Why don’t more city transport networks use “through-routing”?

The Parisian RER network is one of the few suburban rail systems that does use through-routing. Image: Metropolitan/Wikimedia Commons.

Through-routing means that a route designed to carry people to or from a downtown doesn't end in the downtown; instead, it flows across downtown and out the other side as a different route.

In Alon Levy's vision of New York area commuter rail, for example, the trains flowing into Manhattan from Connecticut (red on the map below) would flow through the city and out onto southern lines in New Jersey and vice versa. Through-routing means that downtown is in the middle of a line, not at the end. You can do the same thing with any kind of radial transit service, bus or rail. (Editor’s note: Paris’ RER networks, or London’s Thameslink or Crossrail, are similar examples.)

Alon Levy's regional rail plan for New York, originally published and explained on The Transport Politic.

Through-routing has four colossal advantages:

Some people are actually going from Connecticut to New Jersey, for example, and through-routing lets them make this trip without changing trains. More commonly, a lot of people from the north (i.e. Connecticut) are going to southern parts of New York City, while a lot of other people from New Jersey are going to northern parts of the city: a through-routed system serves both groups, which are briefly on the train at the same time in the city.  

Because of the decentralised structure of Paris, lots of Parisians are riding across the city to the far side, in both directions, so the RER's through-routed structure is absolutely essential to avoid forcing huge masses of people to change trains. 


  • Reduced need for terminus facilities on expensive downtown real estate, and thus potential for higher frequency.

Ending a line downtown means having facilities to store a bus or train for at least a few minutes, consuming expensive space.

Trains typically reverse direction at an end-of-line station, so the driver needs to close her cab, walk the length of the train, and get herself set up on the other cab; she may also be entitled to some break time. A train occupies one of a limited number of tail tracks while this is happening, so this function becomes the limiting factor on the frequency of the whole line. And downtown, there are lots of physical and cost constraints on station design, so you almost never have as many tail tracks as you'd like.

Buses need space to turn around and their drivers, too, are entitled to some break time at the end of a trip – so end-of-line stations on frequent services need space for a number of buses to pile up in a first-in-first-out queueing arrangement. All this takes a lot of space, and this space is a lot cheaper at the end of a suburban line than it is in the middle of downtown. 

  • Fewer line ends, for reduced operating and capital cost.

The time it takes to turn a bus or train around, and provide the driver break, is usually not related to the length of the line. Through-routing two routes eliminates two ends-of-lines, which reduces the cost, both operating and capital, of those inefficient turnaround movements. Often, through-routing two lines actually reduces, by one or two, the number of buses or trainsets required.    

  • Fewer vehicles downtown providing the same service.

Sometimes, too, the pre-through-routed lines overlap in downtown, so the through-routing eliminates that overlap. Instead of having a bus dropping off passengers interacting with another bus picking passengers up, you have one bus dropping off passengers and picking them up at the same time. For buses especially, downtown street capacity is a very limited resource in big cities, and through-routing helps economise on it.

So why isn't there more of through-routing? Here are five reasons.

  • Unbalanced markets on the two sides of downtown.

There's never an exact one-to-one match between routes approaching from one direction and those approaching from the opposite direction.

For example, San Francisco's downtown is on the bay at the northeast corner of the city – so there are no routes extending north and east that could be paired to routes flowing south and west. To the extent that such through-routes have been created (e.g. San Francisco's Muni Metro T line) the result is a circuitous approach to downtown for one of those lines.  

  • Excessive line length.

The probability that your train or bus is delayed is directly related to how long it's been running since it last had an end-of-line break. (When a vehicle arrives late at the end-of-line, its break time is reduced, so that it can leave on time, or at least not as late.)

Through-routing makes lines longer, so it can compound this problem. This is obviously more of an issue in services that are exposed to more causes of delay, such as services in mixed-traffic and services with driver-administered fare collection.

  • Jurisdictional barriers.

There are plenty of cases where through-routing would be in order but the two sides of downtown are different jurisdictional turf. They may be different states, as in New York, or different transit agencies.

In the UK and Australia, they may be different private operating companies – and although both are government-subsidised, UK/Australia governments tend to defer to private companies about network design, so you often get designs that reflect company turf boundaries rather than efficient use of subsidies or meeting the needs of the customer. (London is an exception; some Australian states are also working on this problem.)


  • Infrastructure barriers.

Your great-grandparents' jurisdictional barrier is often your infrastructure barrier, and New York City is the obvious example. Because each commuter rail line was designed by a separate entity, and each of these entities was thinking only about getting people into Manhattan, the terminal stations are not physically connected in the way you'd need in order for trains to flow through.

This is the cause of most of the capital expense in Alon Levy's proposal for New York above.

  • They just haven't thought of it.

If your transit agency has non-through-routed lines, and you can't figure out why, send them a link to this post – and ask them.

Jarrett Walker is an international consultant in public transit network design and policy, based in Portland, Oregon. He is also the author of  “Human Transit: How clearer thinking about public transit can enrich our communities and our lives”, which you can buy here.

This article was originally written for his blog in 2009, and is reposted here with permission.

 
 
 
 

Urgently needed: Timely, more detailed standardized data on US evictions

Graffiti asking for rent forgiveness is seen on a wall on La Brea Ave amid the Covid-19 pandemic in Los Angeles, California. (Valerie Macon/AFP via Getty Images)

Last week the Eviction Lab, a team of eviction and housing policy researchers at Princeton University, released a new dashboard that provides timely, city-level US eviction data for use in monitoring eviction spikes and other trends as Covid restrictions ease. 

In 2018, Eviction Lab released the first national database of evictions in the US. The nationwide data are granular, going down to the level of a few city blocks in some places, but lagged by several years, so their use is more geared toward understanding the scope of the problem across the US, rather than making timely decisions to help city residents now. 

Eviction Lab’s new Eviction Tracking System, however, provides weekly updates on evictions by city and compares them to baseline data from past years. The researchers hope that the timeliness of this new data will allow for quicker action in the event that the US begins to see a wave of evictions once Covid eviction moratoriums are phased out.

But, due to a lack of standardization in eviction filings across the US, the Eviction Tracking System is currently available for only 11 cities, leaving many more places facing a high risk of eviction spikes out of the loop.

Each city included in the Eviction Tracking System shows rolling weekly and monthly eviction filing counts. A percent change is calculated by comparing current eviction filings to baseline eviction filings for a quick look at whether a city might be experiencing an uptick.

Timely US eviction data for a handful of cities is now available from the Eviction Lab. (Courtesy Eviction Lab)

The tracking system also provides a more detailed report on each city’s Covid eviction moratorium efforts and more granular geographic and demographic information on the city’s evictions.

Click to the above image to see a city-level eviction map, in this case for Pittsburgh. (Courtesy Eviction Lab)

As part of their Covid Resource, the Eviction Lab together with Columbia Law School professor Emily Benfer also compiled a scorecard for each US state that ranks Covid-related tenant protection measures. A total of 15 of the 50 US states plus Washington DC received a score of zero because those states provided little if any protections.

CityMetric talked with Peter Hepburn, an assistant professor at Rutgers who just finished a two-year postdoc at the Eviction Lab, and Jeff Reichman, principal at the data science research firm January Advisors, about the struggles involved in collecting and analysing eviction data across the US.

Perhaps the most notable hurdle both researchers addressed is that there’s no standardized reporting of evictions across jurisdictions. Most evictions are reported to county-level governments, however what “reporting” means differs among and even within each county. 

In Texas, evictions go through the Justice of the Peace Courts. In Virginia they’re processed by General District Courts. Judges in Milwaukee are sealing more eviction case documents that come through their courtroom. In Austin, Pittsburgh and Richmond, eviction addresses aren’t available online but ZIP codes are. In Denver you have to pay about $7 to access a single eviction filing. In Alabama*, it’s $10 per eviction filing. 

Once the filings are acquired, the next barrier is normalizing them. While some jurisdictions share reporting systems, many have different fields and formats. Some are digital, but many are images of text or handwritten documents that require optical character recognition programs and natural language processors in order to translate them into data. That, or the filings would have to be processed by hand. 

“There's not enough interns in the world to do that work,” says Hepburn.


Aggregating data from all of these sources and normalizing them requires knowledge of the nuances in each jurisdiction. “It would be nice if, for every region, we were looking for the exact same things,” says Reichman. “Instead, depending on the vendor that they use, and depending on how the data is made available, it's a puzzle for each one.”

In December of 2019, US Senators Michael Bennet of Colorado and Rob Portman of Ohio introduced a bill that would set up state and local grants aimed at reducing low-income evictions. Included in the bill is a measure to enhance data collection. Hepburn is hopeful that the bill could one day mean an easier job for those trying to analyse eviction data.

That said, Hepburn and Reichman caution against the public release of granular eviction data. 

“In a lot of cases, what this gets used for is for tenant screening services,” says Hepburn. “There are companies that go and collect these data and make them available to landlords to try to check and see if their potential tenants have been previously evicted, or even just filed against for eviction, without any sort of judgement.”

According to research by Eviction Lab principal Matthew Desmond and Tracey Shollenberger, who is now vice president of science at Harvard’s Center for Policing Equity, residents who have been evicted or even just filed against for eviction often have a much harder time finding equal-quality housing in the future. That coupled with evidence that evictions affect minority populations at disproportionate rates can lead to widening racial and economic gaps in neighborhoods.

While opening up raw data on evictions to the public would not be the best option, making timely, granular data available to researchers and government officials can improve the system’s ability to respond to potential eviction crises.

Data on current and historical evictions can help city officials spot trends in who is getting evicted and who is doing the evicting. It can help inform new housing policy and reform old housing policies that may put more vulnerable citizens at undue risk.

Hepburn says that the Eviction Lab is currently working, in part with the ACLU, on research that shows the extent to which Black renters are disproportionately affected by the eviction crisis.

More broadly, says Hepburn, better data can help provide some oversight for a system which is largely unregulated.

“It's the Wild West, right? There's no right to representation. Defendants have no right to counsel. They're on their own here,” says Hepburn. “I mean, this is people losing their homes, and they're being processed in bulk very quickly by the system that has very little oversight, and that we know very little about.”

A 2018 report by the Philadelphia Mayor’s Taskforce on Eviction Prevention and Response found that of Philadelphia’s 22,500 eviction cases in 2016, tenants had legal representation in only 9% of them.

Included in Hepburn’s eviction data wishlist is an additional ask, something that is rarely included in any of the filings that the Eviction Lab and January Advisors have been poring over for years. He wants to know the relationship between money owed and monthly rent.

“At the individual level, if you were found to owe $1,500, was that on an apartment that's $1,500 a month? Or was it an apartment that's $500 a month? Because that makes a big difference in the story you're telling about the nature of the crisis, right? If you're letting somebody get three months behind that's different than evicting them immediately once they fall behind,” Hepburn says.

Now that the Eviction Tracking System has been out for a week, Hepburn says one of the next steps is to start reaching out to state and local governments to see if they can garner interest in the project. While he’s not ready to name any names just yet, he says that they’re already involved in talks with some interested parties.

*Correction: This story initially misidentified a jurisdiction that charges $10 to access an eviction filing. It is the state of Alabama, not the city of Atlanta. Also, at the time of publication, Peter Hepburn was an assistant professor at Rutgers, not an associate professor.

Alexandra Kanik is a data reporter at CityMetric.