No more helmet hair: Hovding's "invisible" helmet is an air bag tucked away in a collar that gets fastened around a cyclist's neck. It's aimed at urban cyclists and priced at $535. Courtesy of Hovding hide caption

itoggle caption Courtesy of Hovding

Electric bikes made by French company Moustache are displayed during the Cycle Show 2013 in Paris last month. Charles Platiau/Reuters /Landov hide caption

itoggle caption Charles Platiau/Reuters /Landov

A mechanic repairs a bike at Calmera bike shop in Madrid in September. As car sales slump across Europe, bicycle sales in Spain are outpacing cars — a trend seen across much of the Continent. Pablo Blazquez Dominguez/Getty Images hide caption

itoggle caption Pablo Blazquez Dominguez/Getty Images

"So I got a ticket," bike commuter Molly Millar wrote in a tweet last week. The Vancouver cyclist had left her bike in a rack outside her office building. Molly Millar/Twitter hide caption

itoggle caption Molly Millar/Twitter

In a photo taken on July 24, ELF bike owner Mark Stewart discusses the unusual vehicle during his trip from North Carolina to Massachusetts. Valerie Bonk/AP hide caption

itoggle caption Valerie Bonk/AP

Supreme Court Justice Stephen Breyer fell from his bike while riding along the National Mall in Washington, D.C., on Friday. He underwent surgery for a fractured shoulder on Saturday. Alex Brandon/AP hide caption

itoggle caption Alex Brandon/AP

A bicycle built by British firm Donhou was created with the goal of hitting high speeds,€” perhaps including 100 mph. Oli Woodman/Bike Radar hide caption

itoggle caption Oli Woodman/Bike Radar

The thief who stole Harly and Courtney Forbes' tandem bicycle Monday returned it Wednesday, along with a note of apology. Police say they are still investigating the case. Vancouver Police hide caption

itoggle caption Vancouver Police

Using a cardboard liner allows a cycling helmet to be lighter and stronger than standard models, says designer Anirudha Surabhi. Anirudha Surabhi hide caption

itoggle caption Anirudha Surabhi

Jennifer Drake and her daughter, Alex, pause before their morning ride. "My daughter and I bike to school (her work) 3 miles roundtrip daily," Drake writes. @JennLDrake hide caption

itoggle caption @JennLDrake

Three men stand with their penny farthing bicycles. Follow their example for Bike to Work Day, and take a photo of yourself and your bike. Then, post the photo to Twitter or Instagram, with the hashtag #NPRbike. Hulton Archive/Getty Images hide caption

itoggle caption Hulton Archive/Getty Images

Bartender Matt Carucci says he rarely feels safe biking in the city but often rides without a helmet anyway. "There are a lot of other ways to hurt yourself," he says. John Rose/NPR hide caption

itoggle caption John Rose/NPR

A cyclist uses a fader to manipulate music, on Cogoo's Turntable Rider kit that blends DJ and BMX culture. NPR hide caption

itoggle caption NPR

Michael Gill was 21 when he sold his Peugeot racing bike in 1985.

Michael Gill hide caption

itoggle caption Michael Gill

A cyclist in passes a line of cars during rush hour in Beijing. While auto sales remain strong in China, the country is also reportedly experiencing a resurgence of interest in bicycles.

Andy Wong/AP hide caption

itoggle caption Andy Wong/AP

Pedestrian Dionette Cherney died after a bicycle accident in San Francisco in July. The city has seen more frustration between cyclists and pedestrians this month, as they are forced to share one sidewalk during work on the city's iconic Golden Gate Bridge. Paul Sakuma/AP hide caption

itoggle caption Paul Sakuma/AP