Conference Interactive Program
To view the 2013 Annual Meeting Interactive Program
TRB 91st Annual Meeting (January 22-26, 2012)
Highway Safety Performance
Jan 24 2012 7:30PM- 9:30PM
Marriott, Salon 2
Developing Crash Modification Factors for Interchange Influence Areas on Urban Four-Lane Freeways Using Multivariate Adaptive Regression Splines (12-2378)
Crash modification factors (CMFs) are used to measure the safety impacts from changes in specific geometric characteristics. Their development has gained much interest following the adoption of CMFs by the recently released Highway Safety Manual (HSM) and SafetyAnalyst tool. This paper aims at developing CMFs for interchange influence areas on urban four-lane freeways in the state of Florida. The need to model freeway interchange areas apart from their basic mainlines has been recognized by SafetyAnalyst. Different methods for developing CMFs can be found in the literature. This paper introduces a promising data mining method known as multivariate adaptive regression splines (MARS) for CMF development. MARS is characterized by its capability to accommodate the nonlinearity in crash predictors, which can be a mixture of continuous and categorical variables. In addition, MARS allows the impact of more than one geometric variable to be simultaneously considered when estimating CMFs. Separate CMFs were developed for inside and outside shoulder widths within the interchange influence areas. The results showed that MARS produced CMFs with higher confidence than those using the negative binomial model. The influential variables identified included the inside shoulder width, outside shoulder width, traffic volume, shoulder type, and speed limit. It was also found that inside shoulders less than 4 ft and 4 to 6 ft experienced safety improvement in relative to the 4-ft width.
Haleem, Kirolos M., Florida International University
Gan, Albert , Florida International University
Lu, Jinyan , Florida International University
Transportation Research Board. 500 Fifth St. NW, Washington, D.C. 20001
Copyright © 2012. National Academy of Sciences. All Rights Reserved.