Study Details

Study Title: A Bayesian Analysis of the Effect of Horizontal Curvature on Truck Crashes Using Training and Validation Data Sets

Authors: Schneider et al.

Publication Date:JAN, 2009

Abstract: The research on the effects of roadway geometry on truck crashes is relatively limited in comparison to predictive models developed for total vehicle crashes. The most common predictive models currently used are Poisson and negative binomial models. This study uses a negative binomial model but applies the Full Bayes methods for improving model performance. To successfully use Bayes methods, a learning process was used to develop a final model, which was then compared to a separate validation dataset to verify its accuracy. The data set used for this study is based on rural two-lane collector and arterial horizontal curves in Ohio, comprised of 15,390 observations from crash records between 2002 through 2006. Specific areas of interest within this study include the impact of shoulder width, horizontal curve radius, curve length and other traffic parameters. The final results indicated a significant increase in truck crashes due to both horizontal curvature and passenger vehicle volumes. The final model's predictions were improved compared to the initial model, indicating that the learning process is a viable tool for future crash model development.

Study Citation: Schneider, W.H., K. Zimmerman, D. Van Boxel, and S. Vavilikolanu,"A Bayesian Analysis of the Effect of Horizontal Curvature on Truck Crashes Using Training and Validation Data Sets." TRB 88th Annual Meeting Compendium of Papers CD-ROM. Washington, D.C., (2009).


CMFs Associated With This Study

Category: Alignment

Countermeasure: Increase in horizontal curvature by five degrees

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.29-28.92 StarsTruck relatedAllNot SpecifiedRural

Countermeasure: Increase in horizontal curvature by four degrees

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.23-22.62 StarsTruck relatedAllNot SpecifiedRural

Countermeasure: Increase in horizontal curvature by one degree

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.05-52 StarsTruck relatedAllNot SpecifiedRural

Countermeasure: Increase in horizontal curvature by three degrees

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.16-16.52 StarsTruck relatedAllNot SpecifiedRural

Countermeasure: Increase in horizontal curvature by two degrees

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
1.11-10.72 StarsTruck relatedAllNot SpecifiedRural

Countermeasure: Increase in horizontal curvature from X to Y degrees

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
CMF EquationCRF Equation2 StarsTruck relatedAllNot SpecifiedRural