title: Development of crash modification factors for changing lane width on roadway segments using generalized nonlinear models.
abstract: This study evaluates the effectiveness of changing lane width in reducing crashes on roadway segments. To consider nonlinear relationships between crash rate and lane width, the study develops generalized nonlinear models (GNMs) using 3-years crash records and road geometry data collected for all roadway segments in Florida. The study also estimates various crash modification factors (CMFs) for different ranges of lane width based on the results of the GNMs. It was found that the crash rate was highest for 12-ft lane and lower for the lane width less than or greater than 12ft. GNMs can extrapolate this nonlinear continuous effect of lane width and estimate the CMFs for any lane width, not only selected lane widths, unlike generalized linear models (GLMs) with categorical variables. The CMFs estimated using GNMs reflect that crashes are less likely to occur for narrower lanes if the lane width is less than 12ft whereas crashes are less likely to occur for wider lanes if the lane width is greater than 12ft. However, these effects varied with the posted speed limits as the effect of interaction between lane width and speed limit was significant. The estimated CMFs show that crashes are less likely to occur for lane widths less than 12ft than the lane widths greater than 12ft if the speed limit is higher than or equal to 40mph. It was also found from the CMFs that crashes at higher severity levels (KABC and KAB) are less likely to occur for lane widths greater or less than 12ft compared to 12-ft lane. The study demonstrates that the CMFs estimated using GNMs clearly reflect variations in crashes with lane width, which cannot be captured by the CMFs estimated using GLMs. Thus, it is recommended that if the relationship between crash rate and lane width is nonlinear, the CMFs are estimated using GNMs.
authors.affiliation: Department of Civil and Environmental Engineering, University of Windsor, ON N9B 3P4, Canada. Electronic address: cclee@uwindsor.ca.
authors.forename: Chris
authors.initials: C
authors.lastname: Lee
authors.affiliation: Department of Civil, Environmental and Construction Engineering, University of Central Florida, Orlando, FL 32816-2450, USA. Electronic address: m.aty@ucf.edu.
authors.forename: Mohamed
authors.initials: M
authors.lastname: Abdel-Aty
authors.affiliation: Department of Civil, Environmental and Construction Engineering, University of Central Florida, Orlando, FL 32816-2450, USA. Electronic address: jypark@knights.ucf.edu.
authors.forename: Juneyoung
authors.initials: J
authors.lastname: Park
authors.affiliation: Department of Civil, Environmental and Construction Engineering, University of Central Florida, Orlando, FL 32816-2450, USA. Electronic address: jwang@knights.ucf.edu.
authors.forename: Jung-Han
authors.initials: JH
authors.lastname: Wang
mesh_terms: D000054:Acceleration / Q000009:adverse effects; D000063:Accidents, Traffic / Q000517:prevention & control* / Q000706:statistics & numerical data; D003430:Cross-Sectional Studies; D004215:Distance Perception; D004779:Environment Design; D005431:Florida; D006801:Humans; D017711:Nonlinear Dynamics; D009949:Orientation; D012449:Safety; D013223:Statistics as Topic
keywords: Crash modification factor; Generalized nonlinear model; Lane width; Roadway segment; Speed limit