Accessibility and the Ring of Unreliability

Recently published:

Abstract: This study measures the variability of job accessibility via automobile for the Minneapolis – St. Paul, Minnesota region. The accessibility analysis uses cumulative opportunity measures. The travel times on the network are tested at 10th, 50th, and 90th percentile speed drawn from an annual average for each link from GPS speed data for 2011. It is shown that accessibility varies widely with travel speed. Some parts of the region (a ring around the core) have more volatility in access to jobs (and are thus less reliable) than others.

Keywords: AccessreliabilityvulnerabilityGPS

Newark International Airport to New York City by Trains

On a recent trip to New York, I went through Newark (Liberty!) International Airport. My previous experience here has only been changing planes. It was not a good experience, nearly missing my flight to Paris, (the doors had closed) due to delays on the first leg,  but saved because the second leg was subsequently delayed too, and a quick-thinking ground agent saw me milling about trying to figure out another connection, and reopened the doors.

This time was simpler. The flight was delayed 40 minutes from Minneapolis – St. Paul due to air traffic control (no big deal), and we got in more or less on time, because that’s how big the buffer is now. The terminal was crowded. My plan was to take the train into New York City since I was staying at a hotel near Penn Station (New York). I learned there was also a Penn Station (Newark) which I am sure is needlessly confusing.

So exiting the secure area, and going to ground transport is a long walk. It always seems longer when you are unfamiliar. Nevertheless I figured out to take the AirTrain to the Amtrak/NJ Transit station.

Before boarding AirTrain I purchased tickets at the kiosk, which had a short line, but seemed straight-forward enough (compared to many of these things). The human monitoring people buying tickets from the machines (because??? [because the user interface is bad, because jobs]) kept reminding people they could buy tickets at the actual train station. No one actually left their position in line.



AirTrain, the airport inter-terminal shuttle system (a monorail) had its own issues, not departing for 5 minutes. The station was leaking due to recent rainstorms, the towels on the floor indicating a duct-tape solution to declining infrastructure. We got to the penultimate station, and they ordered us out and transferred to the AirTrain on the other track to make the final leg to the slightly off-airport Airport Station. Once we got there, it was another 9 minute wait for a train, no big deal. Real estate at Newark is not scarce, it is surrounded by  surface rather than structured parking lots. There are plans afoot to renovate AirTrain.

The train ride through the swamps of Jersey, into Seacaucus, and then under the River to Manhattan was sluggish but largely uneventful. There were a few minor delays and stops, but no major problems. There are plans afoot to build a new tunnel under the Hudson.

NJ Transit has its station at Penn Station, but in a separate building from the more (in)famous station under Madison Square Garden. There are a variety of proposals afoot to give Penn Station a more magnificent front end. I remind everyone that arrivals into the city see the backend of the station, not its front.

One day, maybe, maintenance will be taken seriously, and infrastructure will be built, and New York, the city in America most deserving of well-maintained high quality intercity rail will finally get it.


Meditations on Metrorail and Maintenance

I recently had the opportunity to ride Washington DC’s Metrorail system. I first rode it the year it opened (1976), and as a child of  nearby central Maryland, recall taking the Red Line to the Bicentennial Celebration on July 4th on the National Mall (we parked remotely and used the line to get in, I think we walked back to the car). I was 9, and it seemed the future, all modern and sterile.

photo_101105_014Now it is the past’s version of the future, modern in a post-modern age, dim and decaying, and still sterile.

My subjective impressions are such that it is a system I avoid, taking it only from the airport to my hotel when I am in DC for a meeting or conference.

From a simply sensory perspective, it makes me feel nauseous in a way that other similarly aged systems (BART, MARTA) never did, much less more modern light rail lines or other older subways (London, New York, Paris). I don’t know what it is about the acceleration and braking, the wobble to the left and right, but it is just unsettling. I have not actually lost it on the Metro, but damn I am relieved to get off.

It also has a distinct smell, and unlike Bobby Duvall’s claim of Napalm, it is not the smell of victory. All cities have characteristic odors. Blindfolded you can often know if you are in Washington, New York, San Francisco, or Minneapolis. My memories of DC are tainted by the parfum d’Metro.

The  delays, in large part due to a recent crash maintenance and repair program, have not affected me as a non-resident, but I can imagine this would be infuriating to locals.



Sure safety first, but one has the impression of Maintenance Theater about the way this was rolled out, shutting the entire system one day, rather than one line a day with appropriate substitute Metrobus service. I suppose it worked as such, and certainly Washingtonians are now resigned to this. It’s too bad it couldn’t be properly maintained all along, but that is the general problem we historically nomadic humans have, maintenance is not in our collective genetic or cultural memory. We build, we abandon, we move, repeat.

Once you live long enough, you see the new futuristic things of your youth fade into decline. Infrastructure, unlike life, does not self-renew. It requires humans to be the hand-maidens who bring about renewal. And in modern human culture we prize the new, not the renewed. Infrastructure generally doesn’t get too much attention. When it does, the ribbon-cutting is “above the fold” in newspaper-speak. Catastrophic failures are, in a bad way, too. But the politician always claims credit for the ribbon-cutting and shifts blame for the failure. Changing the culture to prize maintenance and punish the acquisition of new toys until the existing ones are cared for is a shift for the ages. I don’t see how it is promulgated, though conferences like The Maintainers and groups liks Strong Towns seem to be trying.

Goodbye, Car2Go; what’s next for car-sharing? | Star Tribune

Janet Moore in the Star Tribune writes Goodbye, Car2Go; what’s next for car-sharing? She quotes the blog:


After Car2go’s announcement, University of Minnesota Prof. David Levinson wrote in his Transportist blog that in order for car-sharing to work, “access costs must be low, generating demand, which will increase vehicle availability (as suppliers respond to demand), which will lower access costs, which will increase demand.”

Levinson said that the existing Car2Go fleet could have accommodated more customers (Car2Go has 400 vehicles and about 29,000 members in the Twin Cities). He also points out that with gas prices so low and the economy relatively strong, people can readily drive and buy their own cars.

See the original post: Car2Gone: On the decline of Carsharing in the late 2010s.

The Transportist – Newsletter – November 2016

NPR Here & Now – The Economics For And Against Trump’s Infrastructure Plan

I will be on NPR’s Here & Now on today’s episode talking infrastructure.

One area where Democrats are hoping to work together with President-elect Donald Trump is infrastructure.

Before he was elected, the Trump team put out a proposal for infrastructure that would include public-private partnerships and tax credits for companies to invest in roads, bridges and more.

Here & Now‘s Robin Young speaks with University of Minnesota professor David Levinson (@trnsprtst) about the economic arguments for and against such a plan, and why infrastructure shouldn’t be thought of as a jobs program. Levinson is also author of the book “The End of Traffic,” and writes the Transportist blog.

Update: Audio Available (download) or stream

U study says transit does not have impact on public health

While many click-bait articles have headlines that claim using public transportation has a significant impact on health, a University of Minnesota study, which explored the correlation between transit and public health, found that there was no significant evidence showing that using public transit improves health.

“For the last 10-15 years, people have been saying they want people to be walking or using transit because there is a significant health benefit,” said David Levinson, University transportation studies senior research associate and co-author of the study.

“It may or may not be true, but it’s a very weak correlation.”

There is an idea that commuters are a more healthy population due to the fact that they use public transit, Levinson said.

Transit is often associated with walking or biking. Previous studies have found that citizens in areas with more transit options have a lower BMI.

But using BMI for that conclusion doesn’t account for commuters who may eat fast food every day or substitute buses and trains for walking from place to place, Levinson said.

Ultimately, the researchers found transit did not have a significant impact on public health.

Alireza Ermagun, University urban and regional planning Ph.D. candidate  [sic – he got a PhD in Civil Engineering, he was also a MURP] research assistant and co-author of the study, said he wanted to point out problems with associating insignificant correlations to data and making assumptions not backed up by sufficient research.

Researchers often rely on data they already have to draw conclusions because research is expensive and difficult to compile, he said.

For example, the researchers analyzed the height of transit users relative to their location because other researchers often correlate travel method and body mass index. They found that people were shorter in locations like cities, where transit was more readily available.

This could justify the claim that transit makes you shorter, he said.

“People are too quick to use these results to draw conclusions,” Levinson said.

But Ermagun said he hopes this study will caution future researchers from making assumptions about their data based on exaggerated connections.

“The result of this study helps people gain a clearer view,” he said. “It allows them to put these resources in a more effective direction.”

Elizabeth Wrigley-Field, [ed. note, apparently a real person] sociology assistant professor, said researchers often try to narrow down one specific way to improve public health.

“There is a lot of tendency in the topic of health to focus endlessly on things that actually make a small difference,” she said. “Like exactly what fruit we should be eating or what exercise we should be doing.”

Instead, Wrigley-Field said promoting larger-scale research would be a more efficient means to improving health through initiatives like reducing air pollution, combating poverty and eliminating food insecurity.

“The relative lack of attention to these topics isn’t a lack of knowledge,” she said, “but a lack of political will to talk about them.”

Elements of Access: Hierarchy

In binary networks, the focus is on whether or not a connection between two nodes exists.  However, not all links (or nodes) are created equal, particularly when it comes to transportation networks.  When we know about the presence of a link as well as the strength of that link, it is called a valued network.  For instance when traveling from A to B in a street network, there is usually discontinuity in street type.  In other words, one might move from a local street to a collector road to an arterial road and then back to a collector before reaching their destination.  While engineers know this sort of differentiation as functional classification, it is also referred to as hierarchy.


Hierarchy, which is embedded in many natural and societal systems such as biologic cells and the Internet, is a common transportation complexity that requires a more complicated topological analysis (Tomko, Winter, & Claramunt, 2008).  Typical topological measures such as Degree or Betweenness can be useful in helping understand network hierarchy, particularly in tree-like networks; however, such measures would fail to properly distinguish between streets in a gridded street network.  In the above version of Metropolis’ street network, the major streets are represented by thicker lines and easily discerned, even in a gridded network (Fleischer, 1941).   Using the basic set of topological metrics, we would have no idea that 8th Street is functionally different from 7th Street or F Street from D Street.  These metrics fail to consider attributes – such as urban design, number of lanes, active transportation infrastructure, adjacent land uses, and speed – beyond network structure and would not necessarily be able to distinguish such streets.


Working with hierarchical networks often involves dividing networks in multiple layers or tiers.  Measurements of heterogeneity have also become common proxies for characterizing hierarchy.  To identify heterogeneity among street segments, researchers have used entropy measures as well as discontinuity measures (Xie, 2005).  Discontinuity, for example, does not necessarily denote a disconnected network; rather, the reference is to the discontinuity in moving from one street type to another.  If we sum the number of times a traveler goes from one type of street to another while traveling along a shortest path route, we find the trip discontinuity.  Dividing that number by the length of the trip gives us the relative discontinuity (Parthasarathi, 2011).  Other simplistic hierarchy measures calculate the relative percentage of a particular type of road.  For instance, we might divide the number or length of arterials by the total number or length of roads to find the relative percent arterials (Parthasarathi, 2011).


Interestingly, it is not uncommon for large-scale transportation models to delete streets on the lower end of the hierarchical spectrum (i.e. local streets) for the sake of computational efficiency.  Yet, removing such streets creates a bias against more connected networks because less connected networks typically need to be supported by major streets with more capacity than would be needed in more connected networks (Bern & Marshall, 2012).  Some topological researchers – where the focus should be on understanding the full network – unfortunately reach the same conclusion: “urban streets demonstrate a hierarchical structure in the sense that a majority is trivial, while a minority is vital” (Jiang, 2009).  If we only care about vehicle traffic flow, such statements may be true.  However, my previous street network research confirms that understanding the full network holds the key to pushing toward improved safety, increased active transportation, and better environmental and health outcomes (Bern & Marshall, 2013; Marshall & Garrick, 2009, 2010a, 2010b, 2012).

Toronto looks at toll roads

Oliver Moore at the Globe and Mail writes “Dynamic tolling could be the key to ease congestion while raising money“. The money quote is below:

Still, the consensus from people who study tolling is that what Toronto is discussing now has the potential to be a good start.

“I’d view it as sort of a phased thing, and this is the first step,” said David Levinson, a transportation analyst and professor in the civil engineering faculty at the University of Minnesota, who has researched road pricing. “It’s much easier to move from a toll to a toll with differentiated time of day prices than it is to move from no toll to tolling.”


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