Narrowing travel lanes is associated with significantly lower numbers of non-intersection traffic crashes within speeds of 30 to 35 mph, according to a new study.

A National Investigation on the Impacts of Lane Width on Traffic Safety: Narrowing Travel Lanes as an Opportunity to Promote Biking and Pedestrian Facilities Within the Existing Roadway Infrastructure by the Johns Hopkins Bloomberg School of Health included analysis of more than 1,000 street sections across seven cities. Researchers also interviewed officials at five state Departments of Transportation.

The most immediate candidates for lane width reduction projects may be urban streets of 11 to 13 feet within the 20 to 35 mph range that don’t serve transit or freight, according to the 129-page study.

“Narrowing travel lanes is the easiest and most cost-effective way to accommodate better sidewalk and bike lane facilities within the existing roadway infrastructure,” the authors noted. However, reducing lane widths is likely to have limited benefit if other street design changes are ignored so the study promotes context-sensitive design in general.

The analysis includes some caveats: Nine- and 10-foot lanes may not be the best width for freight or bus corridors and only two cities in the study experience snowy winters (Denver and Salt Lake City).

The full report is available here.