For Janette Sadik-Khan, growing up in New York City meant that the streets were her backyard, and riding the bus was one of her favorite childhood activities.

Sadik-Khan eventually made her love of transportation into a career, serving as commissioner of the New York City Department of Transportation.

Her goal? Reclaiming cities for people, not cars.

“We take our streets for granted, but the way streets are designed tells people how to use them,” says Sadik-Khan, co-author of Streetfight: Handbook for an Urban Revolution. “The way they’re organized defines how they should be used. Wide streets with wide lanes tell people in cars to speed. Streets with small sidewalks or less crosswalks tell people that they’re better off driving.”

And she believes that if we don’t transition away from cities with lots of car-owners, then we’re doomed to congested, failed urban centers.

That’s a problem. More than half of the world’s population lives in urban areas, and that number is on the rise.

“There’s never been more evidence that building new roads just encourages people to drive more. And there’s little evidence that new roads succeed in [lessening] congestion,” she says. “If you build an 8-lane road, you’re going to get eight lanes of traffic.”

So what’s the solution to all this doom and gloom?

Sadik-Khan believes that it all lies in using existing networks and providing more choices to riders. She points to cities like Chicago -- a city with over 200 miles of protected bike lanes -- and Houston, which revamped its bus system overnight.

According to Sadik-Khan, successful future cities will have more ring roads, car-free downtowns, and lots of pedestrians: “People who walk... are the ‘secret-sauce’ of cities.”

The other big upgrade? Better networks between cities, like the bullet train in Japan.

But there need to be some big changes before that happens. The U.S. spends, on average, about 2% of its GDP on transportation investment. Sadik-Khan thinks that number needs to be raised significantly.

It might be a while until we see the types of cities Sadik-Khan thinks we need. Until then, dust off your sneakers; walking more might be the best way to reclaim our streets.