Last year, cities built 40 of the so-called green lanes, according to the Bikes Belong Foundation's Green Lane Project, an organization working with six cities — Austin; Chicago; Memphis; Portland, Ore.; San Francisco and Washington — to add them.
That may not seem like a large number. But between 1874 and 2011, just 62 protected lane projects were build nationwide, the group says.
Protected lanes are different from traditional bike lanes that separate cyclists from motorists with just a stripe of paint. The protected lanes add a barrier, such as a curb, parked cars or plastic posts, between moving cars and bicycle traffic to make cyclists feel safer.
A big factor in their growing popularity: Recent studies show that the lanes can spur economic activity.
A study last year by the New York City Department of Transportation found that small businesses near protected bike lanes installed in 2007 saw sales grow much more sharply than the borough average. Another study by Portland State University found that people in Portland who drove to local businesses spent more money per visit than bicyclists, but cyclists visited the same businesses more often and spent more overall.
Young people, whose driving habits are shifting, also are a factor in the emergence of more green lanes.
A study by the Frontier Group think tank last year found that annual miles traveled by car among 16- to 34-year-olds dropped 23% from 2001 to 2009. It also found that people in that age group took 24% more bike trips in the same period. A 2011 study by researchers at the University of Michigan Transportation Research Institute found that the percentage of young drivers with licenses is declining.
The young people help comprise a group that economic forecaster Richard Florida has dubbed the "creative class," which would rather spend their money on high-end smartphones, gadgets and bicycles.
That's a class that many cities are working hard to attract, and green lanes can help.
Chicago Mayor Rahm Emanuel, who ran for office in 2011 on a platform of luring new tech and creative businesses to the city, pledged to build 100 miles of protected bike lanes by the end of his first term.
"They're an integral part of my economic development strategy," Emanuel says. "It's no coincidence that the first protected bike lanes were on Kinzie Street, and that's exactly where Google-Motorola Mobility is putting their headquarters with 2,800 jobs."
The city recently unveiled its Chicago Streets for Cycling plan, which aims to have 650 miles of green and traditional bike lanes in the city by 2020, which would give it more green lanes than any other city in the country and would put a bike lane of some type within a half-mile of every Chicagoan.
Other cities — including Atlanta, Salt Lake City, Indianapolis, St. Louis, Kansas City, Mo., Lincoln, Neb., and Wichita — are adding or planning to add green lanes, says Martha Roskowski, director of the Boulder, Colo.-based Green Lane Project.
"The leaders in these cities are saying, 'We get it. If we want to be a competitive, vibrant city, we need to make our streets work better,' " Roskowski says.
In Atlanta, four protected bike lane projects are in development or planned, says Rebecca Serna, executive director of the Atlanta Bicycle Coalition.
"The thing we really like about protected bike lanes is they really get the people who are interested in cycling but are concerned about their safety," she says.
Interest in the lanes has grown in the past two years, Serna says. And young people are a driving force.
"Atlanta really is a university town," she says. "I think a lot of cities have found that bike infrastructure helps you keep your highly educated young people in the city after they graduate."