Tag Archives: rapid transit

I can’t believe I’m writing a post on Personal Rapid Transit!

Morgantown WV PRT System, as seen from Google Streetview

Morgantown WV PRT System, as seen from Google Streetview

Reading through the history of the personal rapid transit (PRT) on the Verge by Adi Robertson, I couldn’t help but think of the similarities with many familiar projects. Cost overruns, scope creep, politics, government red tape, all conspiring to erode the value of an otherwise promising concept.

First, you can’t write about PRT without acknowledging the inherent geometric flaw of the concept: it can’t scale. Jarrett Walker frequently talks about the fundamental geometry of transit, and succinctly explains the geometric flaw of PRT:

Bottom line:  When “personal rapid transit” succeeds, it succeeds by turning into a conventional fixed route transit system.  The fantasy of “personal” transit is that a vehicle will be there just for our party and take us directly to our destination, but in constrained infrastructure this only works if demand is low.  But PRT was meant to the the primary transport system in a car-free city, so demand would be high.  It was never going to work.

This is also true of the Morgantown, WV PRT system, which makes use of different operating modes. During times of high demand, it operates as a fixed route transit system between the busiest stations; during low demand periods, cars stop at every station, regardless of demand.

Mass transit might be an out of fashion descriptor, but it helps illustrate transit’s scalability. Good transit doesn’t just move large masses of people, it requires mass to succeed. ‘Personal’ transit rejects the masses; it also requires expensive infrastructure to inefficiently move people.

Robertson skirts around the geometric limitations of PRT as a concept, but never appropriately douses the concept with cold water. Any history of PRT must focus on the Morgantown, WV system. Any article about PRT will inevitably draw comparisons to current research on driverless cars. Comparing the two exposes the conceptual flaw:

Self-driving vehicles, he points out, wouldn’t have taken cars off Morgantown’s crowded roads — at least, not in the same volume. As long as they’re intermingled with human-driven cars, they can’t run with the same centralized efficiency. And once you start thinking about the obvious solution — a dedicated lane for self-driving cars — you might start running into the same problems as PRT.

Leaving aside PRT’s conceptual flaws, Robertson’s history of the concept echoes common challenges in the American history of infrastructure projects: shifting government mandates, political interference, procurement regulations, and so on. Some highlights:

Goals for transit: Robertson documents the history of federal funding for PRT, with the Urban Mass Transit Administration providing research grants to explore the concept.

The focus on new technology in transit often meant unnecessarily reinventing the wheel (see BART’s broad gauge track), but also exploring new concepts like PRT. New concepts are sexy, even attracting the direct interests of President Nixon:

His mantra, as Alden puts it, was that if “Kennedy can get a man on the Moon, I can get a man across Manhattan.”

Lack of clarity about the UMTA’s goals for the program help add to the confusion. Is the goal to provide effective transit, or to prove a new technology/concept? Crosstown transit is a practical goal, but it doesn’t require big technological innovations. Landing on the Moon is an impractical goal that wasn’t possible without new technologies – and the moonshot analogy makes it easy to conflate two different goals.

From the start, there’s tension between researching new technologies and practical, proven, cost-effective projects. Many PRT boosters in West Virginia were approaching this a big experiment; the government bureaucrats wanted a functioning system. Once the system proved more conventional than revolutionary, Robertson notes, “the age of experimentation was over.”

Politics: Robertson also shows the competing interests of the various parties involved in funding and executing the Morgantown project. West Virginia University approached PRT as an experiment, while UMTA wanted a more practical proof of concept – something that could be built elsewhere if successful. On top of these turf battles, President Nixon wanted a completed project to include in his re-election campaign materials, pressuring the team to complete things before they were ready.

Procurement and red tape: As WVU championed the PRT project, they looked for federal funds to offset the cost. Then, as now, those dollars had strings attached. UMTA required a NASA JPL redesign of the vehicles; one of the independent engineers took patents to established defense contractor Boeing in order to better compete in project bidding.

Right of way: The single most important element of the Morgantown PRT system is the elevated guideway. Complete grade separation from the traffic at street level and the interference from cars, bikes, and pedestrians not only speeds travel, but made PRT’s automated operation possible (note: this remains true, it should be far easier to automate a subway system than to create a fleet of driverless cars).

Despite the inherent geometric challenges of personal transit as a service, the system nevertheless demonstrated the value of guideways; and also the reasons why we don’t have more of them: local opposition and cost. One PRT booster:

To Kornhauser, the issue is less that the technology was inherently inadequate than that it was expensive and inconvenient. “You didn’t need that much intelligence in the vehicle to be able to do all this stuff,” he says. “The problem was that nobody really wanted to invest the money to build the exclusive guideway. That’s the short and the long of it.”

And Robertson on the local opposition to erecting concrete guideways all over the city:

Even the most time-tested (and desperately needed) public transit systems have trouble securing space and laying track; New York City’s history is littered with unbuilt subway lines that were killed by local protests and a lack of money. PRT guideways had some advantages over trains, like their near-silence, but they would still require cities to build miles of concrete chutes. And unlike a subway line extension, there would be no guarantee that people would accept the new system. Or, as one former transportation commissioner told NPR when asked about personal rapid transit last year: “The last thing you want to do is put up some track all over the place and have it just there.”

Also, unlike a more traditional elevated line (something I’ve defended here previously), the ideal of PRT means offering door to door transit, which in turn requires a guideway of some kind from door to door.

Don’t rule out elevated rail in cities

Toronto is looking to Honolulu for transit inspiration – looking to tap into the potential for elevated rapid transit to improve the city’s transit expansion plans. However, key city officials are extremely concerned about the impacts of elevated transit to the city. Skepticism is good, any may be required to ensure that elevated rail is successfully integrated into an urban environment, but it shouldn’t be an automatic disqualifier for the kinds of improvements that make rapid transit possible. From the Toronto Star:

Toronto chief planner Jennifer Keesmaat cites the shadow that a structure like the [elevated Gardiner expressway] casts on the street below. She also brandishes one of the chief arguments for building Toronto’s LRTs in the first place.

“From a land use planning perspective, if our objective in integrating higher order transit into our city is to create great places for walking, for commerce, living,… elevated infrastructure doesn’t work so well for any of those objectives,” she said.

It’s true that making elevated rail work in urban areas is a challenge, but it shouldn’t be so easily dismissed. Of particular concern is the willingness to equate the visual impact of the six-lane Gardiner Expressway with a potential two-track elevated rail structure. The other key concern is the equivocation of grade-separated transit with at-grade light rail.

Toronto seems full of transit terminology confusion these days. Embattled Mayor Rob Ford has been pushing for subways as the only kind of transit that matters (SUBWAYS SUBWAYS SUBWAYS!) regardless of context or cost. Meanwhile, the transit agency is looking to implement a ‘light rail’ project that features full grade separation and an exclusive right of way – in other words, a subway. Ford opposes the light rail plan in favor of an actual, tunneled line with fewer stations and higher cost. Much of the rhetoric seems focused on equating light rail with Toronto’s legacy mixed-traffic streetcar network.

However, just as Ford’s dogmatic insistence of subways at any cost is irresponsible, Keesmaat’s suggestion that at-grade LRT can accomplish the same transit outcomes as grade-separated LRT can is equally misleading. Remember the differences between Class/Category A, B, and C right of way (from Vukan Vuchic, summarized here by Jarrett Walker), paraphrased here:

  • Category C – on-street in mixed traffic: buses, streetcars, trams, all operating in the same space as other street users.
  • Category B – partially separated tracks/lanes: exclusive right of way for transit, but not separate from cross-traffic. Vuchic dubs this “Semirapid Transit.” often seen with busways or light rail.
  • Category A – right of way exclusive to transit, separated from all cross traffic: This is required for rapid transit. Examples include subways/metro systems and some grade-separated busways.
Transit system types by class of right-of-way.

Transit system types by class of right-of-way. X-axis is system performance (speed, capacity, and reliability), Y-axis is the investment required.

The distinction matters because the quality of the transit service is substantially different. Service in Class A right of way will be faster and more reliable than Class B, at-grade LRT. Part of the planning challenge is matching the right level of investment (and ROW category) to the goals for the system. However, even with the need to balance transit goals with those for urban design, planners like Keesmaat shouldn’t categorically dismiss the possibility of building Class A transit facilities.

Part of the confusion might be from the technology. A catenary-powered rail vehicle can operate in Class A, B, or C right of way, and fill the role of streetcar, light rail, or metro – all with little change in technology. Consider San Francisco, where Muni trains operate in all three categories – in mixed traffic, in exclusive lanes, and in a full subway. The virtue of light rail technology is flexibility, but that flexibility can also confuse discussions about the kind of transit system we’re talking about. The vehicle technology isn’t as important as the kind of right-of-way. Indeed, many of the streetcar systems that survived the rise of buses precisely because they operated in Class A and B rights-of-way.

Keesmaat certainly appreciates the difference between the kind of regional rapid transit you’ll see in Honolulu and at-grade LRT:

“The Honolulu transit corridor project is really about connecting the city with the county…. It’s about connecting two urban areas. That’s very different from the context we imagine along Eglinton where we would like to see a significant amount of intensification along the corridor,” said Keesmaat.

At the same time, the kind of transit she’s describing and the kind of land use intensity aren’t mutually exclusive at all – quite the opposite.

densitytable2withcap

Subways are nice, but require a high level of density/land use intensity. Payton Chung put it succinctly: “no subways for you, rowhouse neighborhoods.” Payton cites Erick Guerra and Robert Cervero’s research on the cost/benefit break points for land use density around transit lines. This table to the right shows the kind of density needed to make transit cost-effective at various per-mile costs.

The door swings both ways. Rowhouse densities might not justify subways, but they could justify the same Class A transit if it were built at elevated rail construction costs. Finding ways to lower the high US construction costs would be one thing, but given the systemic increase of US construction costs, using elevated transit would be a good way to extend Class A rights-of-way to areas with less density.

Instead of categorically dismissing elevated rail, work to better integrate it into the urban environment. Consider the potential for the mode to transform suburban areas ripe for redevelopment. Wide rights-of-way along suburban arterials are readily available for elevated rail; redevelopment can not only turn these places into walkable station areas, but also help integrate elevated rail infrastructure into the new built environment.

Keesmaat’s concerns about elevated rail in Toronto stem from the impact on the street:

“The Catch22 with elevating any kind of infrastructure – a really good example of this is the subway in Chicago – not only is it ugly, it creates really dark spaces,” she said.

It’s not just the shadow but the noise of elevated transit lines that can be problematic, said TTC CEO Andy Byford. If you build above the street you’ve also got to contend with getting people there, that means elevators or escalators.

First, it’s not clear what Byford is talking about: accessing subway stations also requires elevators and escalators. The nature of grade separated rights-of-way is that they are separated from the grade of the street.

Keesmaat’s concerns about replicating Chicago’s century-old Els are likely misplaced. No one is building that kind of structure anymore – and a quick survey of newer elevated rail shows slimmer, less intrusive structures. Reducing the visual impact and integrating the transit into the cityscape is the real challenge, but the price advantage and the benefits of Class A right-of-way cannot be ignored. It’s not a surprise that the Star paraphrases UBC professor Larry Frank: “On balance… elevated transit should probably be considered more often.”

What would change with driverless cars?

Robocar electronics - CC image from Steve Jurvetson

If we can agree that technology doesn’t change geometry, and therefore driverless cars won’t substantially change the fundamental capacity and spatial requirements of our current auto-based transportation systems, then what would they change?

Chris Bradford takes a stab at this question, taking note of Matt Ygleisas’s prediction of reduced demand for parking. Matt cites the idea of having a driverless car drop you off at a commuter rail station in the morning in order to make use of the higher capacity rail system to enter the city (thanks to the relevant geometries of rapid transit), while the car would then return to your house – eliminating the need for more car storage at the rail station. Chris takes that one step further, noting that with a tireless ‘driver,’ the needs for vehicle storage wouldn’t need to use a set space at all, but could be accomplished through cruising.

While both ideas would reduce the need for parking spaces, they would also increase the VMT for any given trip – either through cruising for parking or for increased deadhead trips, further clogging the streets. This might not be a problem in certain cases where congestion isn’t currently an issue, but it sure wouldn’t help in places where congestion is already a problem.  Bradford notes this:

In fact, this perfectly rational practice will probably be so harmful, so patently selfish, so despised that it will be necessary to outlaw it. Which means everyone will still have to find a spot for his car, driverless or not. Which means that, despite the title of this post, we might not see a robocar apocalypse after all, or a parking bubble, either (other than the existing bubble that local governments have created with underpriced street parking and mandatory parking minimums.)

Perhaps the most interesting application, then, isn’t the need to store a car for personal use (given the issues of storage raised above), but to allow that car to be used productively by someone else.  A driverless taxi, otherwise (hence my choice for my previous post’s image of Total Recall’s Johnny Cab – I don’t know if the new version of the film this summer will depict the Johnny Cab, if it does so at all).

You can already see the convergence of different car ownership models.  A taxi is owned by an operator, they provides rides for hire, charging you for the convenience of the trip in their car and for not having to drive yourself. Compare that to the current point-to-point carsharing model like Car2Go, and the only real difference is the driver.  Both charge based on time and/or distance traveled, both offer point to point trips in a vehicle you don’t own.

While the cost of these robocars would likely come down over time, they’d still be more expensive than regular ol’ human-driven cars, meaning that the trends towards collaborative consumption would continue, and the robocars would serve their best use as taxis.  The value of owning one yourself would be limited, unless you had a ton of disposable income.

As Matt Yglesias put it, “imagine a world of cheap, ubiquitous taxis.”  The net impact would be favorable to cities and those who live in them.  The limits of the automotive geometry and capacity wouldn’t fundamentally change, so this would still be a premium service over much higher capacity mass rapid transportation.  The benefits of owning a car would continue to decline in urban areas, as would the cost of the auto-based alternatives (like taxis).

The Need for Speed

A streetcar speeds by in Toronto. CC image from Matthew Burpee.

A streetcar speeds by in Toronto. CC image from Matthew Burpee.

Jarrett Walker has a wrap-up post on his debate with Patrick Condon on the need for speed in urban transit.   Condon is a professor of sustainability, not a transportation planner or engineer, and his view is that we need to improve the experience of sustainable transit and not enable the sprawling lifestyles of yesterday, no matter what mode we use to get to and fro.  Jarrett sums up Condon’s thesis in an earlier post:

Condon heads the Design Centre for Sustainability inside UBC’s Department of Architecture and Landscape Architecture, and is the author of the very useful book Design Charrettes for Sustainable Communities. In his 2008 paper “The Case for the Tram: Learning from Portland,” he explicitly states a radical idea that many urban planners are thinking about, but that not many of them say in public.  He suggests that the whole idea of moving large volumes of people relatively quickly across an urban region, as “rapid transit” systems do, is problematic or obsolete:

The question of operational speed conjures up a larger issue: who exactly are the intended beneficiaries of enhanced mobility? A high speed system is best if the main intention is to move riders quickly from one side of the region to the other.  Lower operational speeds are better if your intention is to best serve city districts with easy access within them and to support a long term objective to create more complete communities, less dependent on twice-daily cross-region trips.

It’s an interesting question, and it’s having a significant if not always visible impact on transport planning.  Darrin Nordahl’s 2009 book My Kind of Transit, reviewed here, also praises slow transit; he makes that case in the same way you’d advocate for “slow food,” by pointing to the richness of experience that comes only from slowing down.

The implication is clear, as Jarrett states in the title of his posts – “is speed obsolete?”  Jarrett’s counter-point, however, is that speed matters, and it matters a great deal:

So here’s my main point:

Rapid transit is a far more viable “augmenter” of pedestrian trips because its travel speeds, and thus the trip-lengths for which it’s suited, lie entirely outside the pedestrian’s range, whereas the streetcar overlaps the pedestrian range substantially.

The rapid transit and pedestrian modes play entirely complementary roles, while streetcar and pedestrian modes have partly overlapping roles — a less efficient arrangement.  You’ll walk further to a rapid transit station, but once you’re there you can move at a high speed that makes that extra walk worthwhile […]

Rapid transit’s speed also exceeds typical cycling speed, by a large enough factor that it makes sense to cycle to the station.  So rapid transit works with cycling to a degree that local stop transit, such as the Portland Streetcar, just doesn’t.

Obviously, the usefulness of rapid transit requires a longer trip length, so rapid transit should be considered only for relatively long corridors.  As several commenters have mentioned, the problem with Condon’s view may be in the corridors to which he’s applied it, including Vancouver’s Broadway corridor, where he’s presented it as an alternative to a SkyTrain extension.

Streetcars and rapid transit are different tools, each suited for different jobs.  I’d argue that some of the value in streetcars is precisely because they can fill in the gaps of a hub-and-spoke system like Metro, while the aforementioned Broadway corridor in Vancouver probably should be one of the spokes. The question is then one of how you use that tool.  One thing to remember about Portland’s streetcar is that the station spacing is very close, especially when you consider Portland’s short blocks. Small adjustments, such as wider station spacing and some signal priority treatments could greatly improve performance and reliability.

DC’s proposed streetcar system can take better advantages of the streetcar’s strengths as a mode.  Yonah Freemark’s excellent graphics on DC’s network show how streetcars can fill in some of the crosstown gaps that exist in the current Metro network. However, streetcars certainly are not and cannot be a substitute for Metro’s utility to the city and the region.  Yonah also chimes in on the subject over at The Next American City:

By advocating streetcars, Condon is implicitly arguing that people should stay in their neighborhoods for most of their trips; that they should find work, go shopping, and be entertained in their near surroundings. If people have to rely on slow transit, they simply won’t have the time to be making trips across the region. (Or, of course, they might switch to driving their private automobiles, which would defeat the point of the transit investment entirely.)Though this approach would likely produce better ecological outcomes (less energy consumption per person as a result of reduced transport mileage), it would exacerbate spatial inequalities. Because jobs (especially well-paid ones) tend to be concentrated in the favored quarter, poorer inhabitants living far away from that zone would be isolated from employment opportunities and thus be deprived of chances for income growth. Or they would face devastatingly long commutes.

Stepping outside of the fiscally constrained world, the obvious answer is that both rapid and circulator systems serve different and complimentary needs.  The economic implications (for a city’s economy, rather than just real estate development) are the really interesting – Walker’s commenter ‘micasa’ highlights Jane Jacobs and the very nature of cities:

What does the venerable Jane Jacobs have to say about the notion of a “city of neighbourhoods”?

“Whatever city neighborhoods may be, or may not be, and whatever usefulness they may have, or may be coaxed into having, their qualities cannot work at cross-purposes to thoroughgoing city mobility and fluidity of use, without economically weakening the city of which they are a part. The lack of either economic or social self-containment is natural and necessary to city neighborhoods – simply because they are parts of cities.”

Jacobs is describing what does, and always has, made cities “tick”.  To be against intra-urban mobility is to be against the very proposition of the city.  I don’t think we can afford to let the threat of climate change, peak oil, or whatever, destroy that. We may need radically different, more sustainable cities in the future if we are going to survive, but rest assured, we will still need cities. Not agglomerations of inward focused neighbourhoods, but cities.

I’m not suggesting that the debate over transit technologies in this particular case ought to be closed. But I am suggesting that Condon’s particular argument for surface rail – that it encourages local living in a neighbourhood setting – is fundamentally anti-urban.  A better argument, and one that actually addresses the urban mobility issue, is that perhaps surface rail is a cheaper solution that can be designed “fast enough” to allow those neighbourhoods on the West Side (including UBC) to cohere with the rest of the region without the necessity of cars (and vice-versa). But that’s not the argument as presented.

Is speed obsolete?  I’d say no.  To micasa’s last point, surface rail can indeed be designed to be ‘fast enough’ to address urban mobility, particularly when paired with an existing rapid transit system (such as DC’s Metro).