Editor’s note: Welcome to Grist’s presentation of Alex Steffen’s new book Carbon Zero. We’ll be posting a new chapter every day till we’re done — here’s the full table of contents. And this post will tell you a little more about the project. If you like what you read, you can order Carbon Zero from Amazon.

Urbanism: Why good walksheds mean lower emissions

How we build our cities determines how we live in them.

If we are going to imagine a carbon zero city, in most cases we need to start with a fresh understanding of how we get around in them. Transportation, after all, generates the largest share of humanity’s greenhouse gas emissions. Cars account for most of that, but it’s not just driving cars that’s causing those emissions. Though the oil we burn driving is a catastrophic problem in its own right, those emissions are only part of the climate impacts of a huge set of systems that enables our driving. Factories and dealerships, roads and highways, parking lots and gas stations, road repairs and wrecking yards — put them all together, and these “automotive systems” represent the single biggest contributor to global climate change worldwide.

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So, getting a 90 percent reduction in transportation emissions is a serious job no matter where we live. But it’s a giant task in many North American and Australian cities, where car ownership and use (and thus emissions) are far higher than in cities elsewhere, and where most planning decisions were made with car traffic foremost in mind.

One thing is clear: We can’t get to new possibilities with old thinking. Turning the ignition key and starting our car — no single act more defines the 20th century’s idea of prosperity, or offers a sharper contrast to the realities of the 21st century. Business-as-usual forecasts predict the world’s car fleets will double or even triple by mid-century. Car companies, with their old assumptions, see nothing but growth ahead. If their assumptions were right, there would be no way we could drop transportation emissions by the roughly 90 percent we seek.

Electric vehicles

What about electric cars, though? Can’t we just make all our cars electric and be done?

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It’s true that an electric car charged with clean energy emits essentially no greenhouse gases while being driven. The big problem with electric vehicles is that they do nothing to counteract the large share of automotive-system emissions that don’t come out of the tailpipe. Running a car on electricity — or fairy dust, for that matter — won’t make the factory in which it is manufactured, the car dealership in which it is sold, the highways on which it drives, the mechanic’s shop in which it is serviced, the parking lots on which it sits, or the junkyard in which it dies, emit any less CO2.

Even beyond that, though, there seem to be sharp limits on the number of electric cars we can get on the road. Carmakers have been extremely resistant to manufacturing EVs. Even now, hybrids and electrics make up less than 1 percent of all vehicles on the road worldwide. And since it takes years to bring out a new car (from design to dealership) and more years (18 years, by the best estimate I could find) to replace even America’s fleet of cars (and in poorer countries, cars are kept on the road much longer), simply replacing every car in the world with electric vehicles is unlikely to happen in a reasonable time frame. Indeed, a recent Pike Research study found that even with a predicted increase of 4,500 percent in the number of EVs on the road by 2017, they will still only make up 3 percent of the global car fleet.

I wholeheartedly agree that pretty much all cars should be efficient electric vehicles. I also agree that electric cars are well-suited for cities, have advantages to offer as car-sharing vehicles, and can help provide storage capacity to a smart electrical grid — three points EV advocates make frequently and with good cause. We need to acknowledge, however, that the option of taking hundreds of millions of cars off the road by replacing them with electric vehicles in the next 20 years is not realistic. Better cars can be part of carbon zero cities, but we can’t just change the kind of cars we drive and leave everything else the same.

Not transportation, but urbanism

How then do we get that 90 percent reduction? By thinking in new ways that better fit the reality of our times.

Because we’re so dependent on our cars, when we think of improving transportation, we tend to think only of how to avoid traffic jams and speed cars along more quickly. This approach isn’t working on its own terms, leaving aside the demands of the climate crisis. Unfortunately, in a thriving city, when we fight traffic, we lose every time. We’ve spent more and more money on creating wider streets, building more bypasses and highways, but traffic itself hasn’t gotten better. In large part this is because of an effect called “latent demand.” In a growing, car-dependent city, many more people would already drive today if driving were more convenient; therefore, the minute we build a bigger highway, or widen an arterial through town, or eliminate stoplights on a busy street — increasing the capacity of those roads to carry traffic — more people start driving again. Sometimes you buy yourself a few years of reduced traffic, but even the most successful highway construction projects inexorably lead back to gridlock. You just can’t build your way out of a traffic jam, and when you try, you end up with packed streets, polluted air, and bankrupt local governments.

But the problem we need to solve isn’t traffic: It’s access. Transportation is all about access through mobility. We want easy access to our workplaces, to our kids’ schools, to the doctor’s office and hair salon, to the theater and the church, to the shops that carry the products we want, to the bars and restaurants where we meet our friends. In the second half of the 20th century, planners envisioned a world where access to all of the goods and services we needed would be provided by mobility — if we wanted something, we’d drive to get it. The result is the landscape we see today, especially in the suburbs, where millions of people take many trips a day in their cars just to keep up with their lives. With our communities arranged this way, there’s little choice but to drive. When we provide access through mobility, we grow ever more dependent on our cars.

Compact communities and access by proximity

We have another choice, though: access by proximity. Simply put, access by proximity means building neighborhoods where the things we want are nearby. Compact development — building neighborhoods that feature a mix of homes, businesses, and community amenities within easy walking distance of one another — brings the things we want closer to the places we live. The most climate-friendly trip is the one we never take in the first place, because what we want is already close. Compact development is the key to quickly converting as many climate-damaging car trips into climate-friendly trips-we-never-take. It prioritizes building better places, not busier roads.

Urban density reduces the number of trips residents take in their cars, and shortens the distance they drive for the remaining trips. It is possibly the best-documented fact of urban planning that the denser the neighborhood (all other things being equal), the less people drive, and the more their transportation emissions drop. If their neighborhoods are compact enough that many of their needs are within their “walkshed” (the area they feel is within a convenient stroll, roughly about a half a mile in every direction for most people, though a wider area for fit young adults), the amount of time they spend in their cars can drop dramatically.

How far can this go? How dense is too dense? We haven’t yet hit a point where the connection between denser neighborhoods and less driving breaks down. People drive less in New York than Los Angeles; they drive less in London than New York; they drive less still in Singapore than London. Certainly, the connection between density and low transportation emissions holds true at any level of urban density Americans are likely to see in the near future. If we want one simple guideline for reducing our car emissions, it’s this: Make our communities more compact. Density is destiny, when it comes to transportation.

That said, not everyone wants to live in cities as dense as Singapore. Luckily, we don’t have to in order to create big changes. Densities that are much lower, more akin to the way small towns were laid out before the car, can provide sufficient cohesion to change the way communities get around, while densities more like the core neighborhoods of San Francisco or Brooklyn can stir dramatic shifts.

Most of the time, transit isn’t practical at low densities. It only starts to become practical as enough people live within walking distance of a transit point, like a bus stop or light rail station, to make running a bus or train worthwhile. Once more people do live in a neighborhood, any increase in population makes things better: more neighbors just means demand for even better transit. This is part of the reason planners push to have the areas around stations built up in “transit-oriented development.” The more people who live near transit, the more practical transit becomes.

Compactness also makes transit work better. Planners have long noted a phenomenon they call “transit leverage.” Simply put, transit leverage means that people who ride transit some of the time tend to drive less the rest of the time. Every mile a transit rider goes on public transit results in between four and nine fewer driving miles (depending on the community). That seems strange — one mile of train travel, say, should only displace one mile of driving, since they’re both forms of transportation. In reality, though, urban transit travel is different: People usually walk or bike to and from transit stops, which means they tend to plan their trips a bit more carefully than drivers do, and as transit ridership grows on any particular route, more businesses and services locate along the route to serve those riders. This means that a person who, say, walks to the station and commutes by train to the office, may well go to the gym and grab a coffee on the way in, then shop for a gift, hit happy hour with some friends, and buy a few groceries on the way home. What would have taken someone in a car a number of trips, the transit rider achieves on a round-trip ticket.

Compact communities bring more destinations closer together; this alone promotes walking. While it is certainly possible to have unwalkable density (think office parks of towers surrounded by parking lots separated by busy roads), in general, having more people around means more pedestrians, slower traffic, and safer streets (crime drops precipitously when there are lots of people walking in an area). At the same time, having walkable streets helps people in a compact community gain more access to their neighborhoods. Compact communities and walkable streets are symbiotic.

People-focused streets and deep walkability

What makes a place walkable? It’s not complicated: good sidewalks, pleasant public spaces, street trees and benches, and so on. A number of excellent primers exist describing what makes a place more walkable. My favorite is Jan Gehl’s Cities for People. Gehl describes walkable, compact neighborhoods as “people focused,” which I think is exactly right, and about as elegant a description possible. If, when walking, you feel like the neighborhood is focused around your needs, then your community is doing it right. If you feel that the experience of walking is unpleasant, even dangerous, then your community is doing it wrong. Simple. (The same, in general, is true for biking, though sometimes the needs of bikers need to give way to the needs of people who are walking.)

The more people-focused neighborhoods a city has, the better those neighborhoods work. Walkable streets experience what we call “network effects.” Having the only telephone in the world would be pointless. Having one of 20 is better — you now have people to call. Having one of billions makes your phone into a universal form of communication. That’s a network effect.

The process obviously applies to transit: Living close to the only transit line in a city is better than nothing, but when you live near multiple lines going different places and connecting to a variety of other lines going still more places, then transit opens up the entire city to you. With good planning, transit can quickly become not only cheaper and greener than driving, but also faster and more effective. Driving across the city through traffic might mean you’re stuck in snarls for hours — while an express train hurtles by, delivering its passengers to a mesh of connecting services that can get them anywhere they need to go. When the network effects of transit kick in, they make possible something no individual transit line can accomplish.

Accumulating benefits works even more powerfully for walking. Living within one small walkable area is pleasant, but if that area is bounded by barriers like highways, unbridged rivers, developments with no thoroughfares, or just streets that feel unsafe and dangerous, that small walkable community begins to feel like an island, rather than a starting point. What cities need instead is something I call “deep walkability.”

Deep walkability describes a city in which a person can walk to almost any destination along great walking routes, a city in which walking is a viable means of getting from any one neighborhood to another, or even all the way across town. (The same, it might be said, applies to deep bikeability, though bicyclists can more easily share existing roads, even where no bike lanes exist. On the other hand, walking in the middle of the road is an excellent way to get killed.)

When compact communities function like nodes on networks of transit, bike lanes, and people-focused streets, they tip the balance of convenience away from cars. More walkable urban neighborhoods served by more ways of getting around: that’s the closest thing we have to a simple solution to climate change. A world in which most people called livable, walkable, transit-served, compact communities home would be a world well on its way to the deep reductions in transport emissions we need.

Rebuilding the suburbs

Driving through America’s suburbs, it can be hard to see all this walking, biking, and transit use happening there anytime in the future. Looks can be deceiving, though.

It’s important to remember, first of all, that “suburb” is pretty much a catch-all word that we use to mean “places that are not core cities, but not farmland, either.” That single term hides a huge diversity of places, from just-built pods of McMansions selling a taste of country life on the far urban fringe, to classic streetcar suburbs which can be difficult to tell apart from their neighboring city. When the discussion is about compact community and walkability, the term “suburb” is not a very useful one. More useful are the terms “inner ring” and “outer ring.”

The inner-ring suburbs are the first suburbs, built up into the 1960s and 1970s. Often they featured more modest family homes on smaller lots, and had streets with sidewalks and trees. Quite often, inner-ring suburbs grew up around an old small town main street or along commuter rail stops. The result is that the inner-ring already has a range of places, some of which already have a great neighborhood feel and people-focused streets. A fifth of all Americans call these inner-ring suburbs home (52 million people, according to a report by the Brookings Institute).

Big opportunities await these older suburbs. Because many inner-ring towns have “good bones” (they’re already compact and walkable, at least in places), they have something to build on. Because they’re close to central cities, they could be in high demand. With the right combination of new housing to raise densities, new investments in transit and walkability to make that density desirable and an emphasis on their existing strengths (parks, schools, historic buildings, and so on), many inner-ring suburbs could grow into places that have a people-focused, small-town feel. This would make them both much less auto-dependent and much more competitive in the regional housing markets.

It won’t be a simple task — on top of the obviously hard work of attracting new investment and building new systems, many older suburbs have huge fiscal challenges with declining tax bases, aging housing stock and infrastructure, and (in some places) increasing concentrations of low-income residents pushed out of the more expensive central cities; quite a few inner-ring suburbs have experienced sharp decline in the last 10 years — but retrofitting suburbia for walkability and compact community offers at least the opportunity for an economically competitive (and low-carbon) future.

It’s harder to be sanguine about the future of the outer-ring suburbs, especially the very fringe suburbs often called “exurbs.” Many of these suburbs are not only dependent on lots of driving, they were designed for it, top-to-bottom. In many cases, trying to walk their feeder roads and arterials falls somewhere between unpleasant and suicidal. Densities are too low to support realistic transit of any kind. The existing infrastructure, as crusading civil engineer Chuck Marohn points out, is unaffordable: These suburbs already don’t have the tax bases to maintain their spread-out roads and utilities and this problem will worsen as oil prices rise and the demographic shift towards cities continues. (Marohn calls the financing of suburban development over the last 30 years “a Ponzi scheme.”) Several million homes already sit vacant and unwanted in the exurbs; millions more may go unwanted in the near future. The outer-ring suburban model faces permanent foreclosure. Nothing the U.S. or Canadian federal governments can realistically do will save that model. It simply makes no sense. I fear that people who stay in the outer-ring suburbs (because, say, they’re under water on their mortgages and can’t afford to sell their homes) are going to find themselves in what become essentially sprawling ghettos, lived in mostly by those too poor to live anywhere else (this is already becoming the case in many places across the Sun Belt).

What brave outer-ring suburbs could do is try to save themselves by remaking their communities into something new. A smart suburb could bid to draw new growth, radically redraw its street plans, invite innovative small-scale redevelopment projects, lobby for transit service and think about how to shrink its infrastructure commitments to something fiscally sustainable … and it might work. I don’t know any outer-ring suburb that’s done that yet, but it seems possible, given sufficient motivation to chart a new course.

Healthier cities

Living in people-focused neighborhoods will also mean we live longer, healthier lives, on average.

We’re just beginning to get a real sense of how deeply connected illness and unsustainable living are, but it’s very clear that people in walkable, compact neighborhoods live longer (and live in better health) than suburbanites.

Density itself makes for safer streets — studies find that “a 1 percent increase in urban density translated into a 1.5 percent decrease in traffic deaths and a nearly 3.5 percent decrease in pedestrian fatalities” — but walkable density is even healthier. A recent study published in the American Journal of Preventative Medicine showed sidewalks were the main factor influencing physical activity, and that cross-culturally, people who live in a city neighborhood are twice as likely to be physically active than those living in the suburbs. In this light, the well-documented correlations between rates of obesity, diabetes, and heart disease and the amount of time a person spends driving are not surprising. Indeed, the health benefits of walking are so great that researcher Alan Durning found:

[W]alking 30 minutes a day, five days a week, adds 1.3–1.5 years to your life, on average. (More vigorous exercise adds even more.) On reasonable assumptions … this relationship means that for every minute you spend walking, you get three back. Time spent walking, then, is utterly free. It’s time you would have spent dead.

Less traffic in your neighborhood also makes you healthier. Fewer cars, driving more slowly, means you’re less likely to be hit and killed by a car (ending up as one of the more than 30,000 Americans who die from car collisions each year; not to mention the hundreds of thousands who are injured or the $99 billion in losses the Robert Wood Johnson Foundation estimates are caused by car crashes). Fewer cars means healthier local air as well, which is good since as many Americans die from the effects of air pollution as from breast cancer and prostate cancer combined — more than 70,000 a year.

“If doctors and other health experts designed our cities, they would look quite different than the sprawling communities we see today,” says Sonal R. Patel, MD, of the American Lung Association. “Cities would provide more healthy choices, more opportunities for walking and biking, better access to transit, less congestion, more housing close to workplaces, and more parks for kids and families to enjoy.”

Land use has a massive impact on our health and safety. It’s also clear that other changes we want to see in a sustainable community — from more access to healthy food to a broad shift away from toxic chemicals in manufacturing and household goods — have big health impacts. Though no one to my knowledge has yet done a comprehensive, holistic study of the health benefits of the transition to a carbon zero city, my suspicion is that those benefits will prove to be mutually reinforcing and profound.

This is good for us. It’s also good for the planet. Right now, health care as an industry is a major source of climate-changing pollution. Many of those emissions are spent treating people with chronic but preventable lifestyle illnesses. With a combination of much healthier citizens, more sustainable practices on the part of hospitals and insurance companies, and more closed-loop and low-carbon design principles incorporated into medical equipment and supplies, I find it pretty easy to imagine a carbon-zero health-care system. That alone would account for a non-trivial slice of the emissions cuts we need to make. Given what we know about the dire public health impacts of climate change, it seems to me that the health professions have a special duty to lead through their own practices.

The coming urban boom

I bet you’re wondering, how much can we actually change the way our cities are built? Don’t neighborhoods change slowly? Isn’t transit expensive and doesn’t its construction take forever? How realistic is any plan that begins with changing the fundamental land-use patterns of many of our communities?

These objections make sense — if we take the past as a guide. Decades of public debate and pop culture have defined cities in our minds as places that struggle with poverty, decline, and “white flight”; places that are desperate for any economic leverage, and need to build every casino, stadium, urban mall, and parking garage they can to attract suburban shoppers and business investment; places that physically change only incrementally and in a scattershot manner. We see cities as sickly, weak, barely hanging on. In fact, this view of the city is outdated and inaccurate.

We are now entering the largest worldwide city-building boom in history. Here in the United States, the Census Bureau predicts the population will grow to as much as 365 million people by 2030; 85 to 90 percent of them are expected to live in urban metro areas. In much of the developing world, a transformative explosion in city-building will likely happen between 2030 and 2050 — as rising urban populations meet growing economic capacities — but in the U.S. that urban surge will happen in the next two decades.

“More than half the built environment to be seen in 2025 did not exist in 2000,” says the demographer A.C. Nelson. “During the next generation planners may have an unprecedented opportunity to reshape America’s built landscape.” And because of the housing bubble and the Great Recession, only a tiny amount of the needed construction has begun over the last few years, meaning that most of the new building we’ll need to meet this population surge has yet to break ground. This “unprecedented opportunity” means that big thinking is the only realistic kind of thinking to do.

Not every city will grow. Here in the U.S., some industrial cities seem likely to continue their decline because of economic transitions that have been decades in the making and will not be easily reversed. Others will find they’ve made decisions that start them down a different path of decline as their suburban tax bases decline and auto-dependent systems become more and more expensive to maintain. (Indeed, I anticipate that the decline of auto-focused cities over the next decades will be a national crisis of the same magnitude as the hollowing-out of the Rust Belt, although it’s a crisis we could largely avoid with bold action now.) Others still (especially in the American Gulf Coast states and the desert Southwest) will find life made difficult by changing climate conditions: droughts, dust bowls, water shortages, worsening tropical storms, invasive species, and new infectious diseases. Some places will actively try to limit growth by making it harder to develop in existing communities (a strategy which only leads to a nasty combination of rising costs of living and more sprawl). A growing urban population is not a tide that will lift all boats; it may send many struggling boats against the rocks.

Successful urban regions, however, will grow more rapidly than ever before, seeing their populations swell by hundreds of thousands, even millions, of new residents in just the next few decades. All those people will need homes, workplaces, hospitals, schools — and transit to connect these venues. Cities and regions that embrace the opportunity and make smart choices about where and how to build will have a once-in-a-century chance to reweave their urban fabrics.

The growth these new residents bring can reshape whole neighborhoods, provide the revenue for investments in new infrastructure and systems, and stoke the fires of a bright green American economy. The coming boom can release a revolution in urban innovation.

And this boom will be largely urban. A huge cultural change has happened in the last 20 years, and we’re only now beginning to understand it: People, especially young people, now greatly prefer walkable urban-core neighborhoods to car-focused suburbs. This is true even in North America, where the conventional wisdom has been for years that most people prefer suburbia. Studies show millennials want not dream homes, but dream neighborhoods. Recent Census Bureau stats reported, “64 percent of 25- to 34-year-olds look for the city they desire to live in before looking for an actual job.” The 2011 Community Preference Survey, the largest and most in-depth real-estate poll in the U.S., also shows a dramatic shift: “Seven times more people say the neighborhood where a house is located (88 percent) is a bigger consideration in deciding where to live than the size of the house (12 percent) … More than three-quarters of the public (77 percent) consider having sidewalks and places to take walks important … Young singles (under 35) are especially likely to [place the highest value] on a neighborhood with a mix of houses and businesses.” This trend is most pronounced for the young people cities most want to attract. A 2011 CEOs for Cities study found “In 2000, young adults with a four-year degree were about 61 percent more likely to live in close-in urban neighborhoods than their less-educated counterparts. Now, they are about 94 percent more likely.”

At the same time, we’re changing not only where we live, but also how we live. People are living longer, having fewer kids later in life, and living in nontraditional households and relationships. Families with young kids at home make up only about one-fifth of American homes, according to the latest census. Expectations about what makes a good childhood have changed as well: Many younger parents now see urban childhoods as better than suburban ones (they’re certainly safer — kids are much less likely to die in or under a speeding car when they live in a walkable community). The result of all this societal change is that demand for smaller homes, townhouses, studios, and lofts seriously outstrips supply. Indeed, some real estate experts say there’s a latent demand for tens of millions more units of urban housing than we have, while perhaps as many as 40 million unwanted suburban homes continue to see dropping values.

All this means that the coming city-building boom is really a boom in people-focused, compact communities. Indeed, one factor that’s keeping many cities from growing is simply cost: With supply lagging so far behind demand, housing in walkable neighborhoods commands a steep price premium. One study commissioned by CEOs for Cities found that a one-point increase in a home’s Walk Score (which rates a place’s walkability on a score from one to one hundred) corresponds to an average increase of $3,000 in that home’s value. With such a gap between housing demand and supply, walkable neighborhoods are simply financially out of reach for many people who would like to live in them, and are increasingly becoming too expensive for the less wealthy people who live there now.

The answer to this problem is simple: Build more housing. The simple truth is that if you want home prices to drop, or even just level off, the only way to do this is to build more housing. Every known policy aimed at limiting housing costs — from rent control to tenants’ rights to development moratoria — has failed to stop the rise in housing costs. Some of these policies have other merits (I think tenants’ rights ought to be strengthened in most cities), but none can do anything about the central dynamic, which is that in a city with extreme housing pressures, every sale of a property drives out a lower-income family and replaces them with a higher-income family; if that city has added little new housing supply, the lower-income family’s only option is to move out of the city to where housing is cheaper. Desirable cities in growing regions either add housing rapidly or become unaffordable and socially inequitable. It’s that simple. Limited housing supply is what drives out the poor.

A major factor limiting compact development, though, is that many people — especially older people — still have mixed feelings about growth, and fear that more development will “ruin” their neighborhood. At first glance, this makes intuitive sense: lots of new growth in a small area might seem like a recipe for neighborhood decline. It is definitely possible to design bad buildings — we’ve all seen an eyesore replace a cherished landmark somewhere in our town. Buildings can be ugly and imposing; when they are sited badly, lack pedestrian amenities, and offer no public or commercial uses at the street level, they can even become a form of “vertical suburb,” wherein they remain auto-dependent despite their density. That problem, however, is solvable with good planning and higher expectations of developers (expectations they’re often happy to meet if in return they’re given speedier permitting for their projects).

Bad buildings are one thing; bad streets are entirely another. Though we may not know the term, we have all experienced the “paradox of intensification.” As density increases, the number of people who choose to walk, bike, or ride transit also increases, but traffic increases as well (albeit more slowly). New walkable areas emerge, but many residents still need to drive; people from outlying car-dependent suburbs still want to drive through the neighborhood; old drive-in businesses still draw traffic; and parking is harder to find, meaning more cars circling looking for a spot. Often, new residents arrive before the businesses and amenities to serve them, meaning favorite parks, cafes, and restaurants get crowded. Clashes between pedestrians and drivers not used to negotiating urban settings become more common. The result is that a little density, arriving slowly, can end up making a neighborhood more congested with traffic, noisier, more dangerous, and less pleasant.

These are the perils of incrementalism. Small steps and gradual change may seem to take us “in the right direction” but may actually be more difficult (and arouse more local animosity) than making a larger change quickly. The main way incrementalism fails in this context is when planners try to “balance” the needs of cars with the needs of people walking, riding their bikes, and using transit. No such balance exists. As you add density, auto-dependence demands more and more parking spots, increased road capacity, and fewer impediments (such as traffic lights) that “get in the way” of cars. Without these, driving as we’re used to it in suburban settings only gets worse as more residents arrive, adding more cars to the streets.

Car-free places

We can’t build our way out of these traffic jams. We can bypass traffic, though, by creating other options for mobility. Driving will simply never get easier in a dense city. The only known fix to this problem involves remaking the streets for people, not cars. We know that with just basic pedestrian infrastructure (like sidewalks and streetlights), people will begin to use transit at about 12–15 units per acre. But we also know that this “transit-supportive density” is just one tipping point. If within key neighborhood cores (or along important corridors), cities aggressively tip the balance toward making streets that are designed to slow traffic, limit cars, and make for wonderful pedestrian-focused places that are well served by transit, at a certain density level — hotly debated, and in my opinion partially determined by culture and climate, but generally thought to be between 30–40 units per acre — many people will choose to get rid of their cars altogether, and most people will choose not to drive for most trips. Transit-supportive densities transition to car-free densities. That’s correct: Plan well and build quickly, and many people will simply use their cars less or get rid of them.

Urban people make these choices on their own — when their cities work well. Simply increasing density and focusing streets on the people walking and biking will set these changes in motion, as more and more residents find it preferable to leave the car at home for most trips, and more people passing through the neighborhood find it better to either take transit into the area or to simply find another route to get where they were driving. (A certain amount of “geographic sorting” has already begun taking place, with a certain number of people who feel driving and cars are essential moving from cities to exurbs that still have wide arterials, big parking lots, and highways — a topic I’ll come back to in a future project.) The more friendly the neighborhood gets to people on foot, bike, and transit, the easier it gets for others to decide to make the switch.

This is what’s known as a “threshold effect,” a paradoxical situation wherein a bit of change makes things inconvenient and slightly more change can produce some serious negative side effects, but lots of change actually improves substantially on the original situation. A few more people living closely together but still driving makes street life worse; many more people living more closely together in a great neighborhood, though, ends up reducing traffic. The more people who live without cars (or don’t use them much), the better the neighborhood gets as it densifies.

Areas designed to support car-free lifestyles can end up giving people more mobility. This is totally counterintuitive for most North Americans. A century of advertising and six decades of planning focused almost entirely on cars have convinced us that cars are always the quickest, most convenient way to get from one place to another. Indeed, most transportation planning is actually traffic planning — its only and entire goal is to move as many cars as possible in the shortest amount of time. To the average old-school transportation planner, the city’s main job is moving cars. Many traffic models don’t even count people biking and walking, much less the effect of bundling their trips on a neighborhood walk; some don’t even count transit. In short, both our cultural expectations and the traditions of road engineering tell us that cars are transportation, and therefore, anything that reduces cars must reduce mobility, and anything that reduces mobility must impoverish us. Slowing, much less limiting, cars is disastrous (they claim) and will lead inexorably to gridlock and economic losses.

The reality is that travel times can actually improve with fewer cars. Streets designed for pedestrians, bicyclists, and transit can accommodate many more people, moving more quickly, than can congested, car-focused roads. (This is one reason why “bus rapid transit” (BRT) works so well. Buses can fly through the city, moving many more people than cars could, when they have lanes of their own.) More users means better transit service, with more frequent trains and buses (“shorter headways” in transit-geek terms), better connections and transfers, and more express routes — all of which means it takes less time to get from one stop to another. In many places with bad traffic, biking (or even walking) is already quicker than driving some routes. With safer streets where pedestrians and cyclists get shorter paths, less waiting time at lights, and more areas with no cars at all, many routes will get even quicker. A low-car city can be a faster one.

These trends can be reinforced by creating congestion pricing zones where drivers are charged a toll for using the streets — even with traffic calming obstacles and more road lanes devoted to public transit, tolled areas can actually end up with less traffic than they began with, as was the experience in London. Eliminating free parking and allowing new developments to be built without parking in the first place — free/cheap parking is an inducement for people to drive — can help reduce the number of cars on the road at any one time even further. Narrower streets with fewer cars don’t always lead to less traffic, but these trends do mean that low-car cities don’t have to be driving nightmares.

Low-car cities don’t eliminate cars, but they do put them in their proper urban context. Some cars are likely to be a part of our cities for the foreseeable future. Whenever we have a choice, though, between making it easier to drive and making it easier to walk, bike, and ride, the cars need to make way. Perhaps most importantly, urban streets should constantly remind drivers that when they do get behind the wheel in cities, they’re moving through people-focused places, and must exercise responsibility and care.

A top priority for any neighborhood should be reducing the speed at which cars move through its streets. For one thing, faster cars are deadlier cars. When a driver going 20 mph hits a pedestrian, the pedestrian’s risk of dying is roughly 5 percent; when a driver going 40 mph hits someone, that person’s risk of death rises to 80 percent. Driving faster is particularly deadly to young children, who, studies show, have a harder time seeing and anticipating fast-moving cars. Car-on-car collisions, too, are more likely to be deadly at higher speeds. (The higher risk involved with fast-moving cars is one reason why the statistics show suburbs are now more dangerous for children than urban-core neighborhoods.) Finally, fast traffic is noisy, unpleasant, and stressful for those on the sidewalks of a busy street — it’s a nuisance as well as a danger.

The answer is not lowering the speed limit. It’s not street signs indicating pedestrian crossings. It is not even more stoplights. All of these are useful tools, but the real answer can be found in changing the shape and feel of the streets themselves. Widening sidewalks and reducing the number of lanes of traffic — the so-called “road diet” — makes drivers pay more attention and feel the need to slow down. Putting in speed bumps, obvious crosswalks, and curb bulbs at pedestrian crossings does, too. Planting street trees and other features that “crowd” the road, making drivers feel higher speeds are more stressful, also does the job. When drivers feel they must pay attention, they drive more carefully and slowly; a fair number of drivers who were just passing through on their way to other locations will simply begin to avoid the area. All of these things have the added benefit of making the neighborhood more walkable.

Better still are places where cars are either forbidden, or are given an obviously low priority. Many cities around the world have older cores where cars are only allowed for commercial purposes or if owned by a resident. Often, these streets are closed off to cars by automated bollards that can only be opened with the right electronic passes. Other cities have embraced design strategies that make an entire street a pedestrian zone, essentially one giant sidewalk through which cars can pass, but only carefully, and slowly. Still others have simply banned cars from certain roads or at certain times of day, creating part-time pedestrian boulevards. And many more efforts to build strongly people-focused cores are on their way. Cities from Singapore to Vancouver to Melbourne are looking at ways to create large shifts away from the private car, while the European Commission has put forward a strategy for all cities in its jurisdiction to create plans that will completely remove all gas-powered cars from their centers by 2050. Meanwhile, significant shifts in opinions about car ownership and usage have already occurred, with fewer and fewer young people even getting drivers’ licenses, and the number of vehicle miles traveled dropping steadily in some cities. Many urbanites already want people-focused, even car-free, communities.

The threshold effects of people-focused density make building more of it the single most critical task for carbon-neutral cities. If we’re going to see the shifts in transportation choices that are pivotal to addressing the climate challenge, we need to design policies to quickly turn car-dependent areas into vibrant compact walksheds. That means our cities must grow denser. In a perfect world, this density would simply spring up because it’s needed and wanted; in this world, though, density doesn’t happen magically on its own, even when there’s a gigantic demand for it.


One way to build more density quickly is the creation of new “ecodistricts.” Often built on “brownfield” sites (like old military bases, vacant industrial land, abandoned ports, or dead malls), ecodistricts offer a great advantage: by building an entire neighborhood from the ground up, planners can use the latest infrastructure and planning from the start to make these areas people focused and transit friendly. Some districts — like the Vauban neighborhood built on a decommissioned military base outside of Frieburg, Germany — have been designed from the start to encourage minimal dependence on cars (living in a compact community with bike lanes, pedestrian streets, and a new tram into the central city, 70 percent of the families in Vauban don’t own cars). Others have emphasized energy efficiency (like districts in Malmö, Sweden, or the Dockside Green community in Victoria, British Columbia) or sustainable waste management (like the Hammarby Sjöstad area of Stockholm). We’ll come back to this idea of district systems. It’s important. Cooking up a new neighborhood with new infrastructure and sustainable transportation planning baked in is almost certainly the easiest recipe for a bright green urban community.

Unfortunately, opportunities to build a whole community from scratch are relatively rare. Every city probably has a few large sites ripe for ecodistrict redevelopment, but not many thriving cities have more than a few. If we’re really going to change the fabric of a major city, we need to talk about remaking existing neighborhoods, bringing them up to the level of people-focused density needed to support transit and new infrastructure. Sustainable urbanism most often means reweaving an existing, worn fabric, not producing new cloth.

Those with experience in North American urban politics, though, may understandably despair of the idea that we can bring entire neighborhoods up to 30–40 units per acre, when many are now less than 10 units per acre and so many challenges stand in our way. In many cases, because of a wide range of factors, including limited public resources, the perils of incrementalism, the slow speed of change in commercial development, and Not In My Back Yard (NIMBY) politics, increasing densities over an entire area consistently and quickly seems essentially impossible. But is it?

Smart neighborhood infill

Spreading density evenly, like butter across a piece of bread, is only one approach to transforming a given walkshed. The average person is willing to walk only half a mile at most for most trips. That means that her walkshed is essentially a circle a mile wide around her home. That area contains a little more than 500 acres. If we were to raise the density everywhere in her walkshed from an existing average density of say 10 units per acre to 30 units per acre over the course of two decades, every single block would have a number of new buildings (or significant remodels) on it.

Technically, there is nothing preventing us from doing this, and improving neighborhoods in the process. We certainly can make older neighborhoods better with lots of small interventions that add new residents. Larger homes (for which there’s less demand as average household sizes shrink) can be split into apartments and condos; small backyard cottages can be built; basements can be converted (or second stories added) to create new modest apartments or “granny flats”; new townhomes and small apartment buildings can replace vacant lots (or tear-down buildings) and be designed in such a way that they feel part of the existing fabric of the neighborhood. Combined with traffic calming, bike lanes, street trees, and green spaces, good infill development can ensure that neighborhoods retain their charm while reaching people-focused density.

The problem is that in practice, urban politics often makes this almost impossible to do in the time we have. Subdividing homes and redeveloping small lots can only happen at a slow pace, as properties become available. Permitting, planning, and infrastructure costs are high for local government, since almost every new project is particular and costs more staff time while new tax revenue is slow to arrive. NIMBYs may oppose new cottages and townhouses. Developers may be reluctant to risk money on complicated infill projects when easy money can still be made building elsewhere. We should certainly continue to encourage good fine-grain neighborhood development; we just shouldn’t expect miracles. If we want people-focused densities within the next couple of decades, we need to look to a more innovative set of approaches.

Tentpole Density

A non-intuitive characteristic of density is that it works on averages. You can get to 30 units per acre in a walkshed by having every acre covered with 30 units, or by having a single 300-unit building sitting on 10 acres of land. That means (with good placemaking) a few dense places can make a whole area perform like a more compact community. A dense neighborhood core (like an old small town “main street”) can raise the whole community around it to people-focused average densities. Like a tentpole, this compact core lifts the effective density of the urban fabric around it, even if those surrounding blocks don’t change very much.

Consider a hypothetical: A 500-acre walkshed that is currently at an average density of 10 units per acre could add just two units per acre (almost imperceptible — a couple of basement granny flats or backyard cottages on each block) to most (400 acres) of its area if it made its neighborhood core really attractive to new development. If, in that center, a people-focused core was 180 units per acre (six- and eight-story mixed-use buildings over a 40-acre area), and a surrounding belt of blocks was 60 units per acre (with a mix of townhouses, cottages, and small condos, say), the neighborhood’s average density would rise above 30 units per acre. The overall effect would be that everyone in that walkshed would have a people-focused community — but 80 percent of the neighborhood would look no different.

Or think about it another way: Imagine you live in the “bungalow belt” of older homes in a single-family neighborhood that grew up around a streetcar line. You love your block, with its classic homes and old trees. You can walk five blocks to a nice little “main street” with a few shops, a cafe, and a bar or two, but that little neighborhood core doesn’t offer access to everything you need. There’s no grocery store within walking distance, say. You would take transit downtown to work, but the bus only comes every half hour. The nearest decent daycare is a 10-minute drive. As a result, both you and your partner have cars, you drive almost everywhere you go most days, and your daily drives take you past run-down strip malls, parking lots, and a lot of wasted land just outside your neighborhood. This is a typical scene for many people in North American cities.

Now, imagine the same neighborhood, but with those strip malls redeveloped, those parking lots turned into mixed-use buildings, and that wasted land used for infill development. Now, you have not only your “main street,” but also a whole corridor of people-focused buildings within walking distance. The thousands of new residents who live there make an enticing market, meaning that a grocery store opens up on the ground floor of one of these new buildings; child-care options improve; there are more places to dine out. Due to increased demand, the bus now runs every five minutes. New stoplights are installed and more street trees are planted. A new park is being built with the increased local tax revenue, and more young parents mean the school system is pressured to improve. Your actual living situation has barely changed, if at all. You still live in a little bungalow on a quiet street with big trees. Except now you and your partner find it easy to get rid of one of your cars, and you drive a lot less (and save a lot of money). You now live in a people-focused community.

A dense neighborhood core is, of course, only one of many possible patterns. Some cities focus on creating these neighborhood-centered “urban villages.” Others focus on key corridors, stringing compact development along key roads and creating linear density. Still others group most of their new density in smaller clusters along new transit lines. Forms can (and should) vary to reflect local cultures and conditions, but the operating principle remains the same: The key is to concentrate on spots where enough growth can be clustered to create transformation throughout the local area.

Tentpole density means we don’t need to completely remake every street — let alone convince every person to change her behavior — we just need to concentrate our efforts on building walkshed cores that can offer access by proximity and many more choices to nearby neighbors. Tentpole density can provide critical mass for new transit, infrastructure, and business investments. These tentpole neighborhood centers make a ton of financial sense to local government. They can be much more easily planned, permitted, and financed than myriad small projects, and be built more quickly at a reasonable profit (while adding to the local tax base). They can also be built simultaneously with new transit, street improvements, and amenities paid for by borrowing against the new tax revenues they will generate — an old, proven technique known as “tax increment financing.”

When new buildings tip the balance in their own walksheds, they not only improve quality of life in the immediate area, they also offer benefits to the surrounding neighborhoods. People in nearby walksheds gain new destinations for shopping and entertainment. The transit routes, walkways, and bike paths that connect these cores together mean bikers and transit riders in other neighborhoods along the way get better service. As more businesses catering to car-free customers (by, for example, offering free delivery) locate in the area, residents who want to drive less benefit, wherever they live. Retrofitting even a dozen such people-focused neighborhoods can redraw the transportation picture of an entire city.

The placemaking dividend

A critical mass of people-focused neighborhoods can also power economic reinvigoration. Simply put, people-focused density is economically more competitive. Numerous examples show that sidewalk-focused retail (restaurants, small shops, local professional services) does better as density increases and the area becomes more walkable. The idea that urban neighborhoods need to “compete” for suburban shoppers by providing lots of free parking and widening streets to ease traffic is outdated and counterproductive. The fact is, at a time when suburban retail is crashing, urban retail is beginning to boom.

Indeed, the “placemaking dividend” retail businesses get by being in a walkable neighborhood can be huge. From Vancouver to Copenhagen to Melbourne, dense walkable neighborhoods have become entertainment destinations, drawing people from around the metro region to new restaurants, bars, theaters, and arts institutions. New York City Department of Transportation’s Janette Sadik-Khan reports that the stores lining the newly closed-to-cars streets in Manhattan saw sales increase 71 percent in just one year, and the effect is now spreading to nearby streets. Even as the number of new auto-dependent supermarkets has plunged in recent years, smaller pedestrian-focused (and, more frequently, locally owned) urban grocery stores are multiplying.

What’s more, in many places, the success of the cores of these neighborhoods has enlivened businesses at their margins. There’s a “spillover effect” that can help more entry-level small businesses thrive in the cheaper edge locations. This means immigrants, artists, and others often find more opportunities in these areas, despite rising rents — especially if local government makes helping them a priority (by, for instance, encouraging mobile food carts, or making small business licensing easier for small stores, art studios, and temporary retail).

All of this means more money stays in the local economy, generating more jobs and prosperity in turn. Even the construction involved in walkable cores is better for the local economy. A 2010 study shows that building bike lanes creates 14.4 new jobs per million dollars spent and widening sidewalks means 11.3 jobs per million bucks, while road upgrades and repairs only create 7.4 jobs per million bucks. Some highway projects generate less than three jobs for every million dollars in taxpayer money spent.

And once these walkable centers are built, they provide much more revenue for our local governments than spread-out, auto-dependent development does (studies show that compact, mixed-use development generates far more sales and property-tax revenue per acre than low-density uses like strip malls and single-family streets), while costing much less to maintain (the infrastructure costs per resident are much lower in compact communities, because more people can share the same sidewalks, pipes, and wires, much more efficiently). Compact development simply costs less to serve and provides more money for our parks, schools, libraries, and emergency services. In other words, walkable centers provide a foundation for better governance.

Walkshed technologies

The same walkable places also provide fertile ground for technological innovation. Mobile and ambient technologies (our cell phones and laptops, embedded sensors, database technologies, augmented reality, and so on) not only thrive in people-focused communities, they multiply, intermingle, and evolve. These “walkshed technologies” are morphing the ways we live in people-focused places. They’re changing cities irrevocably. And mostly, this is a very good thing.

I’m old enough to remember a time before Google. Back then if you wanted to find something on the Web, you had to go looking for it, using these sites called “directories.” You would pull up a directory, click on a category of thing, and then go one by one down a list of webpages until you found something like what you wanted. The Web was “browsable,” but not “searchable.”

Today, that seems utterly absurd. Yet until the explosion of smartphones about five years ago, nearly everyone still used cities like the Web before Google. If you were out shopping and wanted to find which store had the best price on an item, for instance, you generally had to either call the stores one by one or go around and compare their prices in person. Even at home, most people still used the Web like the phone book, finding the number for a store or restaurant online then calling and asking them if they had the right product or an open reservation.

Today, every smartphone is essentially a small computer. Every phone can access maps, reviews, retail offerings, service data, and a whole host of other facts and opinions about how things work in a given city. And phones are now ubiquitous: according to the International Telecommunication Union, there are now 5.9 billion mobile subscribers worldwide (the number of total users is less, but 85+ percent of all people now have access to a phone). Our cities are now, as Adam Greenfield says, searchable.

On the most basic level, technology has simply dematerialized a bunch of trips we used to make. For instance, fewer and fewer people drive to a music or video store since they can download music and stream movies. Other trips we used to make have been replaced with home delivery. Most purely functional shopping can now be done online, with the products you buy delivered to you. Because one truck driving multiple places (often on a computer-generated route designed to take the least time and use the least fuel) is far more efficient than many people driving themselves around to shop, home delivery is inherently more sustainable. Delivery is even getting more secure, with innovations like the German Postal Service’s packstations or Amazon’s “delivery lockers,” which keep deliveries in secure neighborhood kiosks until you pick up your parcels with a swipe card. If we live in walkable communities, we can now get most of the things we need in life without even owning a car (I suppose many of us could get most of the things we’d like to purchase without leaving the house).

When we do want to go out for a bit of “sport shopping” or “retail therapy,” it’s easier than ever to have the things we buy while out and about delivered to us — indeed, some stores are now simply “webfronts” designed to give a tactile, personal experience to online shopping by letting us handle the products or try on the clothes before we buy them online. Shopping is less and less about driving around and filling up the car trunk than it is about taking transit to a retail district, meeting a friend and making a day of it, walking around and checking things out, having lunch, people-watching, having a drink and relaxing. Increasingly, it costs less to have a thing delivered than it does to pay for parking. In fact, the very degree to which physical shopping is becoming an experience rather than a necessary chore may drive rapid innovation in how retailers connect with, serve, and entice their customers. As Dan Hill puts it, “physical experience had better be bloody good if it is to withstand the force of the internet.” Shopping streets now survive by being great places to walk around and have fun.

But that’s not the limit of how technology is changing our relationship to space and transportation. Done right, dense cities with good technology actually become easier to move through. In fact, they’re changing the very nature of what it means to move through urban space.

It’s a common observation in some tech circles that this will be the last generation to know what it means to get lost, since phones with GPS-powered maps and travel information are ubiquitous and constantly available. What is less remarked is that this is probably the last generation to frequently experience unintentional urban solitude, and certainly the last generation to unwillingly experience the true sensation of being alone in a crowd. We nearly all carry access to enormous amounts of media around with us, allowing us to create our own emotional bubbles whenever we like. Most of us are communicating somewhat constantly with friends, family, and coworkers through phone calls, emails, and texts. Already some of us move through heavily annotated urban spaces, where we can in real time know where our friends are and what’s going on that might be of interest to us. As urban technology accelerates, and begins to include more interfaces and means of interaction, I expect that what we view now as an imposing degree of connection will someday soon look quaint and cranky.

Not all the effects of this will be good. Indeed, I think constant hyperconnection may be in some sense damaging to our souls, distracting us from the messy and constant work of becoming ourselves. Heck, we’re still reeling from the societal impacts of old-school broadcast media, which sociologists like Robert Putnam have argued (convincingly) have been a terrific shearing force on our communities, associations, and civic life; the social effects of ubiquitous and always-on communication may magnify those impacts. Constantly being alerted to choices can make our lives extremely stressful, as we’re constantly reminded of all we’re missing. “Filter bubbles” applied to our lives in urban space may render cities less and less a place of encounter and exchange. I suspect that — just as being able to schedule long blocks of uninterrupted time is now taken as a sign of prestige and power in upper-middle-class culture — finding, or living in, urban space that is random and whimsical on the one hand, or peaceful and low-stimulus on the other hand, may become an increasingly sought-after experience. (All these forces actually have the potential to be far, far more harmful when combined with auto-dependence and the social isolation of suburbia, but that’s a story for another time.)

On the other hand, it’s possible that we may get a grip on these technologies and use them to make our cities much livelier, more nurturing places. There’s a lot of evidence to suggest that more online socializing leads to more friendships and socializing in “real life.” Some groups have begun to find ways to use technology to engage with people who’ve essentially stopped participating in civic and cultural life. Approaches as varied as geolocative art to gamification are trying to draw people back into engagement with each other in urban places. It may be that hyperconnection, properly tamed, makes us more a part of our cities than we’ve been for a century.

In any case, some of the effects of walkshed technologies will be unquestionably good when it comes to energy use. For instance, the one gigantic advantage cars have always had over transit is convenience. Walkshed technologies are fast eroding that advantage. Since buses and trains are easily tracked with GPS, it’s trivial to provide information about when the next bus or train will be at our stop, thereby minimizing the time we spend standing around and waiting. It’s increasingly easy to have the system plan the most efficient trip for us given the real-time positions of the buses or trains we’re choosing from and current road conditions, meaning that we get to our destination by the fastest possible route. In addition, for people who are often occupied using their laptops, tablets, and phones, Wi-Fi–enabled transit means time that would otherwise be spent focused on not crashing our cars can be spent being productive or just enjoying ourselves. Seen in this light, all driving is a waste of the time you could spend doing better things.

Walkshed technologies actually increase the number of options we have, compared to driving. If we really want to drive, looking up the nearest car-share vehicle is easy, and many systems allow walk-up use: Find the car, walk there, get in, and drive away. Taxicabs, too, are easier to order and (since they themselves are networked and tracked) more likely to arrive quickly; services like Uber give us access to fleets of cars we can’t normally hail on the street. Even ride-sharing services get much more realistic. Some futurists, again including Adam Greenfield, even see an emerging era of “cloud commuting,” where a host of travel options is available for a given trip, and people move effortlessly through the most convenient ones, not needing to plan their routes, much less memorize bus timetables and subway maps. With the right phone and the right app, transit is effortless.

Walksheds as innovation platform

Compact communities suffused with technology offer another advantage: They’re a superior platform for the widest range of innovations. This is counterintuitive — exurbs, with more land and cheaper rents, seem like they’d be much more amenable to experimentation. But we think this because we mistakenly focus on surface form, and neglect to look beneath the surface, to systems.

When we look at exurban systems, what we find is that they are incredibly rigid (and thus also brittle, but that’s an idea we’ll take up again later). Because suburbs are so spread out, with roads built in hierarchies of cul-de-sacs, feeder roads, and arterials, with different parts of life (like home, office, school, and shopping) separated and widely dispersed, most exurbs can only realistically be navigated by car. That means connections between points can only be made in one way, and the only thing we can really change about exurbs — without making them into something other than an exurb — is the mechanics of driving itself (and we haven’t done a very good job of that in the last half century).

Within more compact communities, though, the number of possible connections increases geometrically as more kinds of people and more potential solution spaces find themselves within proximity to each other. Replacing auto-dependence with walkability means replacing a single, rigid approach with a variety of approaches. That means more can be changed, which in turn means more things for innovators to improve. Especially in the cities that welcome innovations in deeper systems, like infrastructure, patterns of urban life can be made flexible, approaches to problem-solving can be iterative and influence each other, and rethinking root problems becomes possible.

If you want to innovate, do it where you find the most opportunities for innovation.

City innovation as transportation solution

By seeing the problem of transportation for what it really is — a problem of access, of land use, of the way we build our neighborhoods (in other words, a city-building problem) — we instantly redefine the available solutions. In just a few years, a neighborhood can go from auto-dependent to people focused. In just a few more years, cities can weave together their people-focused neighborhoods with deep walkability and transit routes. Within a few decades, a fast-changing city can deeply slash its energy use.

The changes needed are changes that improve people’s lives, changes many people want (and most people who live in cities are eager to see). We’re talking about growing nicer neighborhoods, with broad sidewalks and street trees and local businesses; places with a mix of homes and people; places that are less expensive to live in, yet offer more opportunities; places that are healthier, cleaner, and safer for our kids. And perhaps most importantly, on a planet in the midst of a climate catastrophe, places that emit many, many fewer greenhouse gases.

Read the sidebar to this chapter: People-focused places and fairer cities

Read on: If we build it right, they (emissions) will come (down)