In the 1950s, 3 out of every 10 people on the planet lived in a city. Today, that ratio has nearly doubled — and the United Nations projects that by 2050, nearly 7 in 10 people will live in urban settings. Our population is gravitating towards cities, and this shift is creating amazing opportunities as well as critical problems that need our immediate attention. Modern cities are hubs of connection and creativity and, at the same time, centers of pollution and dehumanization.

City 2.0: The Habitat of the Future and How to Get There is a new TED Books anthology that seeks to answer some of the key questions about how to develop thriving cities — tackling everything from issues of sustainability to infrastructure to the happiness of urban dwellers. Born out of The City 2.0, a broad initiative for citizen-powered change that began with the 2012 TED Prize, this collection of essays offers potential answers to the question: How can we ensure that our cities are sustainable, efficient, beautiful and invigorating? Produced in partnership with The Atlantic Cities, the 12 authors featured in this book offer fascinating ideas, from transportation to food to public art.

Over the next three days, we’ll hear from three City 2.0 essay authors. Today, we sat down with Diana Lind, the editor-in-chief and executive director of Next City, to discuss her essay that envisions cities without highways.

Why do highways have a bad effect on cities?

While highways connect cities that are hundreds of miles apart and allow us to move people and goods across this vast country, many highways were built at the height of suburban development. They are not designed to bring people into cities so much as to allow people to drive past them. As a result, these highways often bisect neighborhoods, cut cities off from their waterfronts and obstruct the natural development that occurs along boulevards and streets. The land beside or under urban highways is often underdeveloped, creating no-go zones that are bad for the city’s economy, safety and appearance. Highways carry loud, polluting cars, and research has shown links between road pollution and asthma. The impervious highway surface creates stormwater runoff and heat-island effects, which are bad for a city’s resilience in climate change. And unlike other kinds of property, highways don’t generate tax revenue, preventing dozens of acres from being productively used. Simply put: highways are a blight on livable cities.

I don’t think we should keep investing in highways. In this era of climate change, downtown revitalization and population density, they can no longer be the solution. As cities see their highways become structurally obsolete, it’s a perfect time to start thinking about how to connect cities through other modes of infrastructure.

What are some of the alternatives to highways?

Any plan to replace a highway needs to account for the cars that will be displaced. Ideally, you replace a highway with more transit options so people can take a bus or train instead of a car. In New York, when the city decided not to replace the West Side Highway, it cleverly took federal highway funds and used them towards improving transit. In San Francisco, a former highway was replaced with a trolley line. The footprint of the highway itself might become a boulevard, property for new development, a park or a bike lane. On a larger scale, our national network of highways should be replaced with a better rail network that allows people the option of taking a train between cities rather than having to choose between driving or flying.

You say in your essay that more walkable neighborhoods contribute to lower foreclosure rates. Why would that be?

It’s plain math. Imagine a couple that has to pay for two cars in addition to a mortgage; they’re less likely to be able to handle their monthly bills. Each car costs the average driver nearly $9,000 a year. Compare that with a monthly MetroCard pass in New York City — it’s less than $1,250 a year, and that’s as expensive as public transit gets. If you can bike or walk to take care of your daily needs, life gets even cheaper. The money saved on not owning a car actually helps keep people in their homes.

You also say that there’s a connection between highways and obesity. Share more on that!

It’s really a connection between obesity and driving. Researchers have found that driving and obesity have a shocking 99 percent correlation. The more you drive, the more likely you are to be obese, because you have less time to walk for daily errands and otherwise be active.

What have been some of the benefits of replacing highways in New York and San Francisco?

There have been many. Removing the highways has increased area property values, significantly reduced car traffic along these thoroughfares and reconnected both cities to their waterfronts. Local gems such as San Francisco’s Ferry Building and the Hudson River Park in New York are just two examples of how improving the area instead of improving highways has resulted in deeper investments in the city’s assets.

City 2.0 is available for Kindle and Nook, as well as through the iBookstore. Or download the TED Books app for your iPad or iPhone.

The City 2.0 is an online forum that showcase stories and projects for urban innovation, and also doled out 10 grants for thinkers with great ideas for cities throughout 2012. Here, meet 8 of the winners and hear their fascinating ideas »