Study Details

Study Title: Developing Lane Width Crash Modification Factors for Urban Multilane Roadways with Curb-and-Gutter and Asymmetric Lanes

Authors: Mbatta et al.

Publication Date:JAN, 2012

Abstract: "This study developed lane width crash modification factors (CMFs) for urban curb-and gutter multilane roadways with asymmetric lanes, i.e., outside lane wider than inside lane. The roadway segments used were urban four-lane with a raised median (4D) and with a two-way left-turn lane (5T). Data used included 25 centerline miles of 5T segments and 39 centerline miles of 4D segments. Three crash categories were evaluated; KABCO { Fatal (K), incapacitating injury (A), non-incapacitating injury (B), possible injury (C) and property damage only crashes (O)}, KABC {Fatal (K), incapacitating injury (A), non-incapacitating injury (B), and possible injury crashes (C)}, and PDO (property damage only) crashes. A cross-sectional method was used as it was the most practical and feasible for this study. Six-year (2004 to 2009) of segment crashes were examined. The analysis involved statistical modeling using the negative binomial model, whose coefficients were used to develop multiplicative CMF equations for a combined effect of variable inside and outside lane width. In summary, the results show that reducing the inside lane width from 12 ft to 11 ft does not affect estimated crash frequency of 4D segments for all three crash categories, and PDO crashes for 5T segments. However, narrowing the inside lane width appears to be associated with increased estimated KABCO and KABC crashes for 5T sections. The results also suggest that widening the outside lane from the baseline 12 ft causes a reduction in estimated crash frequency for all three crash categories (KABCO, KABC, and PDO) for both 4D and 5T segments.

Study Citation: Mbatta, G., T. Sando, and R. Moses, "Developing Lane Width Crash Modification Factors for Urban Multilane Roadways with Curb-and-Gutter and Asymmetric Lanes." TRB 91st Annual Meeting Compendium of Papers. Washington, DC, 2012.

Related Citations: Sando, T. and Moses, R., "Operational and Safety Impacts of Restriping Inside Lanes of Urban Multilane Curbed Roadways to 11 Feet or Less to Create Wider Outside Curb Lanes for Bicyclists," Florida Department of Transportation, Tallahassee, FL (2011).

Study Report: Download the Study Report Document


CMFs Associated With This Study

Category: Roadway

Countermeasure: Convert 12-ft inside and outside lanes to 12-ft inside lane and X-ft outside lane

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
CMF EquationCRF Equation4 StarsAllAllNot SpecifiedUrban
CMF EquationCRF Equation4 StarsAllK,A,B,CNot SpecifiedUrban
CMF EquationCRF Equation4 StarsAllONot SpecifiedUrban

Countermeasure: Convert 12-ft inside and outside lanes to X-ft inside lane and X-ft outside lane

CMF CRF(%)QualityCrash TypeCrash SeverityRoadway TypeArea Type
CMF EquationCRF Equation4 StarsAllONot SpecifiedUrban
CMF EquationCRF Equation4 StarsAllAllNot SpecifiedUrban
CMF EquationCRF Equation4 StarsAllK,A,B,CNot SpecifiedUrban