Hao Wu, Paolo Avner, Genevieve Boisjoly, Carlos K. V. Braga, Ahmed El-Geneidy, Jie Huang, Tamara Kerzhner, Brendan Murphy, Michał A. Niedzielski, Rafael H. M. Pereira, John P. Pritchard, Anson Stewart, Jiaoe Wang, and David Levinson (2021) Urban access across the globe: an international comparison of different transport modes. NPJ Urban SustainabilityVol. 1, Article 16 [doi]
Access (the ease of reaching valued destinations) is underpinned by land use and transport infrastructure. The importance of access in transport, sustainability, and urban economics is increasingly recognized. In particular, access provides a universal unit of measurement to examine cities for the efficiency of transport and land use systems. This paper examines the relationship between population-weighted access and metropolitan population in global metropolitan areas (cities) using 30-minute cumulative access to jobs for 4 different modes of transport; 117 cities from 16 countries and 6 continents are included. Sprawling development with intensive road network in American cities produces modest automobile access relative to their sizes, but American cities lag behind globally in transit and walking access; Australian and Canadian cities have lower automobile access, but better transit access than American cities; combining compact development with an intensive network produces the highest access in Chinese and European cities for their sizes. Hence density and mobility co-produce better access. This paper finds access to jobs increases with populations sublinearly, so doubling metropolitan population results in a less than double access to jobs. The relationship between population and access characterizes regions, countries and cities, and significant similarities exist between cities from the same country.
The City vs. Country mismatch (where we plan for transportation systems seemingly independent of the context: city or country (suburb)) is especially relevant in metropolitan areas constructing expensive medium and high capacity transit lines to presently undeveloped places, or (re-)constructing and widening freeways in the midst of core cities.
If we are building a city, that means focusing resources closer to the center than the edges, since that is where more of the growth will be.
So the question arises in Minnesota: Are we building a city in the Minneapolis-St. Paul region or not?
Some would argue the region is already a city. Clearly the downtowns and some nearby areas resemble cities. But much if not most of the population lives in single family homes with a yard. Not there is anything wrong with that, but that yard increases spacing between neighbors, lowers densities, and makes it harder to operate a successful transit system in the automobile era.
The decisions we make regarding transportation investment rest on what our collective vision is for this place. If we are building a city, going “all in” on transit is a lot more sensible than if we are not, and a lot more sensible than half-measures. If we are not, going even partly in on fixed rail transit is fairly pointless.
The evidence to date is fairly mixed. The region is growing at about 1 percent or so per year in population. That is a bit under 30,000 people or so per year. (Investing in transit will not put a measurable dent on this, as it is hard to imagine it either increasing or decreasing the birth or death rate noticeably or significantly affecting migration patterns).
Where are those people going? Most of them are not being added to the center. If all of them were added to Minneapolis and St. Paul proper, the populations of the core cities would rise from 667,000 in 2010 to about 950,000 in 2020. If more than half of them were added to the core cities, their population would be around 810,000. Current forecasts suggest the population of the core will be closer to 732,000. In other words, well more than half (around 80%) of the region’s growth remains outside the core cities, and not terribly urban. While the center is projected to grow at a faster rate than the edges, it is not growing faster in absolute numbers.
This region collectively much more resembles Broadacre City than Greenwich Village, and probably more Broadacre City than even Welwyn Garden City or Letchworth. While the density at the edges after development must (by definition) be higher than before development, the average experienced density (e.g. the population-weighted density) may continue to fall as the region expands.
In this dispersed suburban landscape, point-to-point transportation predominates.
In the not-quite-a-city urban areas, point-to-point transportation still predominates.
It is only in full-fledged dense cities (the level of density required depends on income, technology, and other factors), and dense cities that sustain, that full-fledged dense (fixed route, fixed infrastructure) transit is warranted. Loosely, the transit-city threshold is on the order of 10,000 persons per square mile, sustained over some region. This implies a Minneapolis population of 540,000 and a St. Paul population of 520,000. While those numbers are achievable in principle, they require significant changes in market demand and reduction in supply constraints to achieve. If it were to be achieved, still under 1/3 of the region would be in the transit city. The remainder would be the country, or its suburban simulacrum.
Certainly, some parts of the core cities already sustain this density, and there is no requirement that all of the core city achieves the density, just that a sufficiently large part does. Most doesn’t.
For the Metropolitan area, fixing the total space, this threshold implies a population of 63 million, or relaxing the space but fixing the population, a shrinkage to a developed area of 345 square miles. I would consider either outcome highly unlikely.
The car-free lifestyle is sufficiently uncommon that the local newspaper does a feature on it.
In less dense cities, less transit is warranted. But if the transit is insufficiently dense (in space (coverage) and time (frequency)), anyone with a choice will anchor to the on-demand, point-to-point mode, which will be sufficiently faster to outweigh any additional expense
Creating Transitopolis: the Transit City
Building the transit city (Transit-opolis) requires most of the region’s central city residents (20% today) to willingly abandon the automobile in the first place: creating an environment where car ownership can be voluntarily foregone because it is to the benefit of all concerned not to own the car. The more transit users there are, the better the transit service is, in a virtuous cycle. (And of course, the fewer transit users there are, the worse the service, in a vicious cycle).
This implies focusing transit investments in the central cities, and not diffusing scarce capital like peanut butter across the region.
Why can’t we have the best of both worlds? There are a variety of interim or transitional strategies
Park and ride lots accessed by private car may serve the center-working/surburban-living suburbanite, which transfer the worker to a radial transit route. This serves a small fraction of workers, since most people don’t work downtown, where these radial services terminate, and the frequencies are typically not high enough (especially mid-day) to rely on for anyone with irregularity in their life.
Single Car households with multiple workers splits the difference, where presumably at least one of the workers does not use a car for travel to work, or the two workers carpool to the same location. This is certainly the most common hybrid case.
Weekend Car households in which the work trip is conducted by walking, biking, or transit, and the car is used for the weekend and special trips.
Car sharing (on-demand car rental) allows the car-less transit user to have a car when needed for the less frequent trips. Taxis (and so-called ride-sharing services) serve a similar function.
These attempts at melding can serve specific niches and are potential transitional steps to the transit city, in that it is more likely to give up a car for some trips than all trips, or portions of trips than all of the trip. They are not however the end state.
My own prediction is that we are not in fact building a transit city. The densities that will emerge in Minneapolis and St. Paul in the next 20 or 30 years are insufficient to support a transit-based city for a majority of residents of even the core cities. (And, simultaneously and not coincidentally, the transit investments are insufficient to support a city where most people are car-less).
This explains my pessimism about the use of expensive (high fixed cost) city transit tools now. The right decision if you are certain you are building a transit city (or already live in one) is different from the decision if you are not.
While it is argued that never making the investments will ensure the transit city does not emerge, we can continuously ratchet up, rather than doing it in enormous steps. Not investing now does not mean never investing. “No” is reversible (in other words, “no” does not mean “no”).
On the other hand, “yes” is irreversible for a long time. But making the investment does not guarantee the transit city will emerge, plenty of cities, including our own, have invested in rail without seeing accompanying development, leaving an enormous pale proboscidea in its place.
My own prediction is that the core cities of Minneapolis and St. Paul are on a path towards Transitopolis. The necessary population densities to support transit are within striking distance, especially in Minneapolis, and the leadership of both cities is keen on achieving that. The big question is whether the demand for higher density housing is there in the cities, and with changing demographics, preferences, and technologies, the demand for suburban lifestyle is diminishing relative to that for urban living. Most people won’t spend their entire lives in either suburban harmony or at an urban tempo, but rather migrate between the two over the years.
The investments in the cities to support transit at a level that most people can avoid the car for most trips are still too low to make this work, there is a marked lack of ambition on the part of regional transportation officials to serve the transit cities they are building with actual rapid transit. This dysfunction has several causes, not the least of which is the leadership of planning organizations that don’t use the modes they manage, which we can attribute to the strange politics of regional organizations.
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.
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.
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).
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).
Are accessibility and mobility complements or substitutes? I have a mental model a graph with a y-axis as density, and x-axis as mobility, where the Northeast corner would be high access: high density multiplied by high mobiilty.
This system behaves differently by modes. For transit, cities arrange themselves on a line from the southwest to the northeast (a positive feedback loop between supply and demand). For auto cities arrange on a line from the southeast to the northwest (a negative feedback loop between congestion and demand). Using data one could place specific cities on the graph. One expects places like New York and Hong Kong in the northeast corner, most US cities in the southeast corner, small developing-world cities without widespread adoption of modern automobile or transit technology in the southwest corner. Depending on where you draw the threshold, it is hard to see too many places in the upper northwest corner, as it would be difficult to grow to have high density without mobility. (Why would the city grow without the accessibility advantages?)
Accessibility is a good, but it is not a good without costs, and there are limits to how much people are willing to pay for access. It may also suffer from diminishing returns, beyond a point each unit of accessibility is worth less and less. Places like Minneapolis have yet to reach that point, but surely there are places that have.