Category Archives: Urban Systems

Evolution vs. Plans


Assuming we started with an undeveloped wilderness,  cities emerge at selected points (typically points with natural accessibility advantages over their neighbors, such as ports and harbors, or water falls, or railroad junctions). But they evolve from wilderness to city over time.

They do not generally evolve because someone built city-scale transportation out in the country and waited for the people to arrive.

Instead it is a ratchet: a few people, some transportation network investment; some more people, more investment; even more people, still more investment, and so on, until something resembling a city emerged.

While the infrastructure may slightly lead the development (as in the Streetcar Suburbs or London’s Underground) those developments in general contiguously extended the urban environment in appropriate steps, and were accompanied by development in the near term (failure to see development would have led to bankruptcy for the line).


Plans aim to take this chaotic, unpredictable, evolutionary process and put a sheen of order upon it.

The general problem with public sector transportation and land use plans is that they are static. They are made for one point in time. They are  snapshots in a world with 24 frames per second (for eternity), and for which we don’t know the ending (“no spoilers”).

Life-cycle of rail in the US. From The Transportation Experience, Figure 6-4
Life-cycle of rail in the US. From The Transportation Experience, Figure 6-4


They design for maturity and implicitly assume that the mature (built out) city sustains. The evidence from the life-cycle for every mode (or technology) is that its scope and extent are continuously changing.

The mirror of this problem is  they ignore the path that gets you there and all interim states, as well as changes in behavior and technology that may occur in the interim.

The third problem with plans is that they address future problems that don’t exist today, when there are plenty of problems today that remain unsolved. Trying to better manage how will people get around or from or to a site which might (or might not) transform from country to city, or even low density suburb to high density suburb, in 30 years when there are plenty of ways to help people get around better today is an exercise in pointlessness, whose primary objective is to transfer resources from the public to selected (and one presumes politically influential) landholders.

There is nothing wrong with having a vision. It presents a direction in which to proceed. The most important thing is the next step (or two) though. Each step you take in one direction is a step farther away from destinations in other directions. But the path on which we are walking is shrouded in smog. Our vision is simply our imagination (or consensual hallucination) of what lies down the road. We have never been there before. But we must recognize, we never will reach where we think we are going.

City vs. Country

One of the many dysfunctions in transportation and land use planning is our collective inability to recognize the difference between city and country.

It’s really not that hard. In the country  distances between buildings are large, while in the city they are short. In land use jargon, densities are lower in the country than the city.

City Mouse and Country Mouse
City Mouse and Country Mouse

The most useful form of transportation varies between city and country.

In the country, individual, point-to-point, on-demand service (foot, horse, bike, car) saves a great deal of time over feasible shared, scheduled, fixed-route services (transit). That time savings offsets the individual cost savings from sharing a vehicle with other passengers.

In the city, shared transit services are on the whole less expensive to the user and society than individual services. The small increase in time is offset by cost savings from sharing. The greater density allows more frequent service and more direct service nearer the traveler’s trip end points.


In idealized low-density places like Wright’s Broadacre “City”, local transportation was clearly individuated, to the point it appears everyone has a private gyrocopter.

Howard's Garden City (1902)
Howard’s Garden City (1902)

In Howard’s Garden “City”, individual transportation was used to get around town, and to the inter-municipal railway.

In Jacobs’s New York City and Toronto, walking was used to access transit for longer distance urban and inter-urban travel, while the car was not especially welcome.

From both a transportation and land use perspective, each of these works on its own terms (assuming gyrocopters actually work).

Greenwich Village, New York (wikipedia)
Greenwich Village, New York (wikipedia)
Wright's Broadacre City (1934)
Wright’s Broadacre City (1932)

Stable points

Green Routemaster Bus serving suburban and exurban London
Green Routemaster “Country Bus” the kind that used to serve suburban and exurban London


Routemaster Bus (from wikipedia)
Red Routemaster “City Bus” (from wikipedia)

In short, in the current technological environment, there are two stable points: one where a sufficient number of people have abandoned their personal cars and use transit daily that transit is sustainable with high frequency and ubiquity; and one where people keep their cars and use transit on special occasions (to go downtown or the State Fair for entertainment, e.g.).

Once the car is owned, the marginal cost of the additional trip to most destinations (since free parking is found for something like 99% of all destinations in the US, gas prices and taxes are low, and we don’t have road pricing) is sufficiently low it outweighs the combination of low costs of shared transit vehicles with higher travel times.

A metropolitan area is large enough to contain multitudes. There can be a center where people can live car-less because the transit (or walking or biking) is good enough for daily city-based work and non-work trips, and a countrified-edge where people can live transit-less, since living and working in the suburbs is seldom a market transit can well serve (except as an accidental spillover where people are lucky or skilled enough to have home and work aligned on the same radial transit line).


Traffic Jams Make Cities Splinter into Subcenters: A rule of urban expansion could guide smarter growth – SciAm

I get quoted by Sarah Fecht in Scientific American (310(2)):

Most of the world’s cities started from an important marketplace or town square. Over time, they developed multiple centers where people could work, shop and play. But why? Some economists have suggested that cities fragment because of agglomeration—businesses that spring up in clusters increase their chances of success.

Yet physicists have arrived at a slightly different explanation: traffic jams. Marc Barthelemy and Rémi Louf, both at the Institute of Theoretical Physics in France, designed a mathematical model to explain how cities and their surrounding suburbs evolve. Their research suggests that as a city grows and congested roadways make it increasingly difficult to get to the center, subcenters emerge along the outskirts. “It’s an interplay between how attractive the place is and how much time it takes to go there,” Barthelemy says. Cities with accommodating transportation networks remain centralized longer, he adds.

The physicists validated their ideas using data from 9,000 U.S. cities and towns of different sizes.

A better understanding of how metropolitan areas evolve could prove useful, considering that two thirds of the world’s population is expected to live in urban areas by 2050, notes David Levinson, a transportation engineer at the University of Minnesota. “There’s a lot of urbanization left to happen,” Levinson says. “If planners imagine a city to take a particular form, but that’s not the way the city wants to behave, we’ll be making unwise investments.”

Barthelemy believes the model could also come in handy for estimating traffic delays, gas consumption and carbon dioxide emissions. “I think that this opens up the path to some really quantitative insights about cities,” he says. “We can take simple mechanisms, simple ingredients, and in the end predict how important properties are scaling with population.”

This article was originally published with the title “The Traffic Effect.”

Peer-to-peer car sharing gains momentum within rental car industry

I was interviewed by Catherine Boardman for the article Peer-to-peer car sharing gains momentum within rental car industry:

“Transportation analyst David Levinson said although traditional car-rental companies will not fade away, there is a niche for peer-to-peer services that can offer a quicker, easier alternative.

‘Apps can erode some of the hassle, and maybe today’s companies are too sclerotic to innovate,’ Levinson said.”

Accessibility and non-work destination choice: A microscopic analysis of GPS travel data


Congratulations to Dr. Arthur Huang for successfully completing and defending his dissertation: Accessibility and non-work destination choice: A microscopic analysis of GPS travel data

The advancements of GPS and GIS technologies provide new opportunities for investigating vehicle trip generation and destination choice at the microscopic level. This research models how land use and road network structure influence non-work, non-home vehicle trip generation and non-work destination choice in the context of trip chains, using the in-vehicle GPS travel data in the Minneapolis-St. Paul Metropolitan Area. This research includes three key parts: modeling non-work vehicle trip generation, modeling non-work, single-destination choice, and modeling non-work, two-destination choice. This research contributes to methodologies in modeling single-destination choice and multiple-destination choice and tests several hypotheses which were not investigated before.

In modeling non-work vehicle trip generation, this research identifies correlation of trips made by the same individual in the trip generation models. To control for this effect, five mixed-effects models are systematically applied: mixed-effects linear model, mixed-effects log-linear model, mixed-effects negative binomial model, and mixed-effects ordered logistic model. The mixed-effects ordered logistic model produces the highest goodness of fit for our data and therefore is recommended.

In modeling non-work, single-destination choice, this research proposes a new method to build choice sets which combines survival analysis and random sampling. A systematic comparison of the goodness of fit of models with various choice set sizes is also performed to determine an appropriate choice set size. In modeling non-work, multiple-destination choice, this research proposes and compare three new approaches to build choice sets for two-destination choice in the context of trip chains. The outcomes of these approaches are empirically compared and we recommend the major/minor-destination approach for modeling two-destination choice. The modeling procedure can be expanded to trip chains with more than two destinations.

Our empirical findings reveal that:

  1. Although accessibility around home is not found to have statistically significant effects on non-work vehicle trips, the diversity of services within 10 to 15 minutes and 15 and 20 minutes from home can help reduce the number of non-work vehicle trips.
  2. Accessibility and diversity of services at destinations influence destination choice but they do not exert the same level of impact. The major destination in a trip chain tends to influence the decision more than the minor destination.
  3. The more dissimilar the two destinations in a trip chain are, the more attractive the trip chain is.
  4. Route-specific network measures such as turn index, speed discontinuity, axis of travel, and trip chains’ travel time saving ratio display statistically significant effects on destination choice.
    Our findings have implications on transportation planning for creating flourishing retail clusters and reducing the amount of vehicle travel.

After working at Valparaiso University last year, he is currently teaching at the University of Minnesota Duluth.

Urban amusement parks |


Cross-posted at  Urban amusement parks:

“All the cool cities have urban amusement parks. In fact Minneapolis-St. Paul is the largest urban agglomeration in the upper Midwest without an urban amusement park.”

Urban amusement parks

Next to the originator of a good sentence is the first quoter of it” – Ralph Waldo Emerson Quotation and Originality 

Good artists copy, great artists steal.” – Pablo Picasso (attributed but unsourced)

One of the surest tests [of the superiority or inferiority of a poet] is the way in which a poet borrows. Immature poets imitate; mature poets steal; bad poets deface what they take, and good poets make it into something better, or at least something different. The good poet welds his theft into a whole of feeling which is unique, utterly different than that from which it is torn; the bad poet throws it into something which has no cohesion. A good poet will usually borrow from authors remote in time, or alien in language, or diverse in interest.” – Eliot, T.S., “Philip Massinger,” The Sacred Wood, New York:, 2000.

Good cities copy, great cities steal.” — Anonymous on Streets.MN

All the cool cities have urban amusement parks. In fact Minneapolis-St. Paul is the largest urban agglomeration in the upper Midwest without an urban amusement park.

Oh, you say, but the Greater MSP metropolis has ValleyfairNickelodeon Universe at theMall of America, the Midway and the Kidway at the State Fair, Comotown, and, coming soon, a Ferris Wheel at the old Psycho Suzi’s.

Valleyfair is suburban, the Midway and Kidway are seasonal, Como Town is in a large park fairly remote from the urban core, and the Mall of America, is, well, the Mall of America (though to be fair, it is more easily accessible by mass transit than anything but the State Fair).

2013-07-11 at 17-33-42

The history of Minneapolis and St. Paul includes many amusement areas that are no longer with us, including parks in Excelsior and Big Island on Lake Minnetonka, the short-livedWonderland in Longfellow, and Wildwood on White Bear Lake (Wildwood and Big Island were both owned by Twin City Rapid Transit as a way of better utilizing transit capacity).

Tivoli Gardens

What I am referring to are places like Chicago’s Navy Pier, Sydney’s Luna Park, the London Eye, or the best I have seen, Copenhagen’s Tivoli Gardens. They are walkable from the urban core or easily accessed by transit, and thus at least as geared to tourists as to residents. Tivoli and Navy Pier are fully programmed, so in addition to rides, there are numerous events so the sites are occupied day and evening much of the year. While Navy Pier has the scenery of Lake Michigan, Tivoli has no special natural advantage and is largely inward looking. Tivoli attracts about 4 million visitors per year. It is adjacent to a major railway station, helping attract visitors. My Tivoli photos can be seen on Flickr.

London Eye

View Map of Tivoli Gardens, Copenhagen


The site I have in mind is near Saint Anthony Main. This includes both vacant lots and industrial parcels that will eventually be reconfigured. We can start with the huge parking lot at 2nd Avenue and 2nd Street (and across the old Pillsbury Technology Center parking lot as well). I realize Metal-Matic is currently occupied by a business that employs people, but industrial sites in the city clearly have their days numbered as the value of land for other uses outweighs their use in manufacturing. We should be thinking about what comes next (without actually forcing them out). The site is adjacent to the freeway and the University, creating some built-in demand, as well as a short walk or NiceRide across the Stone Arch Bridge from downtown, catering to both the business and tourist crowd. These sites could become another 6-story stick frame apartment building, but it could be something more memorable.

Sydney - Darling Harbour Carousel

The land under the freeway could also be repurposed as part of this endeavor. There are lots of examples.

View Map of St. Anthony Main area

There are many other good sites, please identify some in the comments. The Metrodome would have been one, but it is to be reconfigured as something else.


I am trying to speak in a language public officials will understand. This does not imply an endorsement of this funding mechanism.

This lack of an urban amusement park constitutes a travesty that should be rectified with a TIF-financed economic development program as soon as possible. It has been shown bynumerous studies that urban amusement parks result in people spending money, which any macro-economist worth his salt-water will say is good for the economy.

OK, end of sarcasm. This doesn’t need to be a public facility. If it is popular, it should be able to pay for itself, like the State Fair. What it needs is to be enabled.



This is of course just speculation, a Fantasy-land so to speak. But with some vision, the cities should be able to attract an amusement park builder to create an attraction (or if Minneapolis gets one, St. Paul will want one too, so make that two attractions) that appeal(s) to the masses more than 8 nights a year.


Path dependence

If you don’t know where you’re going, any path will get you there.

Path dependence is the idea that where we are today depends critically on where we were yesterday. Some systems are path independent, those that have a single unique equilibrium. Finding the solutions to some math problems is independent of where you start, as long as you follow a particular algorithm.

However, most systems we deal with on a daily basis have some characteristics of path dependence. Where you live might depend on what job you took, which depends on what your previous job was and where you went to school, and a different decision anywhere along the way would change today’s position.

Nowhere is this more true than transportation. On the one hand, it is obvious that certain locations were destined to be important cities because of significant natural advantages. New York has a deep harbor at the confluence of major navigable river. Chicago is at the pivot point between vast agricultural lands to the Northwest and the shortest land path to the East Coast. It was natural railroads would flow through the point on the map we now call Chicago.

On the other hand, many city sites that were selected for natural advantages in one technological era (The Romans selected London and the Dutch and English chose New York in large part for their capability as ports), remain important even after that technology becomes obsolete. With the logistics revolution and the new dominance of container shipping, London’s shipping has moved northeast to Felixstowe as large container ships cannot easily ply the Thames, while New York’s shipping has migrated to the wide open spaces of New Jersey.

The one-time advantages result in a set of complementary investments and inter-related decisions that take on a life of their own. Because of local trading advantages, commodities markets, banks, insurers, and other related organizations located nearby. A critical mass of those institutions felt no need to migrate just because their initial raison d’être vanished. While a building is under construction, temporary framing will often be used until the more permanent structure is erected. Once the final building can stand on its own, the falsework is dismantled. In a sense, everything is falsework for what comes after.

This kind of mutual complementarity happens repeatedly in transportation. Airplanes are the perfect example of mobile capital. If Amalgamated Airlines no longer wants to serve a particular city pair, the airplane can easily be redeployed elsewhere. Yet 80 years into the commercial aviation industry, airlines today serve mostly the same hubs their predecessors did on the Airmail routes of the 1930s. American Airlines is still in Dallas, United in Chicago, Delta (Northwest) in Minneapolis, and so on.

While very few decisions are completely irreversible, transportation decisions come close. Where we place a right-of-way, or an airport will explain where that facility will be decades, or even centuries from now.

A slight deviation from the efficient path to solve a short term problem today will cost travelers time for years to come. It is important to get the design right for the long term. (Undoubtedly this has social costs, see e.g. I-94 through the Rondo in Saint Paul).

But a slight deviation from the path will also change what the long term is. Build a bridge “here” rather than “there”, and then you will adjust all of the roads feeding into the bridge to meet it “here” (instead of “there”). And then land will be developed along the road to “here” to take advantage of the newly created accessibility, properties will be platted, buildings will be built, travel and trade patterns established, and other critical dependencies will come to assume that the bridge is “here”. At some point, say 50 years in the future, the bridge will need to be replaced. Even if “there” was a better location than “here” initially, after five decades of adaptation, it is quite likely that “here” is better now. The whole may have been better were a different initial decision been made, given conditions at the time. Given current realities, that path must now be foregone.

In transportation we say build it right the first time, because there won’t be a second chance. And that is true. But also remember the world will adapt to whatever we do, and we cannot let the perfect be the enemy of the good.