Researchers at the University of Minnesota strapped radar to their handlebars and hit the roads of Hennepin County to see how much space drivers were willing to give cyclists.

What they discovered may shock half of you.

Working with the county, researchers plotted half-mile routes along half a dozen city and county roads, some with bike lanes, some without.

Then the grad students rolled.

Up and down the roads they pedaled in congested afternoon rush-hour traffic, while their equipment recorded every car, truck and bus that passed — and how closely they passed.

Minnesota state law requires drivers to give cyclists a wide berth, at least 3 feet, when passing. Most drivers do.

During the road test, nearly 3,000 drivers passed the three researchers on bikes. When the team at the U’s Humphrey School of Public Affairs analyzed the radar data, they found just 33 drivers had broken the law and crowded in uncomfortably close to the cyclists.

What shocked researchers and county transit planners was the target of most of these drive-bys.

Lila Singer-Berk was one of three graduate students who did the legwork on the 2017 study. She was the only woman in the group.

Twenty-four of the 33 incidents of driver encroachment happened to her.

The radar recorded one driver who blew by just 13 inches from her — so close, she could have elbowed the vehicle in passing.

“It feels closer,” said Singer-Berk, who now works as a transportation analyst. “It’s really alarming.”

After Prof. Greg Lindsey shared the study results last week, he started hearing from women with their own stories of close calls, catcalls and hands that reached out of car windows to slap their rear ends as they biked by.

This would be a nice day for a bike ride.

The flowers are blooming, the heat index is well below triple digits and we live in some of the nation’s bike-friendliest cities. Minnesotans hop on a bike an estimated 75 million to 96 million times a year.

But if you look around, you’ll see that a lot of the people on bikes seem to be men.

The cycling gender gap was on Hennepin County planners’ minds as they teamed up with the university to study how drivers and cyclists behave around each other. Women are more likely than men to cite safety as a concern with biking, Lindsey noted, and the prospect of being crowded or slapped on the butt doesn’t make the exercise more appealing.

Hennepin County wants more people on bikes. It’s good exercise, it’s great fun, and it cuts down on pollution and gridlock.

The county has 259 miles of on-street bikeways and another 500 miles of bike trails and is adding more.

So the county was hoping to study how all that new bike infrastructure affected cyclist safety. It wasn’t expecting to learn that women were four times more likely to get crowded on their bike commute.

“We wanted to find out, as we were building our bike network, how different types of bike infrastructure is having an effect on people’s bike safety,” said Laura Fredrick of the county’s Healthy Community Planning, who teamed up on the study. “What we found was that female cyclists had a significantly different experience riding than the male riders did. … Female riders tend to have more aggressive interactions with drivers than male riders did.”

The study was supposed to be a test of the bike infrastructure. It was a test 33 drivers failed.

The streets selected for the study ranged from the buffered downtown bike lanes that lift cyclists out of traffic on Washington Avenue, to the bollard-marked bike lanes along Minnetonka Avenue in St. Louis Park, to streets with no bike infrastructure at all, like the congested meat grinder that is NE. Broadway.

When they analyzed the readings, researchers found — no surprise — that protected bike lanes offered the best protection. Cars stayed an average 7.5 feet from cyclists cruising along a bike lane separated from traffic by bollards. No bike lanes, more close calls. About 5% of the cars that passed the cyclists on four-lane Broadway came closer than 3 feet.

This study didn’t — and couldn’t — explore what was going on in the heads of the drivers who buzzed graduate students Singer-Berk, Isaac Evans and Joshua Pansch.

Maybe they were in a rush, maybe they were in a bad mood, maybe they had their noses buried in a phone and didn’t realize they came within 13 inches of squashing someone into the asphalt. The students followed the same path for each trip, carefully measured from the curb, and avoided intersections where traffic can bunch up at red lights.

The only variable that changed was each driver’s regard for the laws of physics and the value of human life.

For more information about cycling, safety and bike routes in Hennepin County, visit: hennepin.us/residents/transportation/ride-hennepin.

You can read about road hogs and sexist pigs here: genderpolicyreport.umn.edu/bicycles-gender-and-risk.