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Thu, 11 Nov 2010
This is a continuation of the previous post on Evidence-Based Urban Planning.
The first task of an evidence-based plan is to set objectives. But the types of objectives that go into these plans have to be re-examined. I donít mean that the objectives themselves have to be evidence-based. By and large in a democratic society it is a political process that should be setting objectives. But there is also a great tendency in a democratic process to confuse the objectives with the means of achieving them. If the stated objective is to build more roads when the actual intent is to reduce congestion, or to build more shelters when the intent is to reduce homelessness, then the objectives themselves are the wrong ones. Planners will have to comply with the stated objectives, but without any expectation that they are solving any problem.
What is required is to step back. Is "increasing density" an end in itself, or is it a presumed means of achieving some other end? The technique to use is one that has been invented by every 3-year old, the endless question "why?". Itís a simple epistemological quest for root causes, and itís a question we donít ask nearly enough. Why do you want to increase density? Is it because you believe that it reduces vehicle use, that it reduces the cost of providing services, that it preserves farmland, etc? In that case maybe those are ends in themselves, and density may just be a presumed means to an end. Maybe there are other ways of achieving the same objectives either instead of, or in addition to, what you originally thought. Maybe some other measure that will be taken in order to achieve some other objective will increase vehicle use or increase the cost of services, in which case you may have cancelled out all beneficial effects for lack of defining them as objectives.
The objectives that are chosen must be measurable and to some degree predictable. There is no point in having a plan if no one can tell whether its objectives were achieved. For instance if you are going to do a CPTED analysis (one of the better existing uses of evidence-based planning) to inform urban design, you have to not only be able to measure crime rates before and after, but you have to be able to predict what the crime rate would have been if the design changes had not been applied. The objectives have to be specific enough that they can be measured with some certainty, and that they can be predicted with some certainty, so that five years later you can say that without these design changes the crime rate would have gone down by x% but after these changes it went down by y%. These predictions have to be more than guesswork and extrapolation of current trends. Think for a second. Your hypothesis is that urban design changes will change crime rate. Does your predictive method agree? If your predictive method is insensitive to these design features, then the prediction that you intend to relying on to evaluate your plan will give the same result for the scenario with those features and without, that is to say that it predicts that the design will have no effect.
The other desirable property of the objectives is that they can be achieved in large part through urban planning or urban design. For instance some studies show a strong link between urban form and childhood obesity. Other studies donít. However, all of them agree that many other factors are also involved, including nutritional, educational, social, health, family life, and so on. Itís an important enough issue that public health and educational authorities are also tackling the problem from their end. That makes the objective a difficult one to evaluate in an evidence-based planning framework. The attribution problem, determining whether changes in urban form were the ones that had a major contribution on outcomes or a minor one, is very challenging. That means that this type of objective, although laudable and important, doesnít lend itself well to an evidence-based approach. That is not to say that it shouldnít be attempted. It can benefit from some other aspects of an evidence-based approach, but an objective that suffers from an acute attribution problem may not be the one you want in your plan. Perhaps a more limited objective, like the distances walked and biked or the percentage who walk or bike would be more appropriate, even though they are not ends in themselves, because they are a sub-objective that can be tackled mostly through planning.
Finally, the objectives must be politically legitimate. There are laws that govern what planning authorities are allowed to regulate and I assume that those are respected. But there are also predictable side-effects of certain patterns of development that must be made clear and avoided, like racial segregation, limiting of freedom of movement and freedom of assembly, and impacts on the most vulnerable. There is a moral imperative to ensure these impacts are well understood. But it is all too easy to obscure the true meaning of what is being planned in the belief that elected officials or community members would be less or more willing to support it with partial or misleading information. That is why loaded words must be carefully defined so that they donít mean different things to different people. To some "density" means highrises and to others it means duplexes, while many assume that you're only talking about downtown. Will some be surprised when they find out the implications of the plan after it has been passed? What is meant by "infill", by "mixed use", by "scattered site housing", by "community involvement", by "range of housing types"? Clear communication is required at the time of setting objectives for these objectives to be politically legitimate.
Tags: Urban PlanningSun, 07 Nov 2010
My short piece on evidence-based urban planning in Planetizen seems to have made a liar out of me.† When I first started writing it, there really were only 4 hits for "evidence-based urban planning".† Now there are dozens, a lot of them referring to the article.
The piece hit a bit of a nerve.† I've received plenty of e-mail and some phone calls and twitter.† The majority of them were planners or activists saying they agree with me and that evidence shows that their opinion is right.† For many, all it takes is one figure in one table in an article on the internet, and they have evidence.† Let me help you:
You can cite this article.† I peer-reviewed it myself.
There were some who thought that I agreed with them when I stated that this or that belief does not have enough evidence to support it.† Just because there is not enough evidence does not prove that a belief is wrong, and it certainly does not prove that the opposite is right.
The scarcity of reliable and generalizable evidence does hamper urban planning, but so does the professionís difficulty in dealing with evidence.† I mentioned the political aspects and the complexity of interactions in the Planetizen piece, but even when evidence exists, using it may go against the grain.† To be clear, evidence does not mean one study about one building even if itís in Portland.† It means a systematic review of all available research to find reproducible results that are likely to apply in similar situations.
In "Is There a Role for Evidence-Based Practice in Urban Planning and Policy?", Planning Theory & Practice, Vol. 10, No. 4, 459Ė478, Krizek, Forsyth, and Slotterback †note that politicians given access to systematic†reviews of all research on a topic will tend to ignore it except to justify decisions after they are made.† Planners given access to this information will pass on only the result that corresponds to their own belief.† In the "Design For Health" project, many communities were provided with easily accessible systematic reviews of research on the relationships between urban design and health, and funded to integrate this evidence into their process.†† Many planners had difficulty doing so, and either picked single studies that supported their earlier position, or simply added the words "health" or "healthy" without any change to the planning strategy.
As the authors note, "... too often a suggested policy action is justified with reference to a single source of evidence that fits the practitioner's or author's preconception. Cases, anecdotes, or even research studies are cherry-picked to fit a situation or idea. This is perhaps the biggest current problem with the use of research evidence: when practitioners use only a single source, unworried by conflicting evidence because they ignore evidence that does not agree with their position. As one reviewer commented, several approaches to planning that claim to be evidence-based have a very thin base of evidence which is used to justify pre-existing positions."
The direct use of evidence may well work for local, small-area planning decisions, but for city-wide effects like transportation or land use planning, given the complexity and interactions of different components of a city, I don't know how anyone can make decisions without modeling the city with different scenarios.† I am a big fan of UrbanSim and similar models, as some may have noticed.† A city is like a balloon.† Squeeze it in one place and it will bulge somewhere else.† Even when you do find statistically significant relationships between, say, some aspect of density and some aspect of vehicle use, there is so much scatter in the graph that most cities are not on the fit line. They could invest massively in following the scientific evidence without any benefit.† There are few typical cities.† Directly applying the evidence won't work, other differences between cities may well overcome the desired effect or make it work in a different way. To me, it's clear that research knowledge and local knowledge must be combined, and the proper way to combine them is to use a model that is sufficiently fine-grained to be predictive.
The interpretation of data in the planning literature and in the activist community, as well as among planners, is filled with well-intentioned errors.†† Self-selection bias is a common one Ė measuring behaviour in a group without realizing that this group's membership does not behave like the rest of the population.† Presumed linear relationships are very common, the untested belief that doubling a cause will double a result, as is the presumption of linear independence, that two causes together will have the sum of the effects of the two taken separately.†Mistaking proxies for the actual variables, and chaining together proxies of proxies is also very common. All of these sometimes add up to a mistaken belief in additivity, that the sum of local effects will result in a global effect if repeated.† Add to this the chorus of voices that firmly believe in their own interpretation of data and planners are left with the complex job of explaining statistics to the unwilling.
The role of evidence-based urban planning practice has four major facets, which will be described in the next blog posts.† But here is a preview
Tags: Urban PlanningFri, 18 Dec 2009
Amidst the gloom of climate change talks in Copenhagen not living up to their potential, there is a possible solution to the current lack of agreement. Although it's usually presented as a bad thing, border adjustments could help the world out of the current impasse.
Some countries, like Europe, want to move more aggressively than some other countries, but less so than yet other countries would like them to move. Some, like the US and Canada, will only agree to binding aggressive targets if other countries like China and Brazil have such targets. No one will move unless everyone else moves first, and unless others are bound to greater reductions than the other believes is their fair share. The reason, purportedly, is trade. It is unfair to have carbon restrictions, which drive up the price of our exports, unless our competitors have similar restrictions. So countries will not even bind themselves to the less-than-fair share that they are willing to accept unless everyone else agrees to a more-than-fair share.
This is an impasse that can relatively easily be resolved with border adjustments. The US, France, and Germany, among others, have draft laws ready to go that allow them to charge border adjustments. Say that your country has carbon pricing such as cap-and-trade or a carbon tax. Every product that you produce for internal consumption has had to pay a fee proportional to the amount of carbon emitted to produce it and to produce its inputs. If you were to allow duty-free imports of similar products from a foreign country that didn't have carbon pricing, it would have an unfair advantage. Border adjustments let you charge the carbon fee at the border. That way, the fact that this country does not charge for emitting carbon no longer gives it an unfair advantage.
This solution is imperfect, of course, but it does get past the "you first" impasse. It doesn't matter, for trade relations, if a foreign country doesn't agree to reductions. As long as we and our trading partners have border adjustments, that doesn't help them compete unfairly. Not only that, but we're the ones that keep the money from taxing the carbon content of their product, not them. That should be an incentive for them to set up their own carbon tax program.
The problem is how much? How do you know how much CO2 is emitted in the supply chain leading to the production of each product? How much do you charge per tonne? The amount that it costs on your domestic market or the amount that would need to be charged in the producing country to have an equivalent effect? And what would be an equivalent effect? The per-capita emissions of the UK are half of the per-capita emissions of Canada or the US. UK workers drive less and buy more local food. If they don't happen to implement a carbon price, they're still emitting less than us. Would we charge them the same carbon price as, say, Spain or Italy whose emissions are rising out of control?
So what it comes down to is a solution that lets each country cut unilaterally without worrying about unfair competition, and that encourages reluctant countries to act in the interests of the world, even if they are only driven by self-interest. I wouldn't worry too much about finding the correct price for border adjustments. They should only be a transitional measure while waiting for the more reluctant countries to join in.Mon, 30 Nov 2009
Up until yesterday, I thought that democratic control of urban planning issues was a generally good thing. Sure, there was Oregon's Ballot Measure 37, where a well funded advertising campaign convinced voters that zoning to restrict development potential was theft by the government, but the subsequent vote on Measure 49 reversed the worst of it.
The Sierra CLub and others worked pretty hard to get Floridians to vote on a measure that can give the population a veto on major amendments to Comprehensive Plans. By and large as far as I can tell, voters tend to vote for reasonable, environmentally sound and tolerant policies, it's not just NIMBY.
But then came the shocking national Swiss referendum on the building of minarets. The proposal to add this clause to the Swiss constitution "The construction of minarets is prohibited" has now passed. This was done despite virtually all Swiss governments and religious leaders urging the population to vote against it. This gives democracy a bad name. At the very least it gives Swiss citizens a completely different image. Neutral no more.
I live in an area of my city with a fair number of muslims and there is a small mosque on the second floor of a building. The ground floor has 8 businesses and I would guess that 3-4 have muslim owners. I was eating in an ethnic restaurant there and heard a faint call to prayer from a speaker inside the restaurant. It was quite lovely. I wondered why the speaker wasn't outside. I wrote a short piece in the local community paper. I was surprised to see that many of my neighbours hoped that noise by-laws would forbid it. In any case the mosque had no intention to even ask. Maybe most people aren't as happy as I am to see freedom of religion in practice.
Thu, 01 Oct 2009
Have a look at this scene. Where would you guess it is? Click on the square at the upper right corner for a larger view.
Now go see it on Google Maps. and zoom out and out and out. Surprised?
Welcome to the new reality. It's time to start over.
Wed, 16 Sep 2009
Based on a book review of Green Metropolis by David Owen and an earlier New Yorker article by the same author, there is still a great deal of confusion about the effect of localized density on energy use. Everyone should live in Manhattan says the author, who apparently lives in Manhattan. New Yorkers use the least energy of anyone. Did you notice the old switcheroo? Manhattan and New York briefly became synonymous.
Let's sort out the fact from the fiction. The book claims that living in highrises in Manhattan makes you use less heat, because of shared walls. Is that true? No. Heating and cooling highrises in fact uses a lot more energy per square metre and per person than heating and cooling any other sort of building including single family homes, and the total energy requirement is also greater. The average household in Manhattan is much smaller than the average household elsewhere, so Manhattan apartments tend to be a lot smaller than houses elsewhere. To its credit, Manhattan has a wonderfully efficient community heating system where steam produced in part as a byproduct of electricity generation is piped to buildings to be used for heat.
The book's specious argument about elevators is a bit silly. They say it take less energy to move people horizontally than vertically. Per metre when doing it mechanically, perhaps. But when you want to move people 15 metres away vertically you build an elevator. To do this horizontally you expend no energy at all, you expect them to walk, and more often than not you will not provide them with a lit, heated, cooled, maintained, stainless steel construction within concrete. Unless they take the subway, which probably requires even less energy.
New Yorkers in general use a lot of public transit. This proves in part that people are more likely to take a subway when there is a subway than when there is none. New York is different from most other cities in the US. In research I did a few years back when I tried to see the relation between density, household type and transit use, New York City was off the charts for just about everything. Everyone there takes the subway whether they are in high or low density. You have to remember that Manhattan is only a small part of New York City. Most of the city is not highrises, a lot of the area of New York City is made up of medium density single family houses. I lived in one in Queens and commuted to Manhattan every day. People in medium density in New York take the subway practically as much as people who live in Manhattan highrises. You have to be careful in your assumptions. A large proportion of Manhattan is not highrises and outside Manhattan the vast majority of residential buildings are ground-oriented. But New York has great public transit even in densities where other cities would not have a subway, so lower-density New Yorkers use it.
To me, it is the transit use by lower-density family-oriented areas outside Manhattan that is the great success of New York City. The two populations are very different. Take a typical apartment dweller in a highrise in Manhattan and move him to a lower-density area still in roughly the same size apartment. Is he driving more? Probably not very much. Now take a family of four or five in Queens and move them to lower density. How much will they drive then? A whole lot more. The lower-density area they have moved to will probably not be walkable at all and with 2 jobs and a few kids, that family has very high transportation needs.
It happens that in New York City, the highest population density areas are made up of highrises. But that is not the case in other cities. So, for instance, while Manhattan with its highrises has a population density of 27,000 people/km2, the Eixample area of Barcelona has a density of over 35,000 people/km2, and it does it almost entirely with attractive 5-6 storey buildings (see picture). Many areas of San Francisco do the same thing. Plateau Mont-Royal in Montreal is over 12,000 people/km2 with mostly 2-storey and some 3-4 storey buildings. You really don't need highrises to get population density. What you do need is units that appeal to households with children; that way you get a lot more people for the same number of units.
New York and other cities with dense cores and a high gradient between high-density centres and lower-density rings have polarized their population between the small households who are in the high density and the larger households who go further and further away. Having a Manhattan means that you will also have an extended metropolitan area of commuters spread across several states. When you count the total area and the total population density of this tentacled monster, the Greater New York area, which is a direct result of Manhattan's land use, doesn't look so good. This is a general rule in North America. The denser the core the greater the sprawl, and it gets worse every year. New York's population has not been growing, but its area has. Within New York City, population suddenly stopped growing in 1961 when zoning was changed to allow high density just about everywhere. Then earlier this decade in the "downzoning uprising", with Green Party people behind the movement, zoning was changed downward and lo and behold the population and population density started growing again for the first time in over 40 years.
Whether in Manhattan or in Portland, you can't just look at localized density and think you're making progress. When you change the distribution of the demographics you don't improve energy use as a whole. If you build up a small area you could get very good stats in that one area, as people who are already prone to taking transit move there and continue taking transit. But what happens to the other demographics who get displaced? What about the ones that don't want to live within a few blocks of a high-density hub and who see the area becoming less family-friendly. You may have just moved them away from a transit route to an area where their energy use will skyrocket.
It's a complex topic and the easy answers, like why can't everyone do what I do, simply don't work. It's a shame that people spend their time promoting simplistic solutions and attacking the simplistic solutions of other, rather than simply pricing carbon and letting our economic system minimize total emissions using the price signal.Mon, 24 Aug 2009
Knowing the Guardian newspaper, it's not very surprising that they would jump on a story where an architect is angry at Prince Charles, but they have been at it now for over two months. Two months ago, Charles had a discussion with fellow royals from the Qatari royal family who own some land in a prime location in London, near one of Sir Christopher Wren's achitectural masterpieces. Unsurprisingly, his opinion, as always, was that in architectural heritage areas a more traditional style is appropriate. They decided he was right, and withdrew the design, much to the fury of architect Richard Rogers, who went to the newspapers demanding that the Prince be forbidden from speaking to other landowners.
In a small sample of this week's set of attacks. the Guardian again attacks Charles, this time for having spoken to another developer who wanted to build a different modernist building near a different one of Sir Christopher Wren's achitectural masterpieces. Again, they call upon constitutional arguments to silence him. Whereas the constitution guarantees the right of free expression for most people, arguably it limits this right for a few members of the royal family, and the Guardian is quite keen to use it to muzzle opposing points of view.
In this and previous cases (usually modernist high-rises adjacent to Wren buildings) Charles has never made use of his constitutional role, that is to say has not tried to intervene with the national government or its ministers. Charles himself is a landowner and property developer, and has dealt with a large number of architects. He does not dabble, he "puts his money where his mouth is" and develops properties that he owns using traditional architectural styles. These properties are quite profitable, as it turns out.
The Guardian criticizes him because Charles is in a position to wield his influence on a lot of land owned in part by the royal family. They are attacking him for his role as a landowner and developer who has undue influence on development of his own land. How socialist of them. I don't see them going after other developers for occasionally commenting in private to other developers. In this area, the prince has no actual influence. There is no penalty for ignoring him, in fact in latest case that the Guardian uncovered, the developer did exactly that and the architectural monstrosity was built.
On balance, the influence of Prince Charles has been positive. Precisely because he is not starstruck by the knighted and decorated superstars of the architectural upper class, he speaks his mind openly about those things he cares about and yet seems to studiously avoid using his constitutional role. What he uses is his occasional invitations to speak on the subject, his own land, and the charitable foundations that he has started and staffed with experts. He started talking about sustainability before it was mainstream. He looked for ways to improve density and walkability within a traditional context when everyone else thought this was old hat and before it became the rage. On the few occasions when he has come out against specific projects, they were truly dreadful and badly located. He used to do it publicly and was criticized for it. He now does it privately, and is criticized for it, or in public when he is invited to do so, and is criticized for that too. I think that starchitects just don't like to have their work questioned. And they particularly don't like losing business to upstart traditionalist architects that they have spent their student years and career belittling.