Yes, protected bike lanes do make streets safer to cycle on. Evidence comes in the form of a new study conducted by the University of Minnesota for the Minnesota Department of Transportation. And advocates can cite it to planners, politicians, transit officials and motorists who object to losing driving or parking space on the roads to cyclists.
Researchers examined driver behavior on Minnesota roadways with different types of bicycle accommodations. “Drivers on roadways with bicycle lanes were less likely to encroach into adjacent lanes, pass, or queue when interacting with cyclists than drivers on roadways with sharrows, signs designating shared lanes, or no bicycle facilities,” the report states.
Drivers were more likely to leave cyclists in peace when the cyclists were in their own lanes. Sharrows and “share the road” or “bike route” signs didn't help significantly. “From the perspective of reducing potential traffic impacts, bicycle lanes are to be preferred over sharrows or signage,” the researchers conclude. And separated lanes work better than ones merely striped.
One study, however, doesn't prove anything. The researchers acknowledge that their observations didn't include any traffic jams or perpetually overcrowded roads and they only looked at nine streets. But the study concludes that it adds “to the body of evidence in the literature that the addition of buffered and striped bicycle lanes to a roadway increases the predictability of driver behavior, increases the likelihood that drivers will remain in their travel lanes, and reduces the risk that may be associated with drivers encroaching into or shifting travel lanes.”
And if they're wide enough, unmarked shoulders can function as bike lanes and protect users, the study adds.
Find the report, Traffic Impacts of Bicycle Facilities, at http://dot.state.mn.us/research/reports/2017/201723.pdf