low density walkability revisited

[mindstalk]

I still like my 2019 model of how even 3000 people/km2 can be kind of walkable (and bikable) if you do it right. Short recap: supermarket needs 8-12,000 people, so imagine a 2 km x 2 km superblock, with a market right in the center (along with bus/rail intersection). Furthest walk is 2 km or 24 minutes, from the corners, which isn't great, but many people have shorter walks, especially if density is non-uniform and clumps by the center. And 2km is 10 minutes on a slow bike, so *that's* nice. I also penciled in schools and stores and such.

At 12,000 people/km2 the scaling is easy: you have the same pattern, but in a 1x1 km superblock. Now the longest walk is 12 minutes, super easy, barely an inconvenience.

But what about 6,000? I found that annoying to think about and didn't talk about it last time. Annoyingly supermarkets might need just 8000 people... but that's 1/3 more than I have in 1 km2.

But I realized, if you take the 12,000/km2 model, and then simply remove every other supermarket in a checkerboard pattern, then you have the right population ratio to support the markets, but still no one has to walk more than 12 minutes, 1 km. You've increased the *average* walk time -- a bunch of people who were in 0-3 minutes are now in 9-12 minutes -- but not the max.

Probably not coincidentally, I read somewhere that car use drops off around 10-20 units per acre; if that's gross acre, then that's 2500-5000 units per km2, or 6250-12,500 people/km2 if each unit averages a 2.5 person household.

(And if you're wondering how that compares to real cities, this older post is useful, though sometimes neighbhorhood density would be more useful. But given that cities tend to be largely residential, a US city of 1000-2000 people/km2 is obviously not going to have much walkability.)

Comments

[mtbc]

It seems that you're indeed accumulating detail in a workable and appealing model.

You're thinking some big hiking backpack, and/or bicycle with panniers, or somesuch, for supermarkets? Though I'm still particularly annoyed with Trader Joe's insisting on paper bags which, even doubled, get barely 100m in the rain before disintegrating. Maybe post-COVID we get to reuse decent grocery bags again.

[squirrelitude]

That might just be a Trader Joe's thing. The grocery stores I've used recently (a supermarket, and a small corner grocery) have both been fine with reusable bags.

I often walk to the nearest grocery and either carry the bags (small load) or use a collapsible cart (large load), or if I'm in a hurry I use bike panniers (small) or a bike trailer (large).

[mtbc]

I haven't been able to test since returning to the US as the pandemic seemed to make everybody disallow reusable bags but I should look out for that being relaxed.

[mindstalk]

Probably too late for anyone but you to notice this, but copying from Slack for posterity:

Walkable shopping usually involves just carrying bags home, maybe a backpack too. Even shopping for 3, I'm not sure my father was any different, though I got sent out too, and when older my father got a personal shopping cart.

urban shopping is generally more frequent than once a week, and often done on the way home from work not a separate trip. and if it is separate, hey, 5-10 minute walk.

My shopping has mostly been "I'm out of something, let me get it"

I've lived almost my entire life in a 15.minute walk of a supermarket. I whine if it's more than 10 minutes.

[mtbc]

Done frequently, and with a backpack, I can sure imagine it, though I've not usually lived anywhere near as close to anything I'd call a supermarket. Here in the city my nearest is still nearly an hour's walk away but I guess that's what low-density neighborhoods get one. From Belmont I'd typically go to the Aldi six miles away though the nearer Trader Joe's (Alewife) would have covered some bases and I expect there was other stuff closer too.

[mindstalk]

And then I walked through SF Chinatown today, where there was a produce market across the street from a produce market, one block down from a produce market...

(I suspect there's enough density and business to support a full blown supermarket but the old buildings don't have room for one.)

(Also SF's Chinatown is as dense as Manhattan, or was a few years ago.)