Relationship of Lane Width to Safety for Urban and Suburban Arterials

• Authored by:  Ingrid B. Potts
• Co-authored by:  D. W. Harwood , K. R. Richard

Potts, I., Harwood, D., and Richard, K. “Relationship of Lane Width to Safety for Urban and Suburban Arterials,” Presented at the 86^th Annual Transportation Research Board meeting, Washington, D.C. (2007).

      The focus of this study was to further the understanding of how lane widths narrower than 12 feet affect the safety performance of roadway segments and intersections.  Because a statistically sufficient sample size was not available, the researchers utilized a cross-sectional safety analysis instead of a before-and-after observational study.  The study included 408 miles of urban and suburban arterials in Minnesota and Michigan.  The results of the study indicated that, in general, lane widths less than 12 feet were not associated with increases in crash frequencies on urban and suburban arterials.  However, inconsistent results were observed in for three specific situations:  lane widths of 10 feet or less on four-lane undivided arterials, lane widths of 10 feet or less on approaches to four-leg STOP controlled intersections, and lane widths of 9 feet or less on four-lane divided arterials.  In these situations, narrow lane widths should be used with caution.