The Speed Burden [Costs of Sprawl Series]

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aerial image of Florence, Italy beside Atlanta interstate interchange, both at the same scale

Left: Renaissance Florence, Italy - Right: Atlanta interchange (both at same scale)

   The need for speed devours huge chunks of American cities and leaves the edges of the expressways worthless. Busy streets, for almost all of human history, created the greatest real estate value because they delivered customers and clients to the businesses operating there. This in turn cultivated the highest tax revenues in town, both from higher property taxes and from elevated sales taxes. But you can't set up shop on the side of an expressway. How can cities afford to spend so much to create thoroughfares with no adjoining property value?

   Let's first look at the four basic problems with speed:


   Increasing speed a little bit requires a big increase in the size of curves. At 20 miles per hour, any car can handle a curve with a 15 foot radius, so you'd think that tripling the speed would triple the radius, right? Wrong. At 60 miles per hour, curve radii are usually a few hundred feet, not the 45 feet you might guess.

Lane Width

   Faster roads need wider lanes. An 8 foot lane can handle 20 mile per hour traffic, but at highway speeds, you need 12 foot lanes.

Medians & Shoulders

   High-speed roads need wide medians and shoulders because a car can roll hundreds of feet beyond the point of collision or loss of control when it is traveling at highway speeds.

Number of Lanes

   It makes no sense to use all that land on either side for a two-lane highway, so high-speed thoroughfares usually have at least four lanes, often several more.

Florence vs. Atlanta Interchange

Florence, Italy satellite image

Florence, Italy

   Look at Florence above… the blocks are tiny, and the streets are never much more than hairlines. From this high up in the sky, the intersections look like sharp right angles. This is because Florence was laid out for people and horses, which can turn on a dime. Cars drive on these streets today, but they drive slowly, which is far safer for the pedestrians.

   The Atlanta interstates are each as wide as 2-3 blocks of Florence. The entire Duomo (the cathedral in the center of Florence that arguably began the Renaissance) could fit in one of the inner loops of the interchange, as you can clearly see. The central core of Florence, from the Duomo to the river, would fit inside the inner box of the interchange. The world was irreversibly changed by the people living and working in Florence who gave birth to the Renaissance. The interchange will never change the world… at best, it gets a small fraction of Atlanta workers to their jobs a bit sooner, barring any accidents.

Atlanta interstate interchange satellite image

Atlanta interchange

Seaside vs. Miami - A Closer Look

   Let's analyze this at a larger scale. Each of the following two images is a half-mile wide and contains 90 acres of land or sea. The first is DPZ's Seaside, Florida, which as you may know is the birthplace of the New Urbanism. Its fabric is not so different from the scale of neighborhoods we built everywhere in the US before World War II. The second image is an urban interchange along Interstate 95 just north of downtown Miami. I selected this location because the urbanism is relatively tight here, and the curves are minimal. I could have picked something further out in suburbia that was looser, but that would be like shooting fish in a barrel.

Seaside, Florida satellite image

Seaside, Florida (same scale as I-95 in Miami)

Looking at these images, it's immediately clear that there's a lot more paving in the Miami image than in Seaside. But if you start counting blocks, you'll see that there are 27 blocks of urbanism in Seaside (even though 13 acres in the lower left corner is lost to beach and sea) while there are only 15 blocks in the Miami image, depending on what you consider a block. That gives us a pretty good hint that maybe there's more real estate value above than below.

I-95 and surrounding neighbhorhoods in Miami satellite image

I-95 in Miami, Florida (same scale as Seaside)

The Speed Burden - Land Area

Seaside, Florida plan showing areas of real estate value and thoroughfares

green land: has real estate value ~ red land: no real estate value

   One measure of land value is acreage. In Seaside, 80.5% of the available land has real estate value; only 19.5% of the land is taken up in thoroughfares. Note that I have included parks, greens, squares, and plazas as having real estate value even though they cannot be sold because studies have clearly shown that open these types of natural spaces create more real estate value in nearby lots than if they had been sold as private lots.

   Only 62.6% of the land in the Miami example has any real estate value because the thoroughfares consume 37.4% of the land. Based on Seaside, it would be reasonable to say that about 20% of the land in a traditional neighborhood should be allocated to thoroughfares. The Miami example consumes almost twice as much: 37.4%/20%-1 = an 87% Acreage Speed Burden. How can we afford to burden the land with 87% more thoroughfare acreage than necessary for a vibrant walkable environment?

Miami plan showing areas of real estate value and thoroughfares

green land: has real estate value ~ red land: no real estate value

The Speed Burden - Frontages

Seaside plan showing full-value street frontages

green frontages: full value

   Acreage isn't the only metric of land value. The "front foot," or length of the front property line is another metric of real estate value that is perhaps more useful than acreage. In Seaside, every single foot of frontage is full value, meaning that it either has addresses of private lots along it, or it opens into parks, greens, squares, and plazas. Even though only 77 of the 90 acres are buildable (the rest being beach and sea) Seaside has generated 36,200 feet of full-value frontage.

   The Miami example doesn't fare nearly so well. The frontages along the I-95 and its exit ramps have no value at all. Even if you wanted to open up a shop there, it's illegal to do so. There are 9,531 feet (almost two miles) of worthless frontages here. Some of the frontages are shown as "partial value." These are frontages that are either 100% side streets (no front doors) or frontages that have been ruined with big parking lots just behind the sidewalk. There are 6,303 feet of partial-value frontages in this image. That leaves 17,820 feet of full-value frontage, for a total of 33,654 feet of frontage of all types. Interestingly, Seaside generated a half-mile more frontage on 13 less buildable acres, and all of it is full-value, whereas only 52.9% of the Miami frontage is full-value. So even if Seaside had built as much on the full 90 acres instead of the 77 buildable acres, that would still be a 47.1% Speed Burden based on full-value frontages.

Miami plan showing full-value, partial-value, and worthless street frontages

green frontages: full value ~ olive frontages: partial value ~ red frontages: worthless

   How can we afford to pay so much and get so little? Cities really do need to rethink their infrastructure priorities. We are beyond the point where we can spend enormous sums of money with little or no return. Municipalities, from cities to towns, villages, and hamlets, all need to take a careful look in the mirror each time they want to spend money and ask themselves: "What is the return on this investment?"

   ~Steve Mouzon

   Note: This post is part of an extended BlogOff on Return on Investment (RoI) of municipal spending. Hazel Borys started the BlogOff with the following post… please join us!

   1/27/12 - On the Street: The DNA of place and the ROI of movement, Hazel Borys

   Another Note: This is part of an occasional series on the costs of sprawl I started in March 2011 with Costs of Sprawl - Part 1. Lots more to come… hopefully more quickly next time.

Legacy Comments

Steve Mouzon · Board Member at Sky Institute for the Future

Renaissance Florence no larger than a mega-interchange? No kidding... have a look. The need for speed has costs we don't even consider... but should.

Feb 20, 2012 12:49pm

John Paul Weesner · Senior Landscape Architect / Urban Designer at Kittelson & Associates, Inc.

What a great comparison. How can we have a Renaissance (especially in the small crawl space under the curved exit ramp?)

Feb 20, 2012 12:56pm

Sky Institute for the Future

Thoughtful presentation Steve. Well done!

Feb 20, 2012 1:19pm

Gil Lyons · Co-Founder, Director at Sky Institute for the Future

Great post Steve. Logical, well documented, and images clearly support your assertions. Well done... as always!

Feb 20, 2012 1:22pm

Patrick Kennedy · Owner at Space Between Design Studio

Steve, this is excellent and far more concise than every attempt I've made at saying the same thing.

Feb 20, 2012 1:24pm

Patrick Kennedy · Owner at Space Between Design Studio

I should add that the worthless frontage is a critical one to examine, one that I've been pointing out to people that will listen in Dallas. We've badly OVERvalued the highway frontages. And the evidence is the gradual but inevitable decline witnessed of highway properties. They start as new shiny hotels or office buildings, but invariably disinvestment, decay, and destruction leads to gas stations and xxx shops (highest and best use of highway frontage?).
I suspect there are a few reasons for this. Primarily, the initial misinvestment is due to the accurate notion of developers that traffic equals value. The more people moving past your property, the greater value there is on the site. This is true with the internet, it is true with logical/rational cities (ie not the illogical, irrational cities of the sun belt). Because the format of this traffic is inherently inhumane and sociofugal (yet we remain very human and in possession of human needs for social contact and exchange), a tension is built into the illogical cities: to get away from the Bad traffic generators, but be near them at the same time. Hence, we get retailers establishing defensive postures with parking out front, malls that are walkable internally but only internally disconnected from context, and faux town centers aka malls without roofs aka malls in drag.
Contrast these with the High Streets or legitimate Main Streets of the logical, rational city, where a direct relationship persists between traffic (just not all car traffic, but all forms of people- and place-friendly movement) and value. The underlying dynamic is what Bill Hillier's work points to, spatial integration, aka what we might call total or global accessibility. When you start running the analytics (such as space syntax or intersection densities) on the highway frontage format, you see that the actual measurable accessibility is far lower than the real estate market thinks. There is a disconnect.
The smaller block size and greater density (which I argue is a by product of demand via accessibility and integration) makes for increased accessibility for more people. They may be moving more slowly, but can meet their need for social and economic exchange for more efficiently (cost, energy, time, and infrastructure) than the format based on speed. It is engrained in all transportation policy that speed is king, as you rightly point out, and it is destroying our cities and their resilience. 
The difference between the two (logical vs illogical) is that the value of the rational city is predictive and persistent. Place and location matter. But in the illogical city, "if you build it they will come" mentality is pervasive and built-in. Location matters not and everything is in a constant state of conflict and cannibalization.

Feb 20, 2012 1:41pm

Mike Huston · Works at DPZ Partners

Great visuals to educate the non-believers, well done.

Feb 20, 2012 3:54pm

John Olson · Director of Urban Design & Landscape at Altitude Land Consultants, Inc

Brilliant as always Steve! It still amazes me when I see streets, new streets albeit, with drive lanes of 15-ft to 16-ft. Even more surprising is that these same streets are posted as 35 mph speed limit.

Feb 20, 2012 9:02pm

Steve Mouzon · Board Member at Sky Institute for the Future

I mentioned Hazel Borys, but can't believe I didn't mention Chuck Marohn in this post! Both Chuck, of StrongTowns, and Hazel with her partner Nathan Norris of PlaceMakers have been doing lots of work on ROI for municipal expenditures. If you don't know these guys, you should!

Feb 21, 2012 6:41am

Hazel Borys · Managing Principal at PlaceMakers

Sobering numbers, Steve. But with a lot of promise about what our savings might build for us. Since we simply can't afford "fast" anymore. --Looking at this, I'm thinking that the US EPA estimate of 32-47% less expense to build in compact patterns instead of in auto-centric patterns might be a conservative estimate.

Feb 21, 2012 11:10am

Steve Mouzon · Board Member at Sky Institute for the Future

Want a horror story for weekend reading? Have a look at the next installment of the Costs of Sprawl: Cheapways. A trillion-dollar mistake:

Feb 24, 2012 4:54pm

Joseph Readdy · Washington State University

Speed kills urbanism, My panel at CNU XIX. Perhaps a less extreme example comparing two Portland streets with the same right-of-way, nearly identical average daily traffic trips (27,000 versus 27,500), posted speeds nearly the same (30mph versus 35mph). The big differences were actual speeds (22mph versus 37mph), density (14.5 residents per gross acre versus 9.3), number of traffic accidents (14 versus 48 over 12 months), land value ($75.50 s.f. versus $39.00 s.f.), and assessed building value ($186.50 s.f. versus $38.00 s.f.). 
I didn't show photos of the context, but you can imagine what each of these places look and feel like and where you would rather live, work, and play.

Feb 24, 2012 5:46pm

Kyle Zheng · Youtubers at Freelance

Wow, great examples of Urbanism vs sprawl. For those that think highways = freedom, this proves the opposite.

Feb 26, 2012 1:09am

Michael Hart · University of Cincinnati

Great stuff. Hey since your in Miami how about something on the value of the parking spaces in front of the News Cafe? You know the high dollar see my car parking spots.

Feb 28, 2012 8:48am

William L. Fisher · University of Illinois at Urbana-Champaign

common sense. drive less. walk more. waste less. save money. be healthier.

May 7, 2012 3:23pm

Jon Saskboy Klein · Regina, Saskatchewan

I'm trying to locate the exact Atlanta interchange, could someone help me located it on Google Maps (and provide link or co-ordinates please)?

Jun 12, 2014 5:32pm

Brian Bober · Atlanta, Georgia

This is misleading. One is downtown Florence, whereas the other is an interchange just outside the city limits of Atlanta, in the Smyrna/Vinings/Cumberland area (with a little of Sandy Springs and Buckhead) at the I-75/I-285 interchange. It helps to zoom out a bit for a more realistic comparison. See better examples here 
Florence has completely empty spots mixed in with dense areas, whereas the Atlanta suburban area is more consistent.
Of course, it should be no surprise that the 3rd most densely populated area in metro Atlanta, actually slightly outside the city limits, doesn't compare to Florence, Italy which was built back when cars didn't exist.
I think the real comparisons I've provided here shows that small nodes like the one in this picture can be developed into walkable communities with infill. That is already in the work for this area, and has been for quite a while.
This is where the new Braves stadium is going in, so it's been an area everyone is picking on lately. Back in the early 2000s, way before the Braves announcement, there was a vision for this area, known as the Cumberland CID and a self-taxing district. It included bridging the highway with walkable promenades, known as Blueprint II, though I think it should go further, and probably will when the Master plan process is picked back up, after it was disrupted by the Braves' announcement.

Jun 16, 2014 9:52pm


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