Phoenix’s new TOD districts. From theatlanticcities.com.
I saw this article from Eric Jaffe a few days ago and it sent me on a bit of a journey that I hope you will find interesting. In the article, Jaffe discusses how Phoenix, a city which would not exist if not for massive water projects, cheap housing, and abundant air conditioning, is addressing the fact that nobody wants to ride its fancy light rail train. While light rail projects in Salt Lake City and Denver have been overwhelmingly successful, Phoenix’s venture into improved transit has languished. So the city has organized a series of five districts along the corridor and gotten federal funding to promote transit-oriented development and find out why no one is riding.
There are a couple of reasons. Unfortunately, Phoenix’s light rail line opened in 2008. Yes, that 2008. And boomburgs like Phoenix took the hit even harder than the rest of us (which is partially why Philly was able to take back the number five spot from Phoenix in the largest cities in the US after the 2010 census). But there are deeper-rooted issues that have kept TOD from blossoming like a desert rose, and those are principally density and urban design.
Light rail, although more affordable than a subway or elevated train system, is still quite expensive, and needs a certain concentration of people to be viable. According to John Renne, that magic number is nine dwelling units per acre. As you can see in the above map, very little of Phoenix meets this threshold. While Phoenix does have over 1.4 million people, those folks are sprawled out over more than 500 square miles. I wonder if Phoenix planners were hoping that the light rail system would encourage density to develop along the corridor, but really they should have planned the density in before installing the rail.
The other main issue is that Phoenix is in the middle of the desert, and is quite an unpleasant place to be outside in. And unfortunately, the development patterns of the city have only exacerbated the issue, creating a heat island effect over a huge area. This happened because Phoenix is an entire city designed like a post-war American suburb, which was designed largely for the moderate climates of higher latitudes and not the blistering heat of Maricopa County.
But it’s not like cities have never been built in deserts before. The arid climates of Mexico, Northern Africa, and the Middle East have hosted hundreds of large cities, many larger than Phoenix and some that have been around for thousands of years. But these cities weren’t designed the was Phoenix was, and their adaptations allowed them to beat the desert heat.
The name of the game in desert urban design is shade and wind. After combing through over a hundred cities and comparing them to Phoenix based on climate, World City status, population, location characteristics, and presence of rail transit, I came on two examples which are particularly apt examples: Dubai, UAE and Monterrey, Mexico. Both cities share a climate zone with Phoenix (which stradles the boundary between Hot Desert and Semi-Arid climate classifications), are both World Cities of higher rank than Phoenix, have similar populations (with Dubai at 2.1 million and Monterrey at 1.1 million), both have extensive rail transit systems, and Monterrey shares Phoenix’s interior location (whereas Dubai is on the coast). Let’s take a look at these cities and see what Phoenix can learn.
Dubai is an Medieval Arabian seaport. Whereas many Arab/Muslim cities are built around a dense medina, where the widest streets are often only spacious enough to accommodate two passing camels, Dubai, which up until recently had more money than you could shake all the sticks at, adapted its center, building larger buildings and a system of streets that serve cars while still allowing for pedestrian paths within blocks. The tall buildings and narrow passageways create shade which is intensified in some areas by souks, or covered pathways, which often are a gathering place of commercial activity. Many of the buildings are also light neutrals in color, which helps to reflect heat, rather than absorb it like dark materials, such as asphalt.
Monterrey is a Mexican city of Spanish imperial origin, and as such its urban design was based on the Law of the Indies, which allowed for rapid expansion in a roughly gridiron pattern. While not as tortuous as the Arabian medina, the streets of Monterrey are relatively narrow, and the buildings make extensive use of awnings, window covers, and other shade devices, while the public realm is full of trees and shade structures.
While both of these cities feature some large roads with high-speed traffic, these streets are the norm in Phoenix, even along the light rail line. Most of the roads it parallels have four or six lanes of traffic, and widen at corners with dedicated turning lanes. In many cases, buildings along the roads are set back behind a parking lot. There are even numerous vacant lots along the rail line. These conditions need to change.
First, narrow everything up as much as possible. Remove the buffers around the trains and let cars come right up next to the curbs. These buffers are “necessary” when you have high-speed traffic, but that’s the last thing you want on a pedestrian/transit corridor. Additionally, remove the dedicated turn lanes at intersections. They are there to make life easier for cars, and increase the distance and time necessary for pedestrians to cross the street. Screw the cars. Put the pedestrians first. Next, narrow the travel lanes to ten feet, and never have more than four. Again, this road is for pedestrians and transit users, not cars. Include a row of on-street parking, which buffers pedestrians from traffic and further encourages drivers to slow down. Include buffered bike lanes on the outside of the parking lane, so cyclists don’t have to compete with cars and can avoid being doored. Provide shade on the sidewalk with either low-maintenance shade structures or trees (I personally love the local Palo Verde trees). Bring the buildings right up to the sidewalk, and put the parking behind. In these areas, you want people to be able to see your storefront window, not your ample free parking.
Now that we’ve scrunched everything together, it’s time to go up. Buildings should be, at the very least, two stories, to allow for vertical mixed uses. When it comes to creating a sense of enclosure on a street, the bare minimum ratio of height to street width is 1:6. 1:2 is better. 1:1 is probably best. Beyond that you start getting into the enclosure territory that only a New Yorker can love.
Building height can also be manipulated to create microclimates and cool an area down. For instance, if you have taller buildings on the south side of a street, the shadow they cast to the north will keep the street cooler. Since Phoenix is at the fairly low latitude of 33.5 degrees north, the sun is only ten degrees south of directly overhead in the summer. So to create shadows, especially across a wide street, you need some really tall buildings. Of course, if you narrow the street, you can get by with smaller ones. Tall buildings on one side of a street can also catch winds and force them to ground level. Since the prevailing winds in Phoenix blow pretty much due east, putting tall buildings on the east side of north-south running streets would be the best way to catch and divert wind.
Finally, architectural details can do a lot to make being in Phoenix more pleasant. Make extensive use of awnings and other shade structures, as even small Casa Grande has done in their downtown. Although you want a lot of visible glass on the ground floor for stores, consider screens and shades for upper floors. Make sure windows can open to allow for natural ventilation. The principle colors of a building should be low albedo, to avoid heat gain, but that doesn’t mean bright colors can’t be used for accents.
Phoenix’s light rail has a lot of things going against it right now, but if the city can learn something from its desert ancestors and take advantage of density and urban design, then they can create a wonderful transit-oriented corridor that will breathe new life into the city.
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