When researchers Ralph Buehler and John Pucher looked at thelatestrelease of national data showing how people are traveling around, they were stunned. The numbers ― official government data ― showed that over nearly two decades, there had been no increase in the amount of time people are walking and cycling.

The number of daily trips made by walking or biking ― whether running errands or getting to work or school ― hadn’t changed from 2001 to 2017.

“I just couldn’t believe it,” said Pucher, professor emeritus in urban planning and policy at Rutgers University in New Jersey. “It just didn’t make sense to me.”

But upon closer inspection, the two researchers realized why. And what they discovered was even more unsettling: Despite an increase in cycling among adults, there had been a dramatic decline in the amount of time children spend walking and biking each day.

From 2001 to 2017, there was a 34% decrease in the number of trips made by walking each day among children ages 5 to 15, and a 55% drop in their daily cycling trips, according to the researchers’ calculations.

“That’s a very disturbing trend,” said Buehler, associate professor in urban affairs and planning at Virginia Tech.

Their research, published in January, reflects a trend that stretches back decades ― to 1973 ― of children cycling less as a way to get around. In addition, recreational cycling for children ages 7 to 17 has dropped 48% since 1997, according to the National Sporting Goods Association.

One major reason for this, the study argues, is that our streets are simply not set up for bicycling or walking. More investment is needed to create safer cycling and walking infrastructure so that children are able to better navigate the streets by foot or by bike. The inequitable and insufficient urban planning that caters to cars over vulnerable populations comes with a big cost: our children’s health.

Riding bicycles during a community car-free day. (Photo: CHRIS DELMAS/AFP via Getty Images)

Unpacking all the reasons why fewer children are walking or biking to school or the corner store ― as opposed to cycling as a sports activity ― is complex. Causes include safety concerns, such as perceived “stranger danger,” the risk from distracted drivers and a lack of bike lanes. Geographic issues such as school consolidations mean many families live too far from school for bicycling back and forth. And lifestyle changes such as the amount of time spent in front of screens have eaten into daily schedules.

Both the World Health Organization and the U.S. Centers for Disease Control and Prevention recommend that children get at least 60 minutes of physical activity each day. If a child walks to school, and, say that journey takes 15 minutes to 30 minutes, “you’re guaranteed half of your physical activity per day,” estimated Cass Isidro, president and executive director of Safe Routes Partnership, a national nonprofit that promotes safe walking and cycling to schools. Add to that physical education classes or other sports, she said, and kids will easily meet the minimum.

But that’s not happening. Gym classes across the country are being cut, and after-school programs aren’t as prevalent, Isidro said.

The question we need to ask, she pointed out, is: “How do we build environments around schools that bring us back to the healthy way being the easy way?”

Related Video: Cops, Kids Connect Over Biking in Randallstown

The CDC warns of the impact sedentary living can have on children, namely obesity and associated health risks such as diabetes and asthma. And research by Nike found that, for the first time in history in the developed world, today’s children are expected to live shorter lives than their parents due to inactivity. Increasing the amount of physical activity children get doesn’t just improve their health. It also boosts student concentration, studies have shown.

Increasingly, there is the “digital pull to be on a device and be engaging with the world through that rather than be physically out and doing something,” said Lindsay Goldman, director of marketing and membership at USA Cycling, the national governing body for bicycle racing in the United States. This wasn’t a tension previously experienced by older generations, she said.

But one of the biggest challenges is the way cities are built. As the study states: “Unsafe, unconnected, or non-existent walking and cycling infrastructure is probably an important reason for low walking and cycling rates among children.”

“Combined with longer trip distances and greater concern for the safety of their children,” it continues, “the lack of good infrastructure has become an even greater deterrent to walking and cycling to school.”

Separated, protected bicycle lanes are safer for cyclists and drivers. (Photo: Britta Pedersen/picture alliance via Getty Images)

Ensuring that streets are safe for people of all ages means going much further than just painting bike symbols on streets, the researchers argue. It requires a variety of pro-cycling policies such as well-planned bike routes away from cars and support for bike-sharing schemes.

“I think many cities are going in that direction,” said Beuhler. “But very few U.S. cities have achieved that.”

The study identifies 12 bike- and pedestrian-friendly cities where there has been significant growth in walking and cycling: Boston; New York; Philadelphia; Washington, D.C.; Miami; Chicago; Minneapolis; Denver; Seattle; Portland, Oregon; San Francisco; and Los Angeles.

On average across these urban areas, the number of people who commute by bicycle rose 146% from 2001 to 2017, while 12% more daily commuting trips were made by foot over that same period. This is compared with the national average of just 0.4% more people biking each day to work and fewer people walking to work.

These 12 cities have prioritized the needs of cyclists far more than the rest of the U.S., according to the study. While the cities together represent only 7% of the country’s population, they accounted for 47% of U.S. protected bike lanes in 2018, and 44% of the country’s bike-sharing programs.

But even if a city invests in bike infrastructure, that doesn’t mean everyone feels safe.

“If you only have a bike line, or protected bike lane, for a couple of blocks and then there is an intersection and then there are five blocks where it’s sort of ‘good luck’ and then the bike infrastructure picks up again, that’s not good enough to get somebody who is more risk-averse to ride a bike,” said Buehler, adding that the same goes for walking. If there aren’t enough crosswalks or sidewalks, or the distance between them is too far ― a symptom of what he said is “designing around cars” ― risk-averse people are less likely to make that trip.

“We have to design infrastructure and networks of infrastructure for walking and cycling for everyone,” Buehler said. “And not just for those who are more daring and risk-taking.”

Top of the list among the most vulnerable road users are children. And with at least 40,000 traffic deaths annually over the past three years in the U.S. ― including 857 cyclists killed in 2018 ― it’s no small risk.

“As a parent myself, it’s unnerving to imagine sending my child out to ride around the neighborhood on a bicycle when there are such high incidents of distracted driving, people texting and driving, and other roadway accidents,” said Goldman.

The U.S. might want to take inspiration from some European cities, which have seen cycling flourish.

Amsterdam, considered one of the world’s most bicycle-friendly cities, was spurred to rethink its roads and ultimately create the 22,000 miles of bicycle paths after the deaths of 400 children in traffic crashes in 1971. Today, Dutch students aged 11 and 12 must take a written and practical exam to show they understand the rules of the road when biking. A national cycling advocacy group helps take the students out on the streets to practice riding on their own.

Meanwhile, in Seville, Spain, segregated bike lanes have been heralded by campaigners as a huge success. These types of lanes ― where the bike lane is physically separated from the road for cars with a barrier, fence or raised curb rather than just painted lines ― allow people of all ages to navigate their way around the city. According to one report, 39% of all cyclists in Seville last year were under the age of 29. More women are also biking ― from 25% of all the people cycling in 2006, a year after the initiative began, to 36% in 2017.

Cycling rates among men remain more than twice as high as among women. (Photo: David Bohrer/Los Angeles Times via Getty Images)

Separated bike paths are “absolutely crucial” to encouraging vulnerable populations to bicycle, said Pucher. Children, women and elderly people ― often more risk-averse demographics ― are, on average, cycling less than men, according to Pucher’s study. Cycling rates among men, for example, were more than double the rate of women in 2001 and in 2017.

Protected bike lanes don’t just help keep cyclists safer. As a study published last year found, protected and separated bike lanes were also linked to lower fatality and injury rates for people in cars.

“Roads can be an unnerving place to be and nobody wants to send their kids out on roads that feel dangerous,” said Goldman.

“I think it’s a disconnect,” she added. “A lot of times as a driver, you almost de-personify a cyclist, and just see them as this thing or impediment or something in your way.

“I think if people stopped for a moment and really thought, ‘That’s just a person and it’s only going to take me three seconds to wait to pass them safely,’ that would really go a long way to creating a safer and more hospitable environment for cyclists.”

Yet, building streets for cars continues to win out. According to the study, cumulative federal funding for pedestrian and cycling projects only came to 2% of all federal roadway spending from 2001 to 2017, even though walking and biking represent 10% to 13% of all daily trips taken in the United States.

“If you make driving more attractive, guess what people will do ― they will drive,” said Buehler.

It’s not for lack of demand though, said Isidro. People want the ability to walk to the local coffee shop and to allow their kids to ride bikes down the street without worrying, she said. What’s needed is government funding at every level to support this, “because the demand and the will is there.”

“We all remember what that was like, to take off on your bike down the block for the first time, that sense of freedom, of autonomy, of knowing your environment, being able to make decisions in your own space,” Isidro said. Supporting this and making it safer “gives our kids a chance to grow.”

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This article originally appeared on HuffPost.