P. K. (1998). “Regression Analysis of Count Data.” Econometric Society Monograph, No. 30, Cambridge University Press, New York.
Federal Highway Administration (FHwA). (2009). SPF development guides: Developing SPFs with state or local highway agency data, U.S. DOT, Washington, DC, 〈http://www.safetyanalyst.org/spf_dev_guidelines/Developing%20SPFs%20with%20State%20or%20Local%20Highway%20Agency%20Data.pdf〉 (Jul. 28, 2011).
Fridstrom, L., Ifver, J., Ingebrigtsen, S., Kulmala, R., and Thomsen, L. K. (1995). “Measuring the contribution of randomness, exposure, weather, and daylight to the variation in road accident counts.” Accid. Anal. Prev., 27(1), 1–20.
Gardiner, J. C., Luo, Z., and Roman, L. A. (2009). “Fixed effects, random effects, and GEE: What are the differences?” Statist. Med., 28, 221–239.
Harwood, D. W., Torbic, D. J., Richard, K. R., and Meyer, M. M. (2010). “Safetyanalyst: software tools for safety management of specific highway sites.”, Midwest Research Institute, Kansas City, MO.
Hu, F. B., Goldberg, J., Hedeker, D., Flay, B. R., and Pentz, M. A. (1998). “Comparison of population-averaged and subject-specific approaches for analyzing repeated binary outcomes.” Am. J. Epidemiol., 147(7), 694–703.
ITT Corp. (2009). “SafetyAnalyst user’s manual.”, U.S. DOT, Washington, DC.
Kweon, Y.-J., and Lim, I.-K (2010). “Appropriate regression model types for the empirical bayes method and safetyanalyst.” Proc., 89th Annual Meeting of the Transportation Research Board, Transportation Research Board, Washington, DC.
Liang, K.-Y., and Zeger, S. (1986). “Longitudinal data analysis using generalized linear models.” Biometrika, 73(1), 13–22.
McCullagh, P., and Nelder, J. A. (1989). Generalized linear models, Chapman and Hall, London.
Pan, W. (2001). “Akaike’s information criterion in generalized estimating equations.” Biometrics, 57(1), 120–125.
Raftery, A. E. (1995). “Bayesian model selection in social research.” Sociol. Methodol., 25, 111–163.
SAS Institute Inc. (2004). “The GENMOD procedure.” Chapter 31, SAS/STAT 9.1 user’s guide, Cary, NC.
Virginia DOT. (2011). “About VDOT: Virginia’s highway system.” 〈www.virginiadot.org/about/vdot_hgwy_sys.asp.〉 (Jul. 28, 2011).
Information & Authors
Information
Published In
Journal of Transportation Engineering
Volume 138 • Issue 10 • October 2012
Pages: 1250 - 1258
Copyright
© 2012 American Society of Civil Engineers.
History
Received: Aug 3, 2011
Accepted: Mar 30, 2012
Published online: Apr 2, 2012
Published in print: Oct 1, 2012
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