14.4.11

Comparing the Small Blocks of the Midwest and the Northwest

Curiously, Jane Jacobs devotes a chapter of The Death and Life of Great American Cities to a relatively obscure topic: the “need for small blocks” in cities. Using Manhattan’s Upper West and Upper East sides as examples, Jacobs argues that long blocks make for “self-isolating streets” that restrict pedestrian choice and curtail economic activity throughout urban neighborhoods.

Jacobs’ small block advice crossed my mind on a recent trip to Portland, Oregon. At first glance, my hometown of Minneapolis has a lot of similarities with Portland, particularly in its housing stock, age of development, density and mixed-use characteristics. Yet many older neighborhoods in the Pacific Northwest have smaller block sizes that you will find in the Midwest. For example, the average block size in Southeast Portland or Seattle’s Capital Hill neighborhood is less than 100 meters square, whereas most of the blocks in South Minneapolis or Chicago’s North Side are nearly twice as large. While walking through any of these neighborhoods, block size is not necessarily something you might notice, I think that the size difference has a few subtle effects.

In these cities, block size seems to affect traffic calming and walkability. In other words, the size of city blocks impacts the degree of pedestrian accessibility and choice. Smaller blocks increase the ratio of public street to private developed space, and create a “finer mesh circulation pattern” in urban neighborhoods (Siksna 1997). For example, Seattle’s Capitol Hill area and Portland’s Southeast neighborhoods suggest how small blocks can lead to walkable urban landscapes. On the other hand, the commercial streets of South Minneapolis, seem to be a bit less pedestrian friendly because of their larger size. With fewer intersections, cars can travel a bit faster. Likewise, there are fewer street corners, so that pedestrians have fewer choices about which path to choose.

Jacobs’ concerns about block size were primarily about the generation of diversity, about how to generate new forms of economic activity. She argued that block size had a large impact on the potential pedestrian populations for businesses, and that smaller block sizes made for more integrated circulation patterns. While Jacobs’ ideas are appropriate for a place like Manhattan, with its contiguous mixed-use fabric, in the streetcar neighborhoods of Seattle, Portland or Minneapolis block size is not really about generating economic activity. Instead, it forms an almost atmospheric part of the urban landscape. It is worth stopping and noticing how these differences in layout have fostered some of the most vibrant neighborhoods in US cities. The Northwest should be grateful for its legacy of small, walkable blocks.

[The relative block size patterns of residential neighborhoods in four cities.]


References:

Jacobs, J. (1961). The Death and Life of Great American Cities. New York: Random House

Siksna, A. (1997). “The effects of block size and form in North American and Australian city centres.” Urban Morphology. 1. Pp. 19 – 33.

10 comments:

Anonymous said...

Who would have tought that this blog would be advocating MORE streets for cars to drive on.

Bill Lindeke said...

LOL

Mulad said...

Block size is pretty important, and I often wish Minneapolis and Saint Paul had smaller block sizes in most areas. I definitely believe they help the pedestrian experience by creating more routes along which people can wander. There's simply a lot more to discover when the block sizes are small, and traversing a large number of blocks also contributes to a sense of distance, so a city with more blocks to it will seem bigger even if the distance traveled is the same.

The common New Urbanist example of a super-dense grid is Savannah, Georgia. The roads are typically narrow, and some of those streets would be called alleys elsewhere.

On the other hand, Barcelona has blocks which are about 4x the size of Portland blocks -- probably bigger than the ones around here -- and they have a huge number of people crammed into the central part of the city. They do chop off the corners of each block, though, which basically makes every intersection into a plaza -- a pretty interesting idea.

Still, even Barcelona's blocks are tiny compared to what is seen in suburbia/exurbia.

It's certainly not necessary for a city to have super-small blocks, though, but I really think more places should subdivide their blocks using sidewalks and bike paths. How would it feel for a standard Minneapolis block to get divided up into 2, 4, or 6 chunks, each with densely-packed buildings? I think that would be a pretty great thing to see.

I personally think it's also a good idea to add diagonal walkways through blocks when possible. In a gridded city, the walk shed from a point ends up having a diamond shape, but adding diagonal walkways changes that to be more octagonal, and much more like the hypothetical circle that TOD planners like to use.

Of course, each new road and path adds more pavement and takes away from the amount of land that can be developed. We massively under-utilize the land in most parts of the U.S., so I'm not too concerned about the latter, but neighborhoods definitely need to be built so that they can financially sustain the amount of paved surfaces that they have. Minneapolis is Pothole City right now, and they need to get fixed before launching too far into paving more stuff.

Reuben said...

It's been a long time since I've read jacobs. Is she really talking about the differences between block sizes in Minneapolis and Seattle (as opposed to say, Minneapolis and Woodbury)?

Reuben said...

A great case study, by the way, is Salt Lake City, which was originally designed with giant square blocks about 1000' per side. They've spent the past 100 years trying to figure out how to chop those blocks up in half or even quarters. In many cases (especially in residential areas), it's resulted in a lot of land-locked parcels that are only accessible through a strange curvy alley or something.

Alex said...

Good post - one of the things I love about the west end of St Paul are the smaller and inconsistent blocks. Viva le diagonal!

Also have you seen this poster:

http://greatergreaterwashington.org/post/6002/the-variety-of-american-grids/

Anonymous said...

FYI - the satellite picture labeled as Chicago is actually another picture of Seattle (check Salmon Bay Park)...

iserve pharmacy said...

I think that Jane was the best American-Canadian writer and activist with primary interest in communities and urban planning and decay.

Anonymous said...

Does any body have any data of pedestrian and cycling improvement because of block size in Portland and Savannah.
I am looking for good case study for block size versus walk ability
if any one know link for the document or have any document comment on the same

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