I am lucky enough to live in walking distance of a grocery store (at least, when I can actually afford to shop there). It’s five or six blocks away and I have no problem carrying a half a week’s worth of groceries home. Even in the urban core of a city like Philadelphia, this is a nice trick: the supermarket I go to is also the closest supermarket to the corner of Broad and Fairmount, a corner that’s a lot closer to Center City than where I am — only there, it’s a mile or so away instead.

Making it possible for everyone to walk to a grocery store essentially requires that they are spaced, on average, a mile apart from one another. This means that the closest grocery store is no more than half a mile from any given residence (i.e. every grocery store has a 1 square mile service area).

The problem with this should be self-evident. Grocery stores are low-margin businesses, which means that they need a lot of purchases in their respective service areas to survive. This in turn means that, as their service areas constrict, the population densities of those service areas must rise. If, as this post suggests, a population of 15,000 to 20,000 is necessary to sustain a 35k-50k sf full-service grocer, and these grocers are placed 1 square mile from each other, then they would need to have populations of 15,000 to 20,000 ppsm to be self-sustaining at that locational density.

Keep in mind here that South Philadelphia has a population density of 16,771 ppsm, itself some four times the median American urban population density of ~4,000 ppsm. For grocery stores to be close enough for everyone to walk to, then, living arrangements would have to be more akin to what we see in the big Northeastern cities than they are in Cincinnati or Seattle or Salt Lake or Denver. And of course you have to ensure that convenient walking paths to the grocery store exist within your service area.

To make a long story short, then, while Abbotsford’s residents desired the ability to walk to their grocery stores, unless they’re willing to make significant spatial tradeoffs, it will never happen. If 15k people are needed to sustain a grocer, and they have just over 130,000, then the city can support 8.67 grocers (let’s call it 9). That’s 9 over 145 square miles, or one grocer per 16 square miles.

If the service area is 16 square miles, then the radius of the service area is 4 square miles — some eight times that of our “walkable” grocers! (We can see this by realizing that the total trip distance for our outlying resident is effectively the service area’s diameter.)

This is an excellent example of how population densities matter. With a population density of 921 ppsm, Abbotsfordians are asking for something that neither the city nor interested grocers really can deliver on — they’d have to get a lot denser first, about as dense as Vancouver proper (13.6k ppsm). Even though Vancouver has Canada’s least affordable real-estate market, this is unlikely.

Indeed, the population density sheds some light into why Abbotsford is Canada’s most car-dependent city. It’s built to be that way. Its population density doesn’t even clear the threshold for running bus routes (1,000 ppsm). While it might be clear Abbotsfordians want a walkable city (and, I might add, more walkable, connected cities in the Fraser’s alluvial plain would help alleviate Vancouver’s housing crunch), the question is: are they willing to make the necessary choices to become a walkable city? Are they willing to redevelop their center and make it a proper urban place?

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