Tuesday, July 03, 2007

Non-Grid Transportation Networks

A number of people have asked me recently to write about cities (and regions) that have non-grid highway networks. Having just spent a week in an excellent example of such a city (sunny Pittsburgh!
), it seems like an excellent time to address the issue.

If you've ever been to Manhattan, you have probably discovered one of the truly amazing urban planning phenomena on this planet: there is no need for driving directions. If you know the address of a location, then you know how to get there. Nobody ever asks "What is the address?" and then follows it up with "How do I get there?".

The second question is never posed because New York (at least Manhattan north of Houston) is grid network that follows strict naming conventions. Avenues run north-south, and increase in numerical name from east to west. Streets run east-west and increase in numerical name from south to north. If I know that a restaurant is located at 5th Ave and 85st Street, and I'm at 3rd Ave and 45th Street, I need to go 2 blocks east and 40 blocks north. Voila!

There are a number of cities in this country (and in the world, for that matter), that have predictable and logical grid networks. Central Washington DC, much of Cleveland, downtown Philadelphia, and Chicago (in the Loop, anyway). I would venture to guess that tourists get lost far less often in these cities than in non-grid cities.

Cities that have non-grid transportation networks are usually built that way because of topographical difficulty. As I mentioned above, Pittsburgh is a great example. The center of Pittsburgh was originally Fort Pitt (a military fort), located at the tip of land where the Allegheny and the Monongahela meet to form the Ohio river. These three rivers have, over a few million years, carved remarkably deep (and steep!) river beds. It is impossible to build roads along straight, grid-based lines. Elevations change wildly as one passes between mountain peak and valley. It's a common sight to be driving along one highway and go underneath an overpass 150 feet above your head. The elevation varies a lot!

Ok, I'll stop here for the moment. More to come.


Blogger Bryen said...

Chicago, even outside of the Loop, has an excellent grid system. Don't let the diagonal streets (Elston, Clybourn, Lincoln, Archer, etc) fool you.

Even though all of the streets and avenues are named, not numbered (at least on the north side - south side streets do have numbers) the numbering convention used makes a lot of sense.. north/south from Madison and east/west from State, minor streets at 100 intervals, major streets at 400 intervals; 800 per mile (8 blocks north/south, 16 blocks east/west due to rectangular blocks vs squares.)

I moved here in 2003 and could find my way around within a couple of months. Directions are given by major intersections ("that's close to Peterson and California") which is generally all that's needed to know exactly where to go...

9:52 PM  
Blogger Silus Grok said...

Oh man! I can't believe you didn't mention Salt Lake City... and the Salt Lake City pattern is almost universally followed throughout Utah and other parts of the Mormon inter-mountain West.

It's a simple pattern:

The grid is rigid and (in Salt Lake County) county-wide, with streets running north-south and east-west. The square blocks are each 10 acres (appx 660 feet on a side — 8 blocks to a mile... though this varies outside of Salt Lake county).

The streets are named for their distance from the 0-point. In Salt Lake, the 0-point is the intersection of South Temple and Main. South Temple runs east-west and Main runs north-south. So we have streets 100 South, 200 South... and so on, down across city boundaries to the south end of the valley at 146000 South. Streets are named the same going east-west. There are streets that have conventional names, but always, parenthetically, have their grid designation (Hawthorne Ave is 550 South).

The kicker in all of this, though — and what really sets this all apart from the grids mentioned in the post (at least as far as I can tell) — are the addresses:

Say my address is 336 West 300 South. That means my home is located about a third of the way along the block between 300 West and 400 West... or, in the local parlance, I live on Third South between Third and Fourth West. And this works anywhere in the city... 240 South Main Street is half-way between 2nd and 3rd South on Main Street.

And this is so helpful... In NYC, if you've got the cross-streets, you know exactly where it is. But if you don't know the cross-streets, you're out of luck, because 550 X street and 550 Y street are seldom related to each other.

In Salt Lake, however, the address is the cross-street.

Of course, there are exceptions... most notable among them being The Avenues neighborhood.

Anyway, it's wonderful... and a breeze to navigate — though folks from back-East have to be reminded that SLC blocks are up to three-times as long as they're used to.


11:51 AM  

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