Bicyclists will take it all off - well, maybe half off - on a Shanghai ride for World Car-Free Day. They want to call attention to healthy living.

Cyclists, both Chinese and expat, take a clothingoptional bike ride along downtown Shanghai to promote a low-carbon lifestyle. This year the World Car-Free Day falls next Thursday.

Bicyclist and environmentalist Zhang Linyuan plans to strip down to swimming trunks and shoes and lead a "clothing optional" ride in Shanghai on Saturday to promote biking for the World Car-Free Day.

The variously called "the naked, half-naked and clothing-optional" ride will take place after a fully clothed event in which 37-year-old Zhang leads bicyclists on an official ride to mark the day and the importance of reducing the number of polluting cars.

The World Car-Free Day officially falls next Thursday, but activities to convey the message will take place in Shanghai this weekend.

The stripped-down bike route has not been announced and interested people will just have to tag along after the official bike ride and see what unfolds.

Zhang, founder of Prodigy Mountain Bike Club that organizes this biking event, suggests they gather at 11am on Longteng Ave, dubbed as "Shanghai's Little Bund," in Xuhui District.

"Of course, we will not hide ourselves in the dark. Instead, we will take to busy roads because after all, the event is to promote biking and a low-carbon and eco-lifestyle," Zhang tells Shanghai Daily.

Speaking of the absence of shirt and trousers, he says, "It doesn't involve anything bad at all, as you can see from our photos taken on last year's ride, which was healthy and sunny." Girls wore bikinis.

Zhang says he wants to keep it to 30 to 50 cyclists. He has also been contacted by other bike clubs, extreme sports clubs and expects to see skateboards, roller skates, in-line skates and parkour participants.

Clothing-optional bike rides are very common abroad, but considering the regulations in China, Zhang doesn't want the ride to be so showy and conspicuous that authorities get involved with what they might call a public nuisance.

His worries are understandable, since a similar event in Guangzhou, capital city of Guangdong Province, earlier in the year was canceled at last minute due to pressure from authorities.

On June 19, a biker posted an online call for a "fully naked bike ride" in the Guangzhou university town. It got thousands of hits and dozens of cyclists said they wanted to take part. A few days later, the organizer posted a change - now it would be a "half-naked bike ride." He later canceled it, citing "personal reasons."

Nonetheless, on the appointed day, a handful of bicycles in beach costumes showed up; they soon dispersed since they felt rather isolated.

The organizer, who canceled at the last minute, later told media, "I didn't expect so many participants to apply, to get attention from everywhere, and the event was never sent for approval, hence never approved by authorities."

Similarly, the upcoming clothing-optional bike ride, organized by Zhang's biking club, was never submitted for approval.

"There is no way that it will be approved, hence no reason to apply," Zhang explains, saying that he informed relevant public security and traffic departments and was warned "not to make the event too big."

He doesn't want more than 50 participants, "so we don't attract too much attention. You can't kick people out if they come, right?" he asks.

Unlike the unprepared organizer in Guangzhou, Zhang has experience from a similar event in Shanghai last August, called the "Sun Ride." On a hot day, around 30 cyclists - 20 men and 10 women - took on a one-and-half-hour ride on busy roads from Shanghai Stadium to the Bund. More than half were expats, and everyone was required to dress for the beach.

Zheng Yun, a 35-year-old mobile designer, was one of the 10 women on the Sun Ride last summer. She wore a bikini and thought it was suitable.

"You wear a bikini on the beach anyway, it wasn't so different. It's quite healthy and great for promoting the sport," she recalls. She plans to join the ride this year, again wearing a bikini. "After all, we need to follow the regulations," she says.

In last year's Sun Ride, Zheng and the others turned a lot of heads. Cars slowed down, people took photos of the easy riders, but there were no traffic jams since they rode quickly and smoothly and no one was naked.

"It was fairly successfully, so we plan to do it again this year. And this year, we will not regulate clothing, making it a real clothing-optional ride," says Zhang.

He hasn't decided whether to bare it all.

"I would love to, but since I'm the organizer, I need to take a lot into consideration," he admits.

Zhang is surely familiar with the national Administrative Penalties for Public Security. One could be arrested (or just sent home) for violating the second item of Article 19: "Disturbing the public order of stations, wharves, civil airports, markets, bazaars, parks, theaters, entertainment centers, sports grounds, exhibition halls or other public places."

If anyone shows up without clothes, police are likely to suggest they cover up. If a crowd gathers and the person doesn't cover up, he could be detained.

"I'm not sure, but since we haven't put any limits this time, some people might come naked, and I guess they'll just put on clothes if the cops come, or we can change our route on the way," Zhang notes.

He says there will be regular bikes, mountain bikes, tricycles, unicycles, decorated bikes and other kids of one, two or three-wheel transport for one person.

Zhang has already received a lot of responses, but there's no need to apply. Interested bikers should show up at the spot on the appointed day.