Bike lanes along First St., N.E., in Washington, D.C. (Evy Mages/FOR THE WASHINGTON POST)

NO ISSUE polarizes D.C. residents and suburban commuters quite like bicyclists during rush hour. Bike lanes hit the District years ago, and a Montgomery County plan to scale up the region’s bike network is next in line to cause a fuss. Planners should make sure the many benefits of bike lanes do not come at too high a cost for the county’s drivers.

The District counts itself as one of the country’s most bike-friendly cities, and its expansive bike network seems to have gotten people out of their cars and onto two wheels. Bicycle commuting grew by a whopping 290 percent from 2000 to 2013, while automobile traffic volume has stayed steady — even with more people commuting into the District every day. Alexandria and Arlington have experienced similar results.

Taken together, these facts suggest that bike lanes may have prevented an increase in traffic and carbon emissions. And as young people search for new places to work and live, a bikeable environment is appealing. It’s a big payoff for a small price: Compared with other transit projects, putting new markings on pavement and even building the occasional bridge costs little, and the environmental and economic gains seem great.

Montgomery County seeks to bring these same advantages into its own territory with a project for which the local government has earmarked $170 million in its six-year capital budget. Right now, the county is home to long stretches of bike path such as the Capital Crescent and Bethesda Trolley trails. But safe places for biking are separated by big roads with high-volume, high-speed traffic. The county’s planning committee aims to build connecting bike lanes on these roads, along with other cycling thoroughfares that will facilitate both long commutes to work and short rides for errands.

Of course, more often than not the roads where bicycling is most difficult are the same roads that carry the most traffic. Critics of the project fear that adding bike lanes at the expense of lanes for cars or buses could clog an already-congested area. It’s a valid concern, but there are ways for Montgomery to ease the conflict. Where there is room, the county can narrow existing lanes to make way for bicyclists on the side of the roadway. It can also put bike lanes on quieter streets that run parallel to busy corridors. And planners can remove car lanes primarily on roads that have excess traffic capacity.

If implemented poorly, Montgomery County’s plan might prove more of a burden to drivers than a boon to bikers — while raising polarization to Congress-like levels. If done well, the project could do more than make life easier for cyclists: It could ease traffic, cut carbon emissions, and spur economic growth by drawing residents and visitors to newly accessible areas.