00966623

Component

https://doi.org/10.3141/1840-04

http://scholar.google.com...Lord&publication_year=2003

Statistical relationships between traffic crashes and traffic flows at roadway intersections have been extensively modeled and evaluated in recent years. The underlying assumptions adopted in the popular models for intersections are challenged. First, the assumption that the dispersion parameter is a fixed parameter across sites and time periods is challenged. Second, the mathematical limitations of some functional forms used in these models, particularly their properties at the boundaries, are examined. It is also demonstrated that, for a given data set, a large number of plausible functional forms with almost the same overall statistical goodness of fit (GOF) is possible, and an alternative class of logical formulations that may enable a richer interpretation of the data is introduced. A comparison of site estimates from the empirical Bayes and full Bayes methods is also presented. All discussions and comparisons are illustrated with a set of data collected for an urban four-legged signalized intersection in Toronto, Ontario, Canada, from 1990 to 1995. In discussing functional forms, the need for some goodness-of-logic measures, in addition to the GOF measure, is emphasized and demonstrated. Finally, analysts are advised to be mindful of the underlying assumptions adopted in the popular models, especially the assumption that the dispersion parameter is a fixed parameter, and the limitations of the functional forms used. Promising directions in which this study may be extended are also discussed.

This paper appears in Transportation Research Record No. 1840, Statistical Methods and Modeling and Safety Data, Analysis, and Evaluation.

English

p. 31-40

2003

Transportation Research Record

0309085810

Figures (6) ; References (24) ; Tables (1)

Dispersion (Statistics); Functions (Mathematics); Goodness of fit; Mathematical models; Sets; Signalized intersections; Traffic crashes; Traffic flow

Empirical Bayes method; Full Bayes method; Functional forms; Goodness of logic

Toronto (Canada)

Highways; Safety and Human Factors; I81: Accident Statistics

TRIS, TRB, ATRI

Dec 16 2003 12:00AM

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