In the following interview, we speak with Jeff Speck, author of Walkable City: How Downtown Can Save America, One Step at a Time. Speck is an architect and city planner in Washington, D.C., oversaw the Mayor's Institute on City Design, and served on the Sustainability Task Force of the Department of Homeland Security.

Speck explains the four areas that must be addressed in making a city more walkable -- the walk must be useful, safe, comfortable, and interesting -- and what's involved in achieving these qualities. Walkability can be difficult and costly to create, but fortunately it's not necessary to transform an entire city; even a single walkable street makes a difference.

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Isaac Pino: Just a few more questions before we open it up for your questions.

There's a couple of things that you usually mention when you talk. Let's go ahead and go through -- we might not have time for the entire 10 steps, but what are the elements that make an area or a neighborhood walkable, and the things that you bring up in the book?

Jeff Speck: The 10 steps ... I still haven't reconciled this. It's a little bit of cognitive dissonance in the book. The 10 steps are really four categories, but I had the four categories for a long time, and I wanted more than four chapters, and everyone likes 10, so there are 10 steps.

One chapter deals with biking, one chapter deals with transit, one chapter deals with parking only. There's a chapter on each issue, but what I've been learning and lecturing on now for about a decade is this hierarchy of four requirements. Each one is necessary and not, alone, sufficient.

That is, if we're going to convince Americans to walk -- particularly in places where they don't have to walk, which is most of America; everyone still has a car -- the first step to getting people to have fewer cars is to actually say, "OK, yes, you all have cars, but maybe there are circumstances where you'll choose not to use your car."

If you want to create pedestrians by choice, as opposed to just need, the walk needs to be useful, the walk needs to be safe, it needs to be comfortable, and it needs to be interesting. We've touched on some of these issues.

The useful walk has to do with the proper balance of uses within walking distance and, of course, linking walkable neighborhoods together properly with transit and handling parking properly.

But most American cities -- I'm not talking about the Washingtons or the New Yorks, but the Grand Rapids or the Oklahoma Cities, or the Dallases, even -- do not have the right balance of housing downtown. It's only when they get a lot more housing downtown, in the one part of their city that has the potential to be walkable, that it will perhaps achieve that end.

There are exceptions, but most American cities don't need more affordable housing downtown; they actually need more market-rate housing downtown. They typically have a vast overload of affordable subsidized housing downtown, and nothing else, in many cases.

The safe walk is the part that most people who talk about walkability tend to talk about, which, unfortunately, a lot of people think is all you need to do. It's about 100 things, of which most cities get about half wrong, and it starts with the size of your blocks.

There's a clear correlation, inverse correlation, between block size and safety, for pedestrians. A study of California block sizes -- you double the size of the block, you triple the number of deaths of pedestrians. Which then goes into the number of lanes: Do you have the right number of lanes? Do you have more lanes than you need? You probably do. It depends what kind of city.

Then all the little details, down to the radius of curvature on the curbs at the corner, which used to be so nice and tight that you could just put a stone there, and now it's a 40-foot swoop because things have been redesigned around specialists like fire chiefs and pro-speed highway engineers.

I spend a lot of time in my book completely -- and I hope effectively -- discrediting the traffic engineering profession, which is an utter farce. Don't get me started.

Just read that part of the book. I'm waiting for someone to challenge me to a debate against an angry traffic engineer, but most of the traffic engineers I meet come up to me and say, "You're right. My profession is an utter farce." And yet, that's the profession that, more than any others, has controlled the form of our cities in this country.

The comfortable walk is the most counterintuitive aspect for many people, which is that we all love wide open spaces, climbing mountains to see long views. We may not want to climb the mountain, but we love the long view.

But we forget that all animals seek prospect and refuge. Refuge means that your back is covered. Predators can't get you. It's in our DNA -- I'm not sure about the proper term -- we can't help it. Millennia of survival have taught us to not be comfortable in places without good edges, so as planners we try to create outdoor living rooms, and nothing's worse than a surface parking lot, or just a missing tooth -- an empty lot.

We'll turn around, and you see it on Main Street after Main Street; I'm sure you've all seen this. You go to a wonderful historic town like Rhinebeck, N.Y., and you're walking down this great Main Street, and all of a sudden you're just like, "I'm done. I'm going to turn around."

Why? Because the strip center, built in the '70s, has pulled back from the sidewalk. Every other store was just nice, right there with the front door against the sidewalk, and then the strip center pulls back, the parking lot's in front, and you're like, "I'm done walking." We need that, to feel comfortable.

Then, finally, interesting has to do with, yes, you can define spaces well with building fronts, but if it's a blank wall or a parking structure or something else ...

A number of cities, particularly in Europe, even have "active façade" policies that actually demand a certain number of openings per linear foot, or linear mile -- I guess linear block, probably -- to ensure that pedestrians aren't bored as they walk, because we are such a fickle species.

That's the final point, that achieving these four things is really, really hard, which is why the last chapter of the book is a concept that I bring to all my work, that I learned from Andres Duany, my boss and mentor, which is called urban triage. Recognizing that most American cities -- even the most walkable American cities -- are not walkable, but you only need a limited area that functions in that way. There will always be the bad streets for the Jiffy Lubes and the Dunkin' Donuts, and that's fine.

Most cities feel this obligation to make the whole city walkable, and they sprinkle the fairy dust equally. The mayor feels an obligation to the whole city. "Let's make the whole city beautiful." But of course the whole city ends up really mediocre, because the only way to achieve those four things is to really focus, focus, focus a lot of investment and a lot of effort in a limited area.

A lot of cities that are known for being walkable, like Greenville, S.C., there's really just one street, one great street. Because it's so hard, it's really important to get that focus.