Having worked in communities big and small across the continent, we’ve had ample opportunity to test ideas and find approaches that work best. Urban design details. Outreach tactics. Implementation tricks. Many of these lessons are transferable, which is why we’ve created “Back of the Envelope,” a weekly feature where we jot ’em down for your consideration.

Today I offer a quick study relating cities of the US West to Leon Krier’s decidedly European Public Space Quantity Ratio.

First, consider Krier from Architecture: Choice or Fate?, page 147 (click for larger view):

His take on the subject:

A. 15 – 20% is too little Public Space

(Salt Lake City is an example of nearing too little)

B. 25 – 35% is the Good Proportion

(Portland is an example)

C. 50 – 60% is too much Semi-Public Space

(San Diego is an example)

D. 70 – 80% is too much Public Space

(Las Vegas would probably fit into this category)

And now mine (with the gracious research and graphic assistance of Graham Larson and Lori McLaren — click for larger view):

While I only comment on the quality experienced by Pedestrian and Motorist, I could include Transit riders as well, as all US West downtowns, with Seattle’s Streetcar nearing completion, now provide transit services.

My points of interest:

1. Salt Lake City fits into Krier’s “Good Proportion” percentage, and Andres Duany reveres the Plat of Zion. However, walking SLC can be very uncomfortable.

2. While San Diego is both relatively comfortable to drive and walk, due to short block length and average street widths, it is still too drivable due to mostly being one-way streets, and thereby not the most comfortable walking experience in the US West. That distinction belongs to Portland, which we would all agree is a very walkable city that nicely embodies Krier’s Good Proportion public space ratio spectrum.

3. The reason Krier’s percentages work, but not exactly in the US West, is because Krier assumes Public Space as consisting of Civic Space! The US West downtown percentages include very, very little CIVIC SPACE, consisting instead almost entirely of streets. I would dare say the amount of Civic Space in a typical square mile would total only 1% (this requires further study, of course, but I’m probably not far off).

4. As we enter the 21st century, these percentages should discern between lessening influential auto-oriented public space (parking lots and street travel lanes) and increasing pedestrian-oriented public spaces (civic spaces, street parkways, paseos, promenades, transit stations). Therefore, the Public Space categories for US West downtowns should be:

A. Built Private Realm: 55 – 60%

(taxable buildings)

B. Unbuilt Private Realm: 5 – 10%

(vacant/redevelopment land)

C. Auto-Oriented Public Realm: 25 – 30%

(streetscape, travel/turning lanes)

D. Human-Oriented Public Realm: 3 – 5%

(transit/civic spaces)

To conclude, I would recalibrate Krier’s Quantity of Public Space percentages:

A. 0 – 25% is too little Public Space

(You simply can’t put SLC in the pantheon of great downtowns just yet)

B. 26 – 39% is the Good Proportion

(Solid urbanism, Portland fits)

C. 40 – 60% is too much Semi-Public Space

(This is suburban character)

D. 61 – 80% is too much Public Space

(Too rural for coherent urbanism)

The greatest opportunity to build our downtowns into the 21st century will be found in re-purposing our streets and reconfiguring the street right-of-way. In San Diego, 40% of our entire land mass downtown is ONE-WAY STREETS! We also have a lot of vacant land, so I believe San Diego can greatly improve over the next 100-years, as can Salt Lake City. SLC’s streetscape and broad blocks offer tremendous development potential.

All of this leads to the question of Portland. Will it stagnate over the next 100-years? How will it continue to evolve? Only vertically? And, if vertical is their only option, how will they solve for their need of new civic space? Is a purposely built High-Line an option?

Thoughts and opinions are welcomed.

–Howard Blackson

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