Cycletracks separate bikers from cars and trucks, creating a safer and more inviting environment for riding. (Bill O’Leary/The Washington Post)

Our country has faced a challenge like this before and triumphed.

Pity the driver who dared attempt a cross-country road trip in the early 20th century. Consider what an engineer for the primitive Lincoln Highway suggested motorists bring along for such a journey: a shovel, an ax, a four-foot hardwood plank, 50 feet of rope, 16 feet of cable and a pistol.

The advice comes from F.H. Trego, who appears in Earl Swift’s “The Big Roads,” which chronicled the creation of the Interstate Highway System. Part I of the book is appropriately called “Out of the Mud.”

The $130 billion project, despite its flaws, is arguably the United States’ most important infrastructure ever. It connected the country and stimulated the economy.

Today, biking in your average American city doesn’t involve muddy roads, and there’s no need for an ax or shovel. But biking across town too often requires one to pack bravery, and a tolerance for stress. While bike commuting has grown 60 percent over the last decade, it remains a blip on the national level. (Bicyclists account for 0.6 percent of all commuters.)

Experts say that for cycling to truly blossom in the United States will require networks of cycletracks — bike lanes separated from vehicular traffic by vertical barriers — so that bikers of all ages can ride without fear of serious harm.

Plopping a “cyclists may use full lane” sign on a street with a 40 mph speed limit is like inviting someone to swim with sharks. Creating bike lanes, denoted with paint, is better, but still isn’t always appealing to someone who cherishes a peaceful commute. To become a truly bike-friendly country means building robust networks of cycletracks throughout U.S. cities.

“Protected bike lanes are huge,” said Gabe Klein a former transportation official in Chicago and Washington, D.C., who is now a special venture partner at Fontinalis Partners. “If somebody has a four-mile ride to work and half a mile of it feels unsafe because it’s exposed to traffic, they won’t do it.”

U.S. cities are already seeing the impact of when cyclists are given a separated place to ride.

The National Institute for Transportation and Communities looked at bike traffic on nine U.S. roads after cycletracks were added. Across the board bike traffic grew, ranging from 21 to 171 percent. This jibes with research showing that cyclists say they are motivated to ride when routes are buffered from traffic noise and pollution, and paths separated from traffic.

Portland has previously found that 60 percent of its residents were interested in cycling, but also concerned. Austin, Tex., polled its residents in 2013 and found that 55 percent would ride on a protected bike lane.

“The old adage if you build it, they will come is absolutely true,” Klein said. “If you fill all the streets with cars, people will think they’re supposed to drive. When you start to build these protected bike facilities, it’s a complete game-changer.”

While the aforementioned gains some cities have seen are significant, they pale in comparison to the potential of complete, fully built-out networks of cycletracks, where every city resident is a few blocks from a completely protected bike lane.

“There’s a quantum leap we have to make to give our cities connected bike lanes,” said Northeastern professor Peter Furth, who studies transportation and has lived in the bike-friendly Netherlands. “Only then can you really realize the benefits. If there’s a great bike lane here and a great bike lane there, but I can’t get from one to the other — I have to put my life at risk, I get myself feeling all stressed out, then it won’t work.”

Furth describes living in the Netherlands as a transformative experience. The country has seen the gains good cycling infrastructure can bring.

In 1970 the United States and the Netherlands had similar rates of traffic fatalities per 100,000 residents. Then the Dutch began emphasizing multi-modal transportation, such as biking. Now the Netherlands’ fatality rate is 36 percent of America’s.

Cycletrack networks bring other health benefits. Americans have put on a few pounds since the Interstate Highway System emerged. The average American man and woman have gained about 25 pounds each. With cycletracks, it’s easier to have an active lifestyle because daily tasks like commuting or running errands include a workout.

With safe, protected bike lanes, young people would be more independent. A kid who is too young to have a driver’s license could get around without relying on their parents.

“There would be an incredible impact on youth,” Furth said. “They can get around independently on bikes very well starting at age 12. It can make a huge impact for getting to school, getting to soccer practice.”

Cycletracks are also a tool to fight climate change. The more appealing biking is, the less likely Americans are to get in their cars and burn fossil fuels. We could transform the United States to a country built for 21st-century challenges such as obesity and climate change, and the price is reasonable.

Former Portland mayor Sam Adams has said that the initial buildout of the city’s 300-mile bike network cost the same as one mile of highway. (Of course, this presumes the highway’s costs are on the high end of what is typical.)

It’s difficult to estimate what a national installment of cycletracks in U.S. cities would cost. But the cost would certainly pale in comparison to typical transportation projects. Bike infrastructure can range from $100,000 per mile to a few million. For example, Austin estimated a 200-mile network of on-street bike facilities would cost $290,000 per mile. Building 47 miles of urban trails would cost it $2 million per mile.

But first we’ll need a sincere commitment to building safe bike infrastructure, so that all Americans feel comfortable riding.

In the 20th century, U.S. highways became safe enough for people of all ages to enjoy. Now in the 21st century, a similar opportunity beckons with bikes.

“Our standard should be, would you let your 8-year-old ride on that street? Would you let your 80-year-old grandmother ride on that street?” Klein said.