Minnesota state law requires motorists to give 3 or more feet of clearance when passing a bicyclist, and the good news is a large majority of drivers obey.

The bad news is there are still too many drivers who don’t allow enough space when overtaking bicyclists, and that sets up potentially risky interactions between those traveling on two wheels and those on four.

Crashes involving motor vehicles and bicyclists topped 800 in 2017, according to figures from the Minnesota Department of Public Safety. Those mishaps resulted in 738 injured bicyclists and six deaths. About a quarter of the bicyclists hit were cycling in the same direction as traffic before the crash.

Bicyclists are subject to the same traffic laws as motor vehicle operators, and granted, they don’t always follow them. But as cities and counties push to make bicycling an attractive alternative form of transportation, the challenge is to install infrastructure to keep cyclists feeling safe and comfortable without disrupting traffic flow.

What kinds of bike lanes work best? Those separated from traffic? Those blocked off by posts? Those simply painted on the roadway?

In collaboration with Hennepin County, University of Minnesota graduate students looked at how much room drivers allow when passing bicyclists and how often they pass within fewer than 3 feet. Researchers found that the type of bicycle lane dictated how much space motorists gave.

The students strapped on bike-mounted radars and a GoPro camera to capture more than 2,900 vehicle passing events on urban routes to determine the vehicular encroachment rate and passing distance. The results published in the May edition of the ITE Journal found the largest passing distance and fewest encroachments occurred on routes with protected bike lanes, such as the bicycle track on Washington Avenue and bike lanes separated from traffic by bollards or medians on Plymouth Avenue N.

Bike boulevards, streets like Bryant Avenue S. in Minneapolis, which have been optimized for bicycles with traffic calming elements such as speed humps, curb extensions and medians, had some of the highest encroachment rates. Since parking is allowed on both sides of bike boulevards, they essentially turn into one-lane roads, and encroachment can easily occur since vehicles travel in both directions, the study found.

But encroachments occurred most on four-lane roads with no bike lanes, such as on Broadway Street NE., where 5.7 percent of motorists did not leave an adequate passing buffer. That could be largely due to the presence of vehicles in adjacent lanes.

While encroachment rates were fairly low, bicyclists are put in danger too often. Say 1,000 bicyclists a day pedal along Broadway; that’s 57 times a day a cyclist could experience a close brush, or something worse, with a vehicle.

The study confirms that road design and traffic planning decisions affect how vehicles and cyclists interact, said Greg Lindsey, professor at the Humphrey School of Public Affairs. He said the study can help planners installing bike lanes determine the right type of design for the road and whether it’s worth the investment to reduce encroachments.

“Hennepin County is to be commended for acquiring evidence to make informed decisions,” Lindsey said. The information “can help us know if our investments are prudent and going in the right direction.”


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