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.]
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.