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November 6th, 2019

a low density urban model

So, a little model I came up with. kchoze said the US has one supermarket per 8500 people; let's say a good supermarket needs 12,000 people. Let's say this city has 3,000 people/km2 -- less dense than LA, not much denser than the threshold at which Americans in one survey said their neighborhoods were 'urban'. ('suburban' started around 400.)

So 12,000 people is 4 km2, or a 2x2 km square if uniformly distributed. Assuming the markets are themselves uniform, in a grid-like street pattern, no one has to walk more than 20 minutes to the market -- 1 km down, one 1 km over, say. Now, that's longer than I would like to walk, especially if having to make many trips for a family, so maybe 25% of the people (beyond 15 minutes) drive, or 50% (beyond 10 minutes). That's still a lot who don't have to.

Or maybe they bike -- even a slow ride wouldn't take more than 7 minutes. Is it safe? It could be -- place arterials every km, the whole ride can be on slow residential streets. Or maybe there's a protected bike path along the arterial.

Maybe the density isn't uniform -- it could clump up around the market, thin out near the edges of the square. This would happen naturally if there were a train or light rail station and commercial cluster around the market (assuming zoning *allowed* it to happen.) So a diversity of housing preferences would be catered to, plus fewer people would be living far away from the market.

The US also has 1 convenience store per 2000 people; let's say per 4000 people, so there are three such stores somewhere in this square. Probably a few other thing as well.

12,000 people would have around 1800 kids of school age, so depending on school size you could have one big school every few squares, accessible by walk+train, or multiple small schools easily walkable within a square. Likely small elementary schools, and a bigger high school for lab/gym/language stuff. But it could go either way.

It's no Osaka or Florence, but it seems a moderately walkable neighborhood, and with decent light rail or bus service to elsewhere you could likely get by without a car. All at a density that's a fair bit below what I usually consider necessary.

What's missing from real US places? Well, zoning that allows supermarkets and other businesses every couple kilometers, for one thing; if your city zones for 5 miles of pure housing, that kills this dead. Gridlike[1] streets -- if your suburb is built around dead ends off of arterials, travel distance can go up a lot. A high frequency bus line or such every couple kilometers.[2] Keeping neighborhood schools and not replacing them with mega-schools on the edge of town.

[1] Japanese cities are often terrible at having simple straight lines, but the connectivity of small residential streets is similar to what you'd get from a clean grid.

[2] Can you support that at this level of density? I don't know -- but if you provide the service, and don't go out of your way to favor cars, maybe. Just looking at one 2x2 km square, if 6,000 of the residents would otherwise spend 30 minutes a day driving, that's 3,000 person-hours a day. Seems like you should easily be able to afford a few bus drivers circulating around -- say 12 at once (one line every km, one active driver per 2 km, each way) for 8 hours, double for an evening shift, that's 200 person-hours a day.

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Hobart Nov 6

Now in Hobart.

JetStar bag drop in Sydney was way less efficient than Qantas in Brisbane. 17 minutes after I had printed my bag tags, just to be able to hand the bag over. A friend snarks that the purpose of JetStar is to make you wish you had paid Qantas. Wait, that might actually be literal:

"It is a wholly owned subsidiary of Qantas, created in response to the threat posed by low-cost airline Virgin Blue. Jetstar is part of Qantas' two brand strategy[6] of having Qantas Airways for the premium full-service market and Jetstar for the low-cost market."

Once again, no one asked for any ID -- not at bag check, not at security, not at boarding.

Flight was okay. Announcements were loud. I was glad I paid AUD$18 for exit row legroom. Nothing is free, even a small bottle of water would be $4.

Hobart airport low but sprawling, and far from the city. More to the point, no public transit to the airport; ended up taking a SkyBus shuttle. Got yet another transit card, and headed to my place.

And yet another Australian bus system doesn't announce stops. They did have numbers on bus stop signs, but I missed #6 and got my #7 only because of GPS. The stop there didn't even have the number. So much for that coping mechanism.

Tasmania gets rain! It's grey and green! With pine trees, not palm trees! So different.

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Damien Sullivan

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December 2020



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    I use Yardley's English Lavender soap, and a bar lasts a good long while.
  • 19 Sep 2018, 20:20
    The block south of me is the 400s, whereas mine has addresses like 17-11.

    Ah, gobbled up in the rift, no doubt.
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    No, but my roommates had a cat that would stalk and attack me.
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