Tuesday, May 25

Variety of American Grids

I wanted a nerdy planning-related poster for my wall (other than the periodic table of city planning), so I made one this week. I scoured Google Earth and measured that quintessentially American grid in about fifty downtowns around the country. Of course, there are variations in block proportions within downtowns, but I tried to pick cities that had more uniformity than average to come up with a single prototype. Here's an image of it, or shoot me an email if you want a poster-quality version. (I personally don't have the web space for it right now).


Exploring these grid proportions messed with my preconceptions. I assumed the more western and newer cities would have larger grids than the more eastern and older cities, but no obvious pattern is discernible to me. Mobile, AL, settled by French colonists in the early 18th century, Tulsa, OK, a 19th century farming town, and Anchorage, AK, a 20th century frontier town, all share the same 300' x 300' internal block (street widths vary a little). What compelled the early settlers of these towns to choose, say, 220' over 440' lengths? I can't say I have any idea right now.

Manhattan is also a curious story. According to Witold Rybczynski, the expanding nation unequivocally chose the 1811 Commissioner's Grid of New York City over L'Enfant's baroque-influenced plan for Washington, DC as the model for new towns. While this is surely true, it begs the question: why are New York's long and skinny blocks not found anywhere else in the country? You would think at least one group of western settlers would seek to emulate their home town of New York more exactly.

I'm leaving aside the interesting value questions around block size. Ever since Jacobs, conventional wisdom has held that smaller blocks are preferable for walkability, but urban designer Fannis Grammenos challenges this somewhat in a recent Planetizen post.

12 comments:

Anonymous said...

Gotta ask, where is Philly/Raleigh on this chart?

Daniel said...

I regret leaving Philly off of this, because it's the classic gridded city. But I couldn't really find any standard that I could single out. Things have been sliced and realigned so much over the years. I think Penn's original was something like 400' by 500' for internal blocks, putting it on the large size in this illustration.

Raleigh is 420' x 420' for internal blocks with 70' ROW. Pretty big too.

David said...

Is it any wonder, then, that the fates of Houston, TX and Sheridan, WY are so inextricably linked?

Benjamin Hemric said...

Thanks for the very interesting post!

I'm surprised though that you didn't include Chicago's grid. Although I've never been to Chicago, it seems everyone I've ever spoken to has nice things to say about Chicago's downtown. And although these people rarely mentioned the street grid itself, reading between the lines it's always seemed to me that the grid may be at least partially responsible for their positive feelings.

A few other points:

1) As your post seems to hint, Manhattan actually has a number of different grids. The blocks of SoHo and the South Village, for instance, are long in a north-south direction, rather than an east-west one.

2) And even within the 1811 Commissioner's Plan, the blocks west of Fifth Avenue have very different proportions than the blocks to the east of Fifth Avenue. (Plus even the long blocks west of Fifth Avenue are not uniformly long. The blocks between Fifth and Sixth are longest and thus longer than the blocks between Sixth and Seventh, for instance.)

I don't know why the east side blocks were made shorter than the west side ones.

3) One important consequence of the fact that the east side bocks are shorter than the west side ones, is that this forms a kind of natural experiment of sorts (just the way Philadelphia's four Center City parks form a kind of natural experiment). And just as with Philadelphia's Center City parks, Jane Jacobs doesn't let the natural experiment go to waste. She points out how the short blocks of the east side seem to be greater generators of diversity and urban resiliency (and urban health) than the long blocks of the west side.

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Daniel wrote:

Manhattan is also a curious story. According to Witold Rybczynski, the expanding nation unequivocally chose the 1811 Commissioner's Grid of New York City over L'Enfant's baroque-influenced plan for Washington, DC as the model for new towns. While this is surely true, it begs the question: why are New York's long and skinny blocks not found anywhere else in the country?

Benjamin writes:

A) Don't know how true this really is, but supposedly NYC narow north-south blocks and sometimes long east-west blocks are due to the idea that it would be desireable to have many (narrow) streets connecting the two "rivers" and only a few (relatively wide) streets running up and down the island. If that's true, then the mindset of the time might have been such that other places choosing a Manhattan-like grid may have figured that they dldn't very frequent east-west streets because they didn't have the same situation that Manhattan did.

B) I used to think that Manhattan's very long blocks were kind of unique -- and maybe they are rather rare -- but there are other examples.

One that I recently came across is Toronto -- which seems to a "basic" grid with even longer blocks than Manhattan (with some of the long blocks in the downtown area appearing to have been split up at one time -- although don't know if this is really true in fact).

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Daniel wrote:

I'm leaving aside the interesting value questions around block size. Ever since Jacobs, conventional wisdom has held that smaller blocks are preferable for walkability, but urban designer Fannis Grammenos challenges this somewhat in a recent Planetizen post.

Benjamin writes:

Although short blocks certainly seem more walkable than long ones, I'm not sure if the term "walkability" really fully captures the benefits that Jacobs sees in short blocks.

From a quick reading of Fannis Grammenos' post, though, I don't see where he is challenging the preferablity of small blocks for "walkability" -- which seems to me to be something that is hard to challenge.

-- Benjamin Hemric
May 25, 2010, 8:38 p.m.

LH said...

Daniel - Very cool. Would make for a cool poster, agreed.

Re: Manhattan, not quite the same thing but I was told that the tiny island of Tinian in the Commonwealth of Northern Marianas Islands was laid out by planners from NYC; there are no named streets except for one that cuts right through the whole island, which is named . . . Broadway.

Daniel said...

LH, that is pretty funny - some ambition from the folks in Northern Marianas Islands.

Benjamin, I do have a couple of diagrams for Chicago but never ended up including them in the poster. There is a distinct difference between block sizes north and south of the river in Chicago's downtown.

You're right that Grammenos is considering the grid on more general terms than just walkability, mostly the amount of land dedicated to public right-of-way and the lack of variation in sight lines. It's probably more accurate to say that he sees these as overriding any walkability benefits to smaller blocks - although he doesn't really address this directly.

And I didn't know that the east side of Manhattan has shorter blocks than the west. That really is like a controlled experiment - an urbanist's version of a psychologist's twin study.

Eric Orozco said...

Interesting that Carson City has a tighter grid than Portland's... What's with all this talk we hear on the blogosphere about Portland's being the "densest" grid in America in terms of intersections, then? :)

That Grammenos article puts Portland's grid at 360 intersections per square mile. Well, if that is the case, Savannah's grid, uhm, has also been ignored in the determination of "densest grid".

Not that I aspire to the knock Portland off any pedestal. ') I think Savannah planners, good southern folk that they are, are just too darn polite to pipe up.

But I was raised a Texan (the other kind of southerner) so I'll point it out for them: Savannah's grid has 400 intersections in a square mile (525 if you count the intersections of the service alleys with the grid - which are part of the public right-of-way grid). Because the historic district is smaller than a square mile, the grid density, if you use 1/4 mile sample within the historic district, is actually higher than that (640/sq.mi. ...800/sq. mi. counting the alleys).

Savannah's grid is so dense in fact, that it represents a "composite grid" with two grids superimposed upon one another: what I call a "fast" grid and a "slow" grid. The fast grid acts like an effective grid of 600'x600' (and 600'x1200' and 600'x1800' further south)...So in that sense, it isn't as dense as Portland's ...in terms of traffic flow is concerned.

Howard said...

Not sure of the reason for Manhattan's long east-west/short north-south, but one effect on the Upper East Side and Upper West side neighborhoods is that it allows for lots of people to live on the side streets (east-west) and lots of stores--especially corner stores--on avenues (north-south). This makes for great walkability and also has other positive effects, such as buses operating largely away from residences, except for larger cross-streets like 96th, 86th, etc.

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http://meadonmanhattan.wordpress.com/

Diane said...

Alleys might be difficult to see on Google Earth, especially if the picture was taken during the summer when tree cover can really obscure narrow ways. I wonder, though, how they effect the pedestrian experience of a city. I lived on one once and used the alley grid for walking as much as the streets.

Wendy said...

Intriguing. Who knew Denver and Bellingham had the same grid?

Chris said...

Daniel,
According to "The Geography of Nowhere" by James Kunstler, the original plan for Philadelphia was actually 10,000 acres, divided into a grid of 10,000 plots of an acre apiece - one for each of 10,000 family to subsistence farm on. Talk about uniformity! I can't imagine the planning nightmare that would have become with the invention of the automobile.

Great visualization! Very interesting stuff.

-Chris

Adrian said...

Howard's comment about New York's long narrow blocks allowing quiet residential areas away from noisy buses is interesting. Perhaps the ideal block configuration is small like Portland's, except every second north-south street should be a pedestrian/bike path only - no motor vehicles.

This would provide all the advantages of the small block (walkabaility, diversity etc.), with the advantages of the long narow block in creating quiet spots away from noisy motor traffic.