BOGOTÁ—It’s a misty Sunday morning and the Septima, a choking six-lane thoroughfare usually packed with smoky buses, cars, and yellow taxis, is quiet. There is movement here, but with half the road closed to motorized traffic, hardly any cars.

Instead, parents jog along with running buggies. Cyclists decked out in Lycra take to the street alongside toddlers on tricycles. One couple flies past on a tandem with a baby on the back; behind is a grandmother getting a gentle push up the incline as her pedaling slows. There are men and women, young and old, the Sunday strollers and the athletes. All of Bogotá is here, and it’s marvelous.

This road is one of the cycle superhighways that make up the Ciclovía program in the Colombian capital, the largest street cycle scheme of its kind anywhere in the world.

Started 40 years ago by a small group of activists with “one lorry and a few signs,” today the program is run by the city and sees some 120 kilometres of tarmac turned into a cycle lane from 7 a.m. to 2 p.m. every Sunday and holiday.

In a city often choked by pollution, such a scheme was once revolutionary. Now, it has become one of the city’s most famous exports–hundreds of cities have tried to recreate Ciclovía on their own streets.

For children that tend to live in small apartments, it’s liberating. For families, it is often one of the very best things about living in Bogotá. And kids start very young.

My three-year-old has grown up on this weekly tradition; at first, we took her in the buggy, then behind me in a child’s bike seat. Today she powers along on her scooter, occasionally oblivious to the need to go in a straight line, but perfectly safe from cars even as she zooms along what is normally one of the busiest roads in the sector. When she sees a bike lane now, anywhere, she shrieks: “Look Mummy, it’s ciclovía!”

Cristina Millan, who cycles with her young daughter Ana-Cristina in a trailer, says the Sunday cycling outing has become “part of our life” and her daughter now wants to learn to ride her own bike. Another parent, Juan Carlos Macias, says that after raising his five-year-old son Sebastian in the countryside “where there was no danger, everyone knew him,” the city closed his son’s horizons. Mid-week, he goes “home to school, then straight back home again.” Ciclovía offers him an escape.

“It created a generation that has looked at the street from a completely different perspective,” says Jaime Ortiz, an architect and one of the original founders of Ciclovía, as he watches a toddler make her way down the Septima on a scooter. “Just think what she will think of this city in 10, 20, 30 years time. She will never forget this.”

Ciclovía takes in huge swathes of the metropolitan area, looping through the affluent north, down some of the city’s biggest traffic arteries, past street vendors selling watermelon and empanadas, sweetened black coffee, and orange juice.

“It started as a citizen protest that the city was becoming too car-focused,” says Jorge Mauricio Ramos, who runs the city’s free bike school and spent 10 years overseeing Ciclovía. “Today we have around 1.4 million people every Sunday. It’s part of our patrimonial heritage.”

For kids, one of the program’s greatest virtues is providing a space for recreation in a dense urban metropolis.

“It provides a space where people can be physically active, and that is especially important for lower-middle income residents who don’t have other options,” says Olga Lucia Sarmiento, a professor in public health at Los Andes University. Another benefit, she says, is that it takes children away from electronic devices. “Being outdoors for children is very important. They are moving, doing some physical exercise and they are not in front of a screen,” she says. “Various generations use it together so its very important for families.”

Ramos says the scheme’s other success for kids is in creating a place where “our children feel safe going out to have fun. It feels like an extension of their driveway.”

Some of the city’s children learn by following their parents, decked out in helmets and elbow protectors. But others choose to go to the city’s free bike school, where they can waddle along on a balance bike or pedal for the first time out of the way of the traffic.

The school teaches adults as well as children, and sometimes whole families turn up for the sessions, but the beauty of getting children started so young, explains teacher Fernando Perez, is that they learn faster than any adult.

“Children are quick,” he says, watching his youngest protegees cycle up and down an empty car park one Sunday morning. “They are less afraid.”

One of the few criticisms of Ciclovía is that as a Sunday program it is more about recreation than transportation, and so has not addressed the serious mobility and pollution problems that the capital faces. And in a city like this, those are not minor issues: Bogotá, which sits in a bowl in the Andes mountain range, is a capital plagued by dirty air. On days when it is particularly bad, a dense cloud of pollution hangs over the city. On Sundays, by contrast, when the city rests, you can usually see from the mountains in the east to those on the other side of the valley. It offers a vision of what a city with cleaner public transport, more bike paths, and fewer cars might look like.

Sergio Montero, an assistant professor of urban and regional development at the Universidad de los Andes, says part of the power of the scheme has been in showing how cities could be designed, and run, differently.

“Since the 40s, when the automobile started becoming dominant, cities—or streets—have been designed for cars,” Montero said. “People have internalized that that is how cities look and so assume that’s normal, that the streets are dedicated to cars.

“When you see that these spaces can be used for other things, walking with your children, jogging, biking, people start to think differently about how this space can be used, how much space the cars use up,” Montero said. “That’s the symbolic power of Ciclovía.”

This scheme is widely popular with just about everyone. Even many of the taxi drivers are enthusiasts. One I asked said he loves to go out walking with his wife when he isn’t working.

So, why don’t more cities adopt similar weekend cycle paths?

Hundreds of delegations have come to Bogotá to see how it works, and there are now Ciclovías across the Americas, though none as extensive or regular as here.

The big problem for most places, experts say, is the expense. In Bogotá, the district estimates the cost to be less than 10 U.S. cents per user each week. “That’s like nothing,” says Ramos. But U.S. cities like Los Angeles (which runs CicLAvia four times a year) and New York have seen costs skyrocket with organizers often liable for policing costs and insurance.

Another key factor in making a scheme like this a success is political support. Bogota’s Ciclovía scheme has gone through various iterations, losing mileage in the 80s, battling political opposition in the 90s, but eventually it became so popular among the population that it gained permanence.

“But one of the lessons we have learned during 40 years of doing this, is you can never take support for granted,” says Montero. “Just because one mayor or administration decided to do this it does not mean that the program will stay like that forever. If you want your city to have a successful Ciclovía you need political will, people convinced that this brings public health benefits.”

During his first term in office, Bogota’s current mayor Enrique Peñalosa, who is seen by many as a champion for cyclists, said that “a quality city is not one that has great roads but one where a child can safely go anywhere on a bicycle.”

While that might only be the case in this city on a Sunday, it’s a start.