Cities are increasingly changing bike lanes to make them safer in light of fatal crashes involving cyclists and cars.
From Boston to San Francisco and New York to Tokyo, traditional bike lanes running alongside vehicle traffic are being replaced in favour of "protected" lanes or "cycletracks," where physical barriers like concrete curbs, planters or fences separate cyclists from vehicle traffic.
"For 50 years, we've just been putting down a stripe of white paint, and that was how you accommodated bikes on busy streets," says Martha Roskowski, director of People for Bikes, a Boulder, Colorado-based advocacy group that's calling for better designed bike lanes. "What we've learned is that simply doesn't work for most."
Here's a rundown of how bike lanes are evolving:
Where it's happening
Protected lanes have been sprouting up in the U.S. since at least 2007, when New York started rolling them out on a wide scale.
Today, there are roughly 240 miles of lanes in 94 cities, according to People for Bikes. That's an increase from about 100 miles of lanes in 32 cities in 2013, though still a tiny fraction of all bike lanes, Roskowski says.
This year alone, at least two dozen cities have so far installed new types of lanes, the organisation says.
In Chicago, Mayor Rahm Emanuel has promised to build 50 miles of the lanes over the next three years on top of 9 miles this year.
And in Boston, where eight cyclists died earlier this year, a short stretch of Beacon Street leading to the Fenway Park area has been reconfigured.
Rows of parked cars now serve as a buffer to cyclists, and there are plans to extend that path and incorporate the design on other major arteries.
Not created equal
Designs for protected lanes vary by city, and not all have been warmly received.
Along a short part of San Francisco's famous Market Street, pavement nearest the curb was recently built up higher than vehicle lanes to create a distinct path for bikes.
But Chris Cassidy, of the San Francisco Bicycle Coalition, says the city's first test of a "raised" bike lane still leaves something to be desired because vehicles are still parking in the lane.
In Washington, D.C., the bike lane along Pennsylvania Avenue between the Capitol and White House has proved popular since it was installed in 2010. But some cycling advocates grumble its design " located at the centre of the broad thoroughfare " is impractical and unsafe.
Greg Billing, head of the Washington Area Bicyclist Association, says the centre lane design won't be repeated as the lane is extended past the White House. New rubber barriers were also installed last year to discourage cars from making risky and illegal U-turns through the bike lane.
Among the most bitter bike lane disputes is the ongoing, five-year legal battle waged by wealthy and powerful residents in Brooklyn, New York.
Construction of a parked-car-protected bike path along Prospect Park required elimination of one vehicle lane in 2010.
Norman Steisel, a former deputy mayor, says he and other Park Slope residents simply dispute the traffic and safety data on which the city based its final decision. "You've got to be somewhat respectful for how you get these things done," he says.
In downtown Philadelphia, some two-lane roads are slated to lose a vehicle travel lane to accommodate new protected bike lanes.
But Jonathan Broh, president of the city's Washington Square West Civic Association, says he worries that stores will have a harder time receiving deliveries and that school bus and taxi pickups will snarl traffic.
Europe more advanced
Protected bike lanes aren't a novel idea in Copenhagen, Denmark; Amsterdam; and other European cities where they've been around for decades.
But even cities with less of a biking tradition are embracing the lanes.
London notably opened a number of "cycle superhighways" meant to eventually crisscross the city. Cyclists on these routes are separated from vehicle traffic at crucial segments by a curb.
The city has also seen lofty proposals for elevated bike highways spanning the Thames River or running above railway lines, as well as underground bike paths utilising old subway tunnels.
Asia and beyond
Tokyo and other Japanese cities have long had a strong cycling culture, but some of their protected lanes are placed directly on sidewalks.
That presents challenges as cyclists and pedestrians sometimes compete for the same space, says Mikael Colville-Andersen, CEO of Copenhagenize Design Co., a Danish firm that works with cities on bike infrastructure projects.
Two of China's largest cities, Guangzhou and Shanghai, are also investing heavily in protected lanes and other bike infrastructure, experts say, and India has made progress in improving its lanes.
In South America, the Argentinean capital of Buenos Aires has built nearly 90 miles of bike lanes, many of them protected, in just three years.
"Cities are becoming more rational again, after the folly of car-centric planning," Colville-Andersen says.