Posts about Street Grids
Maryland and Virginia will both enact major new transportation funding bills this year. Neither bill says exactly which projects will be funded, but here are the top 10 projects in Maryland and Virginia that most deserve to get some of the funds.
1. 8-car Metro trains: Metrorail is near capacity, especially in Virginia. More Metro railcars and the infrastructure they need (like power systems and yard space) would mean more 8-car trains on the Orange, Blue, and Silver Lines.
2. Tysons grid of streets: Tysons Corner has more office space than downtown Baltimore and Richmond put together. Converting it to a functional urban place is a huge priority.
3. Purple Line: Bethesda, Silver Spring, Langley Park, College Park, New Carrollton. That's a serious string of transit-friendly pearls. The Purple Line will be one of America's best light rail lines on the day it opens.
4. Baltimore Red Line: Baltimore has a subway line and a light rail line, but they don't work together very well as a system. The Red Line will greatly improve the reach of Baltimore's rail system.
5. Silver Line Phase 2: The Silver Line extension from Reston to Dulles Airport and Loudoun County is one of the few projects that was earmarked in Virginia's bill, to the tune of $300 million.
6. Arlington streetcars: The Columbia Pike and Crystal City streetcars both have funding plans already, but could potentially be accelerated.
7. Route 7 transit. Leesburg Pike is the next Rosslyn-Ballston corridor waiting to happen. Virginia is just beginning to study either a light rail or BRT line along it.
8. Corridor Cities Transitway: Gaithersburg has been waiting decades for a quality transit line to build around. BRT will finally connect the many New Urbanist communities there, which are internally walkable but rely on cars for long-range connections.
9. MARC enhancements: MARC is a decent commuter rail, but it could be so much more. Some day it could be more like New York's Metro North or Philadelphia's SEPTA regional rail, with hourly trains all day long, even on weekends.
10. Alexandria BRT network: This will make nearly all of Alexandria accessible via high-quality transit.
Honorable mentions: Montgomery County BRT network, Potomac Yard Metro station, Virginia Beach light rail, Southern Maryland light rail, and VRE platform extensions.
Cross-posted at BeyondDC.
Daniel Nairn posted an interesting comparison of the street grids in various cities in the United States. This raised the question: why did various cities choose one block size over another?
Why, for instance, are the blocks in Tuscon, Arizona 400 feet on a side, while Portland, Oregon has 200-foot blocks?
The block sizes of most cities stem from the interaction of architecture and nature. Local climatic conditions affect the shape of a building and its lot.
In the north, the climate is primarily cold and dark, and in the south it's hot and sunny. This is more pronounced in Europe, where most of the precedents for American building types come from. These building traditions were brought to America through the different cultures that established colonies in the New World.
Thus, the cities laid out by the Spanish are significantly different from those laid out by the French, Dutch or English, not only in tradition, but also because of where each of these cultures settled in the New World.
In southern and Mediterranean climates, there is a lot of sun and heat. Having a building close to the ground is a plus, as the earth helps regulate temperature. Also, buildings usually don't exceed one or two floors to avoid heat rising up to higher floors. Traditional Spanish houses are long low affairs, with small courtyards giving a little light where necessary, but in general cool and dark.
In the northerly climates, it's important to let in light, so buildings tend to have tall windows, but they also need to deal with cold winters. Therefore, having a tall building is an advantage, as heat is retained through the stacking of floors. Keeping the lots small, narrow and nestled together helps retain heat.
These important factors explain why lots are the sizes they are. A city in the northern European tradition will have taller and narrower buildings. Lots would be relatively shallow, with a depth of only about 35' or so for the main block including requisite garden space. With these smaller lots, the block size could be relatively small as well.
Looking at Alexandria, Virginia as an example, we see a more "southerly" northern house, having a main block of 35 feet or so with a small wing attached and a small garden behind. The lots in Alexandria are slightly deeper because of this side wing but still relatively shallow compared to the massive blocks you find in old Spanish colonial cities.
San Buenaventura, (aka Ventura), California, where I lived for two years, has lots 400 feet by 400 feet, four times the size of Portland's blocks. Ventura was laid out according to the needs of a hot sunny climate. Like other buildings of the Spanish Colonial era, it has low, sprawling houses. This requires a lot more ground space, and so the lots need to be significantly deeper to allow room for a usable garden behind.
Pre-industrial cities needed gardens to grow produce and even raise small livestock. Almost all food had to be raised locally, so having a garden was essential to city living. After the Industrial Revolution, with the advent of fast travel, food could be brought to market from distant lands, so the importance of a garden began to wane. Thus we can see why Portland, founded in the latter part of the 19th century, could afford to have relatively tiny blocks.
The industrial city becomes less and less subject to the necessities of the environment, and so most American cities west of the Appalachians have block sizes of more or less arbitrary sizes. Anchorage could afford to have a big block size just as much as it could have a smaller one.
Today, with the advent of cars and air conditioning, the size and shape of a lot has more to do with the needs of the car and its parking than any other concern. Lot sizes revolve less around depth, and more around width, being in multiples of car widths for the garage.
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 a hundred 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. (Washington, DC has very little uniformity.)
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 the grid somewhat in a Planetizen post.
Crossposted on Discovering Urbanism.
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