HARI SREENIVASAN: How is it possible that we're sitting in Times Square? What happened here that you made you think you could build this?

JANETTE SADIK-KHAN: Well, Times Square had been a tangle of traffic for almost 200 years, since it was first created and people had tried for years to fix it. They tried slip lanes and signal changes and nothing worked. And so I brought the idea to Mayor Bloomberg that we should try something bigger.

HARI SREENIVASAN: In 2009, Janette Sadik-Khan proposed closing Broadway to cars from 42nd St. to 47th St. and turning it into a quarter-mile long pedestrian plaza.

JANETTE SADIK-KHAN: And it started just with some traffic cones and some beach chairs, and it's really become a model for other cities to try things out. You can re-imagine them, test it, measure it.

HARI SREENIVASAN: The permanent redesign cost $27 million, and the city measured the changing traffic flow through Times Square using GPS devices in 13,000 taxis.

JANETTE SADIK-KHAN: It was much safer for both pedestrians and motorists. The traffic worked just fine. And it became an economic blockbuster. It became one of the top ten retail locations on the planet.

HARI SREENIVASAN: In her book "StreetFight," Sadik-Khan argues the nation needs to shift the focus of city streets away from cars.

JANETTE SADIK-KHAN: Our streets for so many years have been used to move cars as quickly as possible from point A to point B. And people have even forgotten that there are other uses for the streets. Whether to walk or to bike or to take the bus. It's not anti-car. It's really pro-choice. It's about providing options to make it easier for people to get around.

HARI SREENIVASAN: By 2013, when Sadik-Khan's tenure in Mayor Bloomberg's administration ended, the city had re-purposed 220 acres of space — taking away lanes from cars and giving them to pedestrians, bikes, and buses.

Sadik-Khan says dedicated car turn lanes, restricted bus lanes, and adjusting traffic light signals based on real-time traffic conditions helped increase average driving speeds in central Manhattan by nearly 7 percent.

At the same time, traffic and pedestrian fatalities in the city have declined.

JANETTE SADIK-KHAN: Our streets have never been safer. In fact with more and more cyclists on our streets, we've seen a one-third reduction in cyclist injuries and fatalities, while we've seen a quadrupling of people biking around.

HARI SREENIVASAN: Much of the increase in biking is from Citi Bike, the bike share program funded in part by Citibank and Mastercard that's been used more than 26 million times since launching three years ago. The Citi Foundation is one of the underwriters of this program.

JANETTE SADIK-KHAN: It was the first new transportation system in New York City in 60 years and at almost no cost to taxpayers. So I think it's a model, particularly in an era where we don't have a lot of federal funding and state funding and local funding is hard to come by.

HARI SREENIVASAN: Sadik-Khan says the huge number of riders actually makes biking safer.

JANETTE SADIK-KHAN: You're not going to ride the Tour de France on this bike… they're like heavy! Right?

HARI SREENIVASAN: Right.

JANETTE SADIK-KHAN: And I think that also goes a long way to calm down the streets.

HARI SREENIVASAN: New York City streets now have 400 miles of bike lanes, with more than 30 miles separated from vehicle traffic by a lane of parked cars, an idea Sadik-Khan copied after seeing it in Copenhagen, Denmark.

HARI SREENIVASAN: But with the new lanes came a backlash, including from drivers who complained bike lanes caused more traffic congestion. A 1.8 mile lane bordering Brooklyn's Prospect Park is still mired in litigation six years after being installed.

HARI SREENIVASAN: What do you think it is that creates that initial resistance to change, whether it's city street design planning or almost anything else? People get pretty comfortable with how a space looks and how a space is used, until they try something else, right?

JANETTE SADIK-KHAN: It's a really good question, because people are really attached to the status quo. And when you change the status quo, we find the status quo pushes back hard, right. And people have expectations that our streets are for cars. And they don't really have any other expectations that they can be anything else. So that was one of the innovations that we did in New York City. We moved fast to show that you could have change on your street, that it would be better. That you can build in other ways to get around just really by narrowing the traffic lanes and opening up that space for other uses.

HARI SREENIVASAN: With more than half the world's population living in cities — expected to become two-thirds by 2050 — Sadik-Khan hopes New York sets an example for a more person-centric view of transportation.

JANETTE SADIK-KHAN: I think it's really critical that we build in really good choices for people to get around — Making it safe for people to bike, making it fast for people to ride the bus, making it easy for people to walk around. Those are the kind of really secret sauces for 21st century cities. And really we get what we design. And when we design our streets to make them wide and as runways for cars, you know, that's what we get. And when we design our streets for people, and make it easier to walk and bus and bike, we get a much different result.