Height is not the only factor that determines how dense a city is. Width -- namely, street width -- matters just as much. It just happens that street width is more difficult to change (politically, if not technically). When density advocates argue in favor of removing height limits and building skyscrapers, we are playing a game that is rigged against us. What we really want (or at least, what I really want) is not to increase the scale at which our cities are built, but to reduce it: to build cities that are sized for humans, rather than for the giant fast-moving cages that we so often surround ourselves with. We correctly recognize that the aspect ratio of our cities is out of whack, creating far too much distance for the amount of place in between. But we propose to solve the problem by enlarging one dimension, when we should be shrinking the other. What if your motivation is not urban form, but economics? Wont you get the cheapest housing if you allow every single plot of land to be built as densely as possible? Perhaps this is true, in a fantasy world where Kowloon Walled City is universally hailed as a paragon of urban design. In our world, there are many factors limiting how tall you can build, ranging from structural engineering (e.g. depth to bedrock, or intervening subterranean uses), to light and view corridors, to elevator and egress design, to local politics. Manhattan is an alpha city, and for a number of reasons, it can get away with taller buildings than you might find elsewhere. A more representative example might be Portland, OR, a mid-sized city that has the basic form of a modern North American city, but has nevertheless gone to great lengths to make itself walkable. (Note that by modern, I mean a city that was settled in the 19th century or later. Settlements that significant predate that time period, like Lower Manhattan or Bostons North End or the Old City in Philadelphia, already have the shape that I think we should be aiming for.) Downtown Portland has a complex zoning system. Some lots have maximum floor area ratios, while other lots have maximum heights. For the sake of argument, well assume an average floor area ratio (FAR) of 6. Note that this doesnt mean a 6-story height limit. For example, much of downtown Vancouver (BC) has a maximum FAR of 6, but its full of buildings with short podiums and tall, thin towers. This building design feels less imposing at the street level than a 6-story slab, but contains just as much usable space. Realistically, in a mid-tier city like Portland, youre not going to find a large area with an average FAR much higher than 6. People just arent going to tolerate that many tall buildings. A Portland city block has 200 feet square of buildable space, and its surrounded by streets that are 64 feet wide. (These numbers were presumably chosen so that exactly 20 of those 264-foot blocks would fit in a mile, which is a terrible way to design a city, but thats neither here nor there.) When you factor in street coverage, a per-lot FAR of 6 leads to a total FAR of about 3.44. Already, something should seem amiss. Were building towers that are hundreds of feet tall, and yet when you factor in street width, the total usable space is less than a 4-story building (without the streets). What gives? Lets modify the example a bit. Well shorten the buildings to a mere 4 stories (with 100% lot coverage), and well narrow the streets to a mere 15 feet wide. This is on the tall side for a traditional city, but there are a lot more people in the world now, and elevators didnt exist back then. Factoring in street coverage, our new per-lot FAR of 4 turns into a total FAR of ... 3.46. Tall buildings demand wide streets. Even if people were willing to tolerate walking around in near-darkness, you need enough room for everyone to walk around. But what do you get when you combine tall buildings with the street widths they require? You get a city that isnt any denser than the ones weve been building for hundreds/thousands of years. Its just a lot more expensive, a lot more controversial, and a lot harder to get around. I chose Portland as an example because it has some of the smallest blocks (200 feet square) and arterial streets (64 feet from building to building) of any modern American city. So if my argument works for Portland, then it also works for other American cities, which tend to have much larger streets and correspondingly less ground coverage. The urbanist movement has spent decades trying to convince the public that their instincts are wrong, and that height is not their enemy. In this respect, I believe that we are committing the same sins as Le Corbusier and Robert Moses before us. Human intuition is our friend, not our enemy. For centuries, people understood that cities should be easy to move about, and so they built medium-height buildings in very close proximity. When cars came around, people understood that walking next to cars is unpleasant, so they built freeways (to get cars away from people), and shopping malls and cul-de-sacs (to get people away from cars). Now, people are starting to realize the problems with freeways and shopping malls and cul-de-sacs, and so theyre starting to look for solutions. All this time, people have understood the appeal of relatively quiet streets (meaning few motor vehicles), and of relatively short buildings. What these people want is not wrong. In fact, its a lot closer to right -- to a traditional city -- than what weve been trying to sell them. The average Seattle residential street might as well be a pedestrian zone, for the amount of car traffic that it gets. You could cut the street width in half, and no one would complain. (In fact, there are streets where the city has done exactly that: https://goo.gl/maps/VRrhS) The only thing missing is commerce, and that problem is almost trivial to fix. Buy a corner lot; ask the city to vacate half of the street width; build a 3-story building to the lot line, with a few small shops below, and apartments above. Voila: youve just turned your residential neighborhood into the beginning of a traditional city. Of course, real life is never so trivial. Many people fear change, of any sort. People will complain about losing the street width they never use; about losing the two potential parking spots, even though the street is never full; about the shoppers who will drive to the business and steal their spots (i.e. the city-owned spots that happen to be in front of their homes). But honestly, I would much prefer to be fighting those battles. If we had spent the past 10-20 years trying to convince people why on-street parking is a waste of valuable urban real estate, or why streets are too wide, or how commerce can peacefully coexist with quiet residential uses, we would have gotten somewhere by now. Instead, weve succeeded in building places like University Village, which is what you get when a shopping mall developer tries to replicate Florence with a paint-by-number kit, and like South Lake Union (SLU), which could be a walkers paradise except for being completely surrounded by cars going 40 mph. There are some people who love living in places like SLU, and I think thats great. But I challenge you to stand at the corner of Westlake and Mercer and tell me that youre gazing at a walkers paradise. Is that really our best answer to suburban sprawl? Is that really what we want the world to look like? And if not -- and I certainly hope not -- then why arent we arguing for what we really want?
Posted on: Tue, 23 Dec 2014 06:29:10 +0000
Trending Topics
Recently Viewed Topics
© 2015