Thursday, April 12, 2012

The Value & Efficiency of Small Block Structure

Tom Vanderbilt has a great series on the pedestrian over at Slate (part 1, part 2, and part 3). Vanderbilt has been doing great work since I first discovered him with his book Traffic (and presumably earlier as he's a great writer and diligent researcher). As time permits, I'll unpack other parts from this series, but for now I want to focus on a few nuggets from part 2, which digs into some of the computational and empirically observed physics of pedestrianism, walking. ht to Mike Dunlop for alerting me to this series.

Within this piece, Vanderbilt speaks with several experts on pedestrians, one of which has created a logarithmic modeling program not dissimilar to vehicular traffic modeling. The person he speaks to at the company who developed "Legion," the modeling program, drops two incredibly poignant and significant nuggets. The first:
At the heart of the company’s algorithms is the idea that a “person, when they walk, is seeking to minimize their dissatisfaction.”
When I read this I nearly jumped out of my chair. Before I could express myself (to myself), Vanderbilt beat me to the punchline, "like life itself." Yes. This is an inescapable truth. To understand cities, understand people. To understand complex systems look for the simplest rules operating the system. In the case of people, it is emotion. Minimizing dissatisfaction.

Vanderbilt and the dude from Legion discuss several aspects of the model including the increased efficiency of congestion. Well, isn't that interesting. Furthermore, they talk about the limitations of the model (as all statistics are merely abstractions of the real thing). And that is that people have to be going somewhere, and in a hurry at that.

In many ways, it's sort of poisoned by the same thinking of the vehicular transportation models. All "people," as demonstrated by dots on the screen, are commuting. Moving. None are staying. And what is one of the first qualities of a great place? People linger. They want to stick around. As Jan Gehl often says, "great places are like great parties."

As Vanderbilt writes:
Modeling pedestrians works best for discrete flows in concentrated spaces, when masses of people are trying to get somewhere with purpose. “We can’t do people loitering in Times Square,” says Plottner. “We don’t understand why their behavior is what it is.”
And therein lies the rub. Once again, the model is entirely quantitative, reductionist, and overly simplistic. It's all about moving people. Efficiency. But the question remains, are there ways to measure both qualitatively and quantitatively? We return to the first quote as Vanderbilt continues:
But this simple statement—minimizing dissatisfaction—explains a lot. It is why people take the escalator (and disdain elevated walkways or subterranean tunnels), it is why pedestrians will begin to rampantly jaywalk if you make them wait too long, it is why they trample “desire lines” on aloofly chained-off college quadrangles. As a British engineer once told me, “pedestrians are natural Pythagoreans”—they will always seek the shortest path.
I've written quite a bit lately on desire lines and the invisible city. More importantly, the disconnect between the constructed and often "planned" physical city with that invisible city of desire lines and real efficiency of movement AND building space.

The answer is in the network and more specifically a balance of space for movement and space for staying. Smaller street/block structure has repercussions in both movement efficiency and efficiency of land use and real estate value. In terms of movement, a small block structure and compact, highly interconnected grid network means a variety of route choice. It instills an implicit intelligence in the user. You can adapt by day, time, necessity, and congestion.

As for real estate, a question:

Q: What is the most valuable real estate space by square footage within a retail, residential, or office space?

A: The windows. Or in the case of the ground floor, the storefront.

Now I return to a graphic I often use:


If you've never seen this before, it is ancient Rome (planned) and modern Rome (unplanned but self-organized). What it represents is a city that evolved from a singular "masterplanned" vision to one that is more useful to the millions of inhabitants and visitors to the city. The desire lines are beaten into the city creating more direct routes, more choice of movement, and perhaps more importantly more valuable linear store frontage.



As you can see there is significantly more valuable "interface space," where buildings interact with the street, because of the smaller block size. In the modern Rome, there is increased total square footage of built space, smaller blocks, more choice of route, more human-scaled open spaces (ie no overly grand spaces), and far more linear square footage of building space. There wasn't much of a grand plan, per se (though quite a bit of Rome has been shaped by a central authority, think Sixtus, Mussolini, etc.), but not this part. This was merely 2,000 years of millions of people making millions of decisions every day. And they made these decisions based on??? That's right, emotion, aka minimizing frustration aka maximizing satisfaction.

And guess what? I measured all of the linear building frontages of each of these to scale to see the relationship.

Total Building Frontage (linear):

Ancient Big Blocks: 11859
Modern Small Blocks: 27977
Verdict: Modern small blocks has 2.36x more linear frontage.

Then I found total floor area if these buildings were all single floor (because of the whole "efficiency of scale concept"), which has more square footage:

Ancient Big Blocks: 355770
Modern Small Blocks: 419655
Verdict: Despite the smaller buildings, modern small blocks have 1.18x more square footage.

But what about value of that square footage? Let's say the first 10' of building depth, "the room with the view," has a 2x premium over all other floor space. Factoring in premium to floor space near building interface (FYI: I'm hypothetically using $30/ft premium space and $15/ft standard space):

Ancient Big Blocks: $7,115,400
Modern Small Blocks: $10,491,375
Verdict: Thats's 147% more value to the small blocks with more storefront space.

But we also stated that this premium can be extruded upward into value for residential or office space above. So let's say all of these buildings are 4-stories:

Ancient Big Blocks: $28,461,600
Modern Small Blocks: $41,965,500
Verdict: That's 13.5 million more for the small block style of development

Which occupies the same total area if you recall since it is the same site. So what does this equate to in terms of value per gross square footage (both built space and open space):

Ancient Big Blocks: $46.53 / sq.ft.
Modern Small Blocks: $31.5 / sq.ft
Verdict: In other words, about a 50% premium for the small street and block structure.

(Caveat: the only numbers that are truly measured are the building perimeters. The rest are used for rhetorical purposes only. But you already knew that since that is what all statistics are used for under the guise of objectivity and accuracy. For more evidence in this regard, see the quotes above from the engineers themselves.)

In a modern American context, it means disciplining development, which too often thinks it needs an efficiency of scale. And it's for the development's own good. We have 6x more retail square footage per capita than the European country with the greatest amount (Germany). We have huge stores, much of which is for storage, which could be kept anywhere else than the valuable square footage it currently occupies. In other words, it is far more valuable and efficient use of land to have more storefront/window space regardless of use in high traffic areas than increased square footage deep in the bowels of a building (unless it is storage, industrial -- and there are better places outside of the city for that).

Ideas like "efficiencies of scale" make us think of Walmart, where we can get everything we need in one place. Except we have to sit in traffic, before trudging through a parking lot, past the miserable greeter, then down each of the soulless aisles to those "wants and needs." Sadly for that concept of efficiency of scale, it has a limited shelf life. The space is valueless and will someday be replaced.

On the other hand, in this part of Rome you can also get everything you need. I know, because I didn't live far from here. And the real estate space is far more valuable.

Perhaps it is time to start questioning what efficiency really means? The efficiency of one particular place in a vaccuum? Or the larger overall system of both movement and place. Of compromise and purpose. Point being: the city is far more complex than any formula could ever hope to distill. Why? Human emotion is complicated.