Jane Jacobs' design tenets were mentioned in previous articles that I've written, but here they are again in short form:

1. Mixed primary uses that create traffic/vibrancy throughout the day
2. Short blocks to make neighborhoods more walkable
3. Mixed age and overhead buildings to enable a diversity of businesses
4. Population density

To put them in context, it's important to understand that Ms. Jacobs formed these tenets while observing her Greenwich Village NYC neighborhood (and similar ones) during the 1950s (the book came out in 1961). It was an urban world in the midst of a major transitional upheaval, as the car moved from a luxury to a standard household item for the middle classes. Cities at the time had been built around walking and mass transit, and accommodating the car was traumatic: too narrow streets, not enough parking, and freeways plowing through neighborhoods. Today, the vast majority of us live in an urban/suburban landscape built around the car - with accommodations for parking and major arterials and freeways - which makes the tenets seem almost quaint and disconnected from our modern world.

The problem as I see it is that these four principles have hardened into dogma in the urban planning community without really understanding the meaning and philosophy behind them. To some extent, I even think Jane Jacobs herself suffered from this too-narrow understanding of her own insight. Let's see if we can get to the true essence of these principles, and then talk about how they might apply to modern car-based cities.

The goal is a very subjective concept called "vibrancy." What is vibrancy? To put it simply, vibrancy means a buzz of people interacting and transacting in win-win exchanges - both economic and social. Vibrancy was very visible in Jane's world: people on the street and sidewalks, jostling and bumping as they went about their daily businesses, often in street-level retail establishments just off the sidewalk. In the car-based world, that vibrancy is more hidden. Sure, you can see the cars (sometimes way, way too many cars in congested traffic), but you don't really see the people or the interactions as they hide inside the cars, strip centers, and office buildings. They're there, but we don't "feel" them as much as we do in a classic Jane Jacobs walkable neighborhood.

Vibrancy starts with a very simple decision: is there some interesting or necessary activity that draws me out of my home? Work? Shopping? Socializing? Whether I'm in a walk-up apartment in New York or a house in the suburbs, the question is the same. More options increase the likelihood of drawing me out. And I have to weigh-up those interesting options against the barriers to going out, particularly mobility: how much time, effort, and money is required to go do this activity? A good, cheap restaurant is an easy choice when it's right down the street, but a harder one in heavy traffic with unpredictable parking or with some long walks and subway rides in possibly unpleasant weather. There's always leftovers in the fridge and something on TV, the mortal enemies of "vibrancy".

The flip-side perspective is that of the business owner: what kind of reasonable customer base will I be able to draw on? The more barriers between me and them, the less likely they are to patronize my business. What is my "draw zone"? The more people - and the more money - in that draw zone, the better my prospects. That means a larger diversity of businesses can be supported.

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Looked at through these lenses, Ms. Jacobs' four tenets make instant sense. If you assume walking as the primary mobility mode, distance becomes a major barrier to vibrancy. Taxis are expensive - not to mention a major pain to flag down, even in NYC - and transit is generally a hassle, slow, and loses time in waiting and transfers. Thus we need as many interesting activities and options as possible within as short a distance as possible to get vibrancy. Mixed-use and mixed-cost buildings increase the variety of options within that short distance - and more options increases the likelihood that one or more of them will be attractive enough to draw you out on a given day, evening, or weekend. Short blocks make walking routes more direct, and put more options within the same travel-time range. And density provides the raw fuel of consumers to keep all those interesting street shops economically viable. The more eclectic a business, the larger the draw zone - in size and population - it needs to stay viable: convenience stores and dry cleaners are easy - offbeat bookstores and sushi restaurants are harder to support. The mobility zones are so limited in this world, that the only way a neighborhood reaches critical mass for vibrancy is to stack as many people as possible right on top of the businesses: mixed-use and density.

In the car-based world, distance becomes far less of an impediment. Speed determines the "mobility/draw zone" - fast arterials and freeways with minimal congestion. Short blocks and mixed-use become somewhat irrelevant because the pertinent geography now spreads over miles instead of blocks. Mixed age/cost buildings are still important, but over a much larger area. Harsh zoning and permitting can limit commercial space availability, increasing scarcity and prices and driving out lower value uses, thus limiting commercial diversity (see yesterday's post on Opportunity City vs. Pleasantville). Density still matters somewhat, but far less than before. Generally speaking, in Jane's world, mobility is relatively fixed and slow (walking, transit), but density is variable - therefore the key to vibrancy is to pump up density. In the car-based city, density tends to stay in a reasonably narrow and low range because of the need to accommodate cars and parking - plus consumer preferences for stand-alone homes - but mobility is variable: average trip speed is very dependent on the availability of high-capacity, smoothly-running arterials and freeways. I would go so far as to call the freeway the "short block" of the car-based city because of its similar relative improvement to the size of the mobility/draw zone.

So the four tenets of vibrancy transformed for the car-based city get reduced to two:

1. Loose zoning/permitting constraints to enable both a wide diversity of businesses as well as population density where there is consumer demand (apartments, condos, townhomes)
2. Maximized mobility with a well-designed, high-capacity arterial and freeway network

These two principles maximize the population within the largest possible mobility/draw zone, which gives vibrancy its best chance of reaching critical mass and flourishing.

All of this is not to say that car-based cities like Houston don't need mixed-use, walkable neighborhoods - but they're not required for us to be a vibrant city/metro. A "nice-to-have" amenity, if you will. What's going on in downtown, uptown, midtown, and The Village (among others) are good, healthy developments - and I think Jane would approve - but they're not the end-all/be-all of vibrancy.

Tomorrow, we'll go into more depth on density vs. mobility by comparing Manhattan and Houston trip scenarios, and what that means for vibrancy, "suburban monotony", frontage/feeder roads, and Jane Jacobs' "dead zones".

[This article was originally published by Houston Strategies.]