Bus Rapid Transit

Portland’s Division Transit Project: A New Kind of “Rapid” Urban Bus

For the past few years, planners at the transit agency TriMet and MPO Metro in Portland have been carefully shepherding the development of a new sort of transit project for the city.  It’s turning into a new sort of transit project, period — one that doesn’t fit in the usual categories and that we will need a new word for.

The Powell-Division Transit and Development Project extends from downtown across Portland’s dense inner east side and then onward into “inner ring suburb” fabric of East Portland — now generally the lowest-income part of the region– ending at the edge city of Gresham.  It was initially conceived as a Bus Rapid Transit (BRT) line, though one without much exclusive lane.  It would be a new east-west rapid element in Portland’s high-frequency grid, and also serves a community college and several commercial districts.

(Full disclosure: JWA assisted with a single workshop on this project back in 2015, but we haven’t been involved in over a year.).

Below is a map of how the project had evolved by 2015, with several routing choices still undetermined.  From downtown it was to cross the new Tilikum bridge and follow Powell Blvd. for a while  Ironically, as inner eastside Portland began to be rethought for pedestrians and bicycles, decades ago, Powell was always the street that would “still be for cars.”   To find most of the area’s gas stations and drive-through fast food, head for Powell.  As a result, it’s the fastest and widest of the streets remaining, but correspondingly the least pleasant for pedestrians.

Half a mile north is Division Street.  For the first few miles out of downtown, Division is a two lane mainstreet, and it’s exploded with development.  It’s on the way to being built almost continuously at three stories.  Further out, Division is one of the busier commercial streets of disadvantaged East Portland, though still very suburban in style as everything out there is.  (For an amusing mayoral comment on that segment, see here.)

Because dense, road-dieted Division is very slow close to the city but wide and busy further out, the project began out with the idea of using Powell close-in and then transitioning to Division further out, as Division got wider, though of course this missed the densest part of Division, which is closest-in.

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However, very little of the corridor would be separated from traffic. While this project was never conceived as rail-replicating, it was based on the premise that a limited-stop service using higher-capacity vehicles, aided by careful signal and queue jump interventions, could effect a meaningful travel time savings along the corridor, compared to trips made today on TriMet’s frequent 4-Division.  That line runs the entire length of Division and is one of the agency’s most productive lines, but it struggles with speed and reliability.

As it turned out, though, the travel time analyses showed that from outer Division to downtown, the circuitous routing via Powell cancelled out any travel time savings from faster operations or more widely spaced stops.

As a result, planners looked at a new approach, one that would seek to improve travel times by using inner Division, which had previously been ruled out. Inner Division is a tightly constrained, 2-lane roadway through one of the most spectacularly densifying corridors in Portland, and one that is rapidly becoming a prime regional dining and entertainment destination. This development has led to predictable local handwringing about parking and travel options. Here’s what that alternative looks like:

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Proposed Division station locations


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Current 4-Division eastbound stops

The new plan is basically just stop consolidation with some aesthetic and fare collection/boarding improvements. But the stop consolidation would be dramatic.  Note that one numbered avenue in Portland represents about 300 feet of distance, so the new spacing opens up gaps of up to 2400 feet.  If you’re at 30th, for example, you’d be almost 1/4 mile from the nearest stop.

Such a plan would be controversial but quite also historic.  It’s a very wide spacing for the sole service on a street.  On the other hand, the wide spacing occurs on a street that is very, very walkable — one of the city’s most successful “mainstreets” in fact.  And it’s basically the only way to optimize both speed and frequency on a two-lane mainstreet like inner Division.

At this point, it would be strange to call this project “BRT” (Bus Rapid Transit); even the project webpage refers to this alternative as “Division rapid bus”.

Disappointing as this will be to those who think BRT should emulate rail, it has one huge advantage over light rail.  In Portland, surface light rail tends to get built where there’s room instead of where existing neighborhoods are, so it routinely ends up in ravines next to freeways, a long walk from anything.  This Division project now looks like the answer to a more interesting question:  What is the fastest, most reliable, most attractive service that can penetrate our densest neighborhoods, bringing great transit to the heart of where it’s most needed?

This is such a good question that we shouldn’t let arguments about the definition of “BRT” distract from it.  Because it’s not a question about technology.  It’s a question about people.

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Line 72 stopping pattern (Powell to Division, approx. 0.5 mi)

Upgrading the 4-Division to a rapid bus line (without underlying local service, which is impossible due to the constrained roadway) should present a real improvement in quality of service (in terms of capacity using the larger vehicles, and in a 20-25% travel time savings), while at the same time being easier to implement and less disruptive to existing travel patterns.

It also provides a template for TriMet to consider stop consolidation and frequent rapid service on other corridors like the aforementioned Line 72. Rather than seeing this as a failure to design a rapid transit project, perhaps we can celebrate a process that has steered away from a path that would have resulted in a disappointing outcome, towards a more limited, more economical, but still meaningful improvement for riders.

Does the History of a Technology Matter?


Mater Hill busway station, Brisbane

Ben Ross has a nice long read in Dissent about the history of Bus Rapid Transit, noting all the ways it’s succeeded, failed, and been co-opted by various non-transit agendas.  He’s especially interested in the way various petroleum-and-asphalt interest groups have supported BRT as an alternative to rail for reasons that probably don’t have much to do with their love of great public transit.  All this is worth reading and knowing about.

But what, exactly, should we do with this history?  Practically everything that breaks through into the public discourse has private public relations money behind it, and that money always has different goals than you and your city do.  That’s why you should always lean into the wind when reading tech media.  But just as it’s wrong to fall for everything you read in corporate press releases, it’s also wrong to reflexively fall against them.  (Cynicism, remember, is consent.)

Galileo paid the bills, in part, by helping the military aim cannonballs correctly.  Does that mean pacifists should resist his insight that Jupiter has moons?

So while I loved Ross’s tour of the history, I reject his dismissive conclusion:

Buses will always be an essential part of public transit. Upgrading them serves urbanism, the environment, and social equity. But a better bus is not a train, and bus rapid transit promoters lead astray when they pretend otherwise. At its worst, BRT can be a Trojan horse for highway building. Even at its best, it is a technocratic solution to a fundamentally political problem.

The term technocratic is really loaded here.  Given the new “revolt against experts” trend in our politics, we urgently need to recognize  hard-earned expertise and to distinguish it from elite selfishness, but technocrat is a slur designed to confuse the two.


RBWH busway station, Brisbane

There are some great bus rapid transit systems out there, and not just in the developing world.  The mixed motives that underlie BRT advocacy don’t tell us anything about where BRT makes sense, any more than the mixed motives behind rail advocacy do.

A light reading of history can help you recognize the prejudices that may lay behind advocacy on all sides.  But then you have to set that aside, and think for yourself.


the explosive global growth of bus rapid transit (BRT)

recent study from ITDP  surveys the growth of BRT around the world over the past decade.  

BRT Infographic


Note that IDTP thinks of BRT as something that matches the performance of rail using buses.   ITDP's BRT standard excludes many of the projects that the US Federal Transit Administration calls BRT, which amount to premium buses in mixed traffic with minimal speed and reliability features.*  

China has created the largest quantity of true BRT systems, but of course in per capita terms it's Latin America that is building true BRT most intensively.  Fast-developing middle-wealth countries like China, India, Mexico, and Brazil are the sweet spot for BRT because (a) car ownership is still moderate, (b) government power tends to be consolidated enough that decision making is easy, (c) there is simply not enough money to build massive rail transit systems, at least not quickly and at the necessary scale.  

This news is also interesting in light of the forthcoming Rio de Janeiro conference on climate change, and the rumours that China may be ready to commit to reducing emissions, putting pressure on India to do the same.  Latin America, where many countries of similar wealth already have relatively strong climate change policies, is the perfect site for this conversation.

The other interesting stat is how rapidly the BRT revolution has moved.  Of all the true BRT in the world, 75%  was built in the last decade, mostly in middle-income countries, and the pace shows no signs of abating.

Fortunately, those middle income countries amount to a big share of the world, which could mean a real impact on global transportation impacts over time.


* (I tend to agree with ITDP's concern that the overly weak use of the term BRT is making it hard to talk about the original point of the BRT idea, which was to mimic what rail rapid transit does in terms of speed, frequency, and reliability.  This meaning is inherent in the "R" in BRT, which means "rapid".)

silicon valley: bus rapid transit that’s faster than driving?

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El Camino Real BRT Alignment


Silicon Valley is easily viewed as a  car-oriented place, where tech giants rule from business parks that are so transit-unfriendly that they have had to run their own bus systems to bring employees from afar.  But one interesting transit project is moving forward: the El Camino BRT, a proposed  rapid transit line connecting Palo Alto and central San Jose. 

El Camino Real ("the Royal Road") is a path defined by Spanish missionaries as they spread north through California. It lies close to the old railroad line now used by Caltrain, and the two facilities combined  determined the locations of the pre-war transit-oriented downtowns that still form the most walkable nodes in the area.  

Today El Camino is the spinal arterial of the San Francisco peninsula, passing through or near most of the downtowns.   This spine continues across Silicon Valley, through Palo Alto, Mountain View, Sunnyvale, Santa Clara and finally downtown San Jose.   (The BRT will not extend the full length of the peninsula, because it is a Santa Clara County project and the county ends at Palo Alto.  However, successful projects do get extended sometimes.)   In Silicon Valley, too, the corridor is far enough from Caltrain that they are not competing.  Caltrain will always be faster but probably less frequent than the BRT, optimized as it is for much longer trips including to San Francisco.

In land use terms, the project corridor is ideal territory for transit – lots of employment and commercial destinations, with strong anchoring institutions at each end.   But while the path is historic, the modern street was designed with a singular focus on auto travel time, as a six-lane divided boulevard. Auto and transit travel times continue to increase substantially as more people come to live and work in the corridor, and even more population and employment growth is forecast for the coming decades.  

Santa Clara VTA and the FTA released the Draft Environmental Impact Report for this project last week, detailing multiple alternatives relating to the extent of dedicated lanes and street configurations. The purpose and need statement tidily summarizes the rationale for this investment:

El Camino Real is an important arterial in Santa Clara County and on the San Francisco Peninsula. However, El Camino Real is predominantly auto-oriented, and streetscape amenities are limited. There are widespread concerns regarding congestion, appearance, and safety, and a general public perception exists that the corridor is not well planned. Exacerbating current conditions, Santa Clara County is expected to experience substantial growth in the next 30 years from 2010 to 2040. If no improvements are implemented, heavy demand will potentially be placed on the existing transportation infrastructure, which is planned to increase by only 5 to 6 percent. 

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This striking graph (which I couldn't locate in the report itself, but which is reproduced over at the TransForum blog), compares transit travel time among the four alternatives:

In the A4c alternative (the alternative with the greatest extent of exclusive lanes), a trip during the peak through the corridor would actually be faster on transit than driving, and dramatically faster than the same trip today.

The various alternatives' alignments are compared below:

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As usual with arterial BRT in the US, there will be some mixed-traffic segments, and the line will only be as realiable as its least reliable point.  Note that the alternatives seem to envision different responses to city limits, as though anticipating that as you get further west (which means wealthier, but also closer to big destinations like Palo Alto and Stanford University), support for exclusive lanes will decline.  It will be interesting to see if this is true, in a very educated polity, when the benefits are understood.  

quote of the week: “rail is only part of the equation”


Trains would be just one layer of a comprehensive, multi-modal network that greatly enhances both neighborhood and regional accessibility for people all across the [Los Angeles] region. …

A singular focus on rail would divide the region into two: neighborhoods with rail and neighborhoods without. Such a future would perpetuate income inequality as housing costs rise near stations and station areas would be choked with traffic congestion. …

Getting our existing buses out of traffic is the quickest, most cost-effective means to bring high-quality transit to the greatest number of Angelenos.

Juan Matute, UCLA Institute of Transportation Studies
from a discussion called "Trains are Not the Silver Bullet"
 at ZocaloPublicSquare

This is from a collection of commentary about the the role of rail in the larger context of transit investment strategies.  Read the whole thing!






quote of the week: the neglected american bus

In the six cases examined, we conducted off the record interviews with public officials, general managers, and thought leaders in each region. One of the consistent themes that emerged was that the bus systems and bus passengers were an afterthought. In every region – Chicago, New York, Boston, Minneapolis/St. Paul, Dallas/Ft. Worth, and the Bay Area – rail was the primary focus of virtually everyone we interviewed. We also found that maps of the regional transit networks tellingly either included a jumbled mess of bus routes behind a clean rail network, or ignored bus altogether.

It is likely this bias toward rail has very little to do with governance. But it does have a negative impact on transit delivery, particularly from a customer point of view. The vast majority of transit riders in the United States are on buses, so it would make sense to devote more resources and attention to them compared to rail riders, rather than less. Also, improvements to the bus network are likely to be less expensive than new rail expansions, and would be likely to yield substantially more net benefit per dollar. Yet while every region we visited had a new rail expansion either in planning or under construction, outside of New York none of the regions had any plans for regional bus networks, reorganization of existing bus systems, or major expansions of bus rapid transit (BRT).

Joshua Schank, President CEO,
Eno Center for Transportation
"The Case of the Neglected Bus"

I've certainly noticed, in my own work, that the aggressive, agency-wide commitment to building a complete access-maximizing transit system is stronger in cities that don't have much rail, or where rail is in early stages of development, as in Houston.  Key tools for total network legibility, such as Frequent Network branding, also seem to be spreading much more effectively in the midsized transit authorities than in the gigantic ones.

A while back I had a brief chat with a major airline CEO at an event.  He asked me: "So what's the future of transit.  It's rail, isn't it?"  I wanted to say: "So what's the future of aviation?  It's all intercontinental jumbo jets, isn't it?  

Or is it about people feeling free to go places?  In that case, the future of aviation is a network, where many types of vehicle have an essential role.  

Does transit infrastructure cause ridership?

Does building a new transit line trigger ridership?  Does it even make sense to talk about the ridership of a piece of transit infrastructure?  

If you say yes, you're expressing an infrastructurist world-view that is common in transit investment discussions.  The right answer to the above questions, of course, is "No, but:

  • Infrastructure permits the operation of some kind of useful transit service, which consists of vehicles running with a certain speed, frequency, reliabilty, civility and a few other variables.
  • That service triggers ridership."

To the infrastructurist, this little term — "service" — is a mere pebble in a great torrent of causation that flows from infrastructure to ridership.  By contrast, service planners, and most transit riders that I've ever met, insist that service is the whole point of the infrastructure.

If you read the literature of infrastructure analysis, you  encounter the infrastructurist world view all the time, mostly in ways that's unconscious on the authors' part but still a source of confusion.  This afternoon I was browsing TCRP 167, "Making Effective Fixed-Guideway Transit Investments: Indicators of Success", which includes some really useful explorations of land use factors affecting the success of transit lines.  But when they talked about infrastructure features as causes of ridership, the report routinely delivered weirdness like this:

The percentage of the project’s alignment that is at grade proved to be a negative indicator of project-level ridership. At-grade projects may be more prevalent in places that are lower in density, while transit is more likely to be grade-separated in places with higher density or land value. Thus, this indicator may be reflective of density. It may also be true that at-grade systems are slower than grade-separated systems. At-grade status may reflect a bundle of operational characteristics such as speed, frequency, and reliability, although the analysis did not find that these factors individually had a statistically significant effect on ridership.  [TCRP 167, 1-17]

This careful talk about how a correlation "may" reflect density or "operational features" sounds vague and speculative when it's actually very easy to establish.  There is no shortage of evidence that:

  • High density reliably triggers ridership.
  • Areas of high density are less likely to have available surface rights of way.
  • Therefore, highest ridership segments tend to be grade-separated.

So this is a case where "A correlates with B" does not mean "A causes B" or "B causes A".  It means "A and B are both results of common cause C".  It's important to know that, because it means you won't get B simply by doing A, which is the way that claims of correlation are usually misunderstood by the media and general public.

Later in the paragraph, the authors again describe the obvious as a mystery:

At grade status may reflect a bundle of operational characteristics such as speed, frequency, and reliability …  

Yes, it certainly may, but rather than lumping all the at-grade rail projects together, they could have observed whether each one actually does.  

… although the analysis did not find that these factors [speed, frequency, and reliability] individually had a statistically significant effect on ridership

While this dataset of new infrastructure projects is too small and noisy to capture the relationship of speed, frequency, and reliability to ridership, the vastly larger dataset of the experience of  transit service knows these factors to be overwhelming.  What's more, we can describe the mechanism of the relationship, instead of just observing correlations:  Speed, frequency, and reliability are the main measures of whether you reach your destination on time.  Given this, the burden of proof should certainly be on those who suggest that ridership is possibly unrelated to whether a service is useful for that purpose.

Note the word choice:  To the infrastructurist, speed, frequency and reliability are dismissed as operational, whereas I would call them fundamental.   To the transit customer who wants to get where she's going, these "operational" variables are the ones that determine whether, or when, she'll get there.  It doesn't matter whether the line is at-grade or underground; it matters whether the service achieves a certain speed and reliability, and those design features are one small element in what determines that.  

I deliberately chose a TCRP example because the authors of specific passages are not identified, and I have no interest in picking on any particular author.  Rather, my point is that infrastructurism so pervasive; I hear it all the time in discussions of transit projects.  

I wonder, also, if infrastructurism is a motorist's error: In the world of roads, the infrastructure really is the cause of most of the outcomes; if you come from that world it's easy to miss how profoundly different transit is in this respect, and how different the mode of analysis must be to address transit fairly.

Whenever you hear someone talk about the ridership of a piece of infrastructure, remember: Transit infrastructure can't get people to their destinations.  Only transit service can.  So study the service, not just the infrastructure!




brisbane: a city transformed by a bus link

Next time someone tells you that transit has to be rail in order to affect real estate demand, send them this paper [paywalled] by Elin Charles-Edwards, Martin Bell and Jonathan Corcoran –  a dramatic example of bus infrastructure profoundly transforming residential demand.

Our scene is the main campus of University of Queensland, which is located on a peninsula formed by a loop of the Brisbane River.  It's in the southwest corner of this image.  The area labeled "Brisbane" is the highrise downtown.  Most everything in between — which is mostly on the south side of the river — is dense, redevelopable inner city fabric.  

Bris cbd

If you look closely you can see a single faint bridge connecting the University across the river.  This is the Eleanor Schonell Bridge, which opened in 2006, and which is solely for pedestrians, cyclists, and buses.  No private cars.  It's one of the developed world's most effective of examples of a transit path that is vastly straighter than the motorist's options.

Prior to the opening of the bridge, University of Queensland had a problem much like that of Vancouver's University of British Columbia.  Its peninsula setting helped it feel remote and serene (the rarefied air of academe and all that) but it was also brutally hard to get to, especially from places where students and lower-paid staff could afford to live.  While there are some affordable areas west of the campus, most of the immediate campus area is far too affluent and low-density to house the university's students or the bulk of its workforce.  So commutes to the campus were long and difficult.  

Apart from the geography of income, the issue here was classic chokepoint geography, and that was the key to the transit opportunity.  Brisbane's looping river, and its extreme shortage of bridges outside of downtown, slices the city into a series of hard-to-access peninsulas.  Motorists are used to driving way out of direction to reach their destinations, and until recently, buses had to do the same thing.  The only transit that could do what cars couldn't was the river ferry system, CityCat, and while this system is immensely successful, it is still a small share of the travel market because (a) so much of the population is not on the river and (b) the river is a  circuitous travel path as well.  

Charles-Edwards et al show how the bridge created an explosive expansion of access (where can I get to, soon?) for the campus by walking, cycling, and bus service.  Walking:

Uq walkshed

And by bus (focus on the triangle in the centre of the image, which is the campus):

Uq busshed

It's worth noticing why this bus bridge is so effective:  It plugs right into the Brisbane Busway network, which looks like this.  ("UQ Lakes" is the campus stop.) 


Direct buses from campus run along most of these paths, and connect to many other frequent services covering the area south of the river, including a couple of useful frequent rail lines extending southeast from downtown.   This is the biggest and highest-quality busway system in the developed world, in terms of the degree of protection from private car traffic along complete travel paths, including a tunnel under downtown.  So the access opened up by this bridge was extraordinary.  The busway is so fast and reliable that even commutes from northern Brisbane — on the same side of the river as the campus — were speeded up by the new bridge because they could remain in busway for the entire journey.

The effect on the location of students and staff, from 2003 until 2012 (six years after the bridge opened) looks like this.

Uq relocations

The colour choices are unfortunate, so pay attention to the legend and focus on "St Lucia" (the campus) and the inner city areas just across the river from it. Remember, too, that this is a map of percentage change, so don't be distracted by big colors far away from the action, which represent noise (percentage changes on a tiny base). You can see that students and staff have shifted in big numbers to the inner city across the river from the campus, but also to southern and eastern suburbs each of the river, which are more affordable and still easily reached by buses from the campus.  In the author's careful words, the bridge caused "a significant redistribution of staff and students across the metropolitan area."  It also had the likely effect of reducing overall commute times by enabling people to live much closer to the campus, though the authors don't mention that.  

Because the project gave buses so much of an advantage in accessing the campus, the mode share shifted dramatically, enabling the campus itself to grow without choking on cars:

 Between 2002 and 2011, the population accessing the campus increased by 23 per cent, … all of which were absorbed by [non-car modes on] the bridge. There was an accompanying shift in the modal mix of trips away from cars to public transport. This was most marked among students, for whom less than one-quarter of trips were by car in 2011, down from two-fifths in 2002. Bus patronage increased among students from around a quarter of trips to more than half. Staff car usage declined from 70 per cent in 2002 to just over half in 2011, with buses, cycling and walking all increasing in popularity.

Eleanor Schonell Bridge is a powerful example of infrastructure that transforms a city's living patterns by transforming the isochrones of access.  We can all think of trains and ferries that do this, but it's rare that buses are allowed to succeed in the same way.   Once again, Brisbane has shown that it's not the transit technology that matters to people's location choices.  It's where you can get to easily.

guest post: vehicle automation and the future of transit

Antonio Loro is an urban planner with a particular interest in transportation innovations. In research conducted for TransLink and Metrolinx, he investigated the potential impacts of vehicle automation technologies. The views expressed in this article are those of the author and do not necessarily represent the views of, and should not be attributed to, TransLink or Metrolinx.

AnthonyLoroVehicle automation is increasingly showing up on the radar of urban planning and transportation planning professionals. Technologies are developing rapidly, and some news stories report that fully self-driving cars are just a few years away. It’s tempting to envision automation ushering in a bold new era in urban transportation, where driverless cars whisk passengers between destinations safely and conveniently, use roads with great efficiency, and make public transit as we know it obsolete.

However, a closer look at vehicle automation reveals a more nuanced picture of the future. Automation capable of replacing human drivers in any situation may be many years away from the market. The traffic flow improvements enabled by automation will be limited in several ways. Buses and other forms of public transit will still be needed to efficiently move large numbers of travelers around cities. And various forms of automation in buses could enable major improvements in service.

The last two points have come up on this blog before (here, here and here), but since there are a variety of opinions on the implications of automation for transit, it’s useful to dig a bit deeper into these issues and take a critical look at when various forms of automation will arrive, how automation will affect traffic flow, and how it will affect travel behaviour. This post will delve into those questions to shed a bit more light on what automation means for the future of public transit.

According to some, vehicles that can drive themselves anywhere, anytime, without any human intervention – described as “Level 4” vehicles by the National Highway Traffic Safety Administration (NHTSA) – are just around the corner. In 2012, Google co-founder Sergey Brin said of their famous self-driving car: “you can count on one hand the number of years until ordinary people can experience this.” Many others have made bullish predictions. For example, the market research firm ABI Research foresees Level 4 cars on the roads by around 2020, and panelists at the Society of Automotive Engineers (SAE) 2013 World Congress predicted arrival between 2020 and 2025.

On the other hand, some point to a number of challenges that suggest Level 4 will emerge further down the road, perhaps not for several decades. Steven Shladover of the California Partners for Advanced Transportation Technology, a leading expert on vehicle automation, argues that Level 4 will be much more technically difficult to achieve than many optimists acknowledge (see Vol. 7, No. 3 here). According to Shladover, huge advances in technology would be needed to progress to systems capable of driving safely in the vast range of complex and unpredictable situations that arise on roads. In addition, such systems would have to be far more reliable than products like laptops or mobile phones, and extensive – and expensive – testing will be needed to prove reliability. While Google’s vehicles have driven long distances in testing – over 500,000 miles as of late 2013 – and have not caused any crashes while in automated mode, Shladover points out that this proves very little because their vehicles are monitored by drivers who take over when risky or challenging situations arise.

Legal and liability issues could also delay the emergence of Level 4 vehicles. A few American jurisdictions now explicitly allow automated vehicles on public roads for testing, and Bryant Walker Smith, a leading authority on the legal dimensions of vehicle automation, has found that automated vehicles are “probably” legal in the US; however, he also cautions that their adoption may be slowed by current laws. Laws will have to be clarified before Level 4 vehicles hit the mass market in the US and in other countries. Liability for crashes could also be a thorny question. If a human isn’t driving, presumably blame would shift to the manufacturer, or perhaps a supplier of system components, or a computer programmer. Resolving these issues could stall the emergence of automation.

While there is dispute as to when Level 4 vehicles will be on the road, most in the field agree that more limited forms of automation are coming soon. Some are already here. For example, Mercedes S-Class vehicles can simultaneously control speed and steering when road and traffic conditions allow, though the driver must continuously monitor the road. This is just shy of “Level 2” automation, since Mercedes’ system also requires the driver to keep their hands on the wheel. Numerous other vehicle manufacturers are developing advanced technologies that promise to take over driving duties, at least some of the time, on some roads. As technologies advance, “Level 3” vehicles could be on the market by 2020 to 2025, according to most experts. These vehicles would allow drivers to forget about monitoring the road and instead read or watch a movie, with the caveat that when the automated system is out of its depth, it would ask the driver to take over. (The takeover time is a matter of debate – anywhere from several seconds to several minutes has been suggested.)

Automation could be a boon for safety – or it could create new problems. On the plus side, it appears that crash avoidance systems already on the market may be effective. Of course, as machines take over more of the responsibility of driving, safety will only improve if the machines are in fact less fallible than humans. This might seem an easy task, considering the foibles of humans, but it’s worth remembering that some automation experts believe otherwise. And where driving is shared between human and machine, the safety impacts are especially open to question. A driver in a Level 2 vehicle might fail to continuously monitor the road, or a driver in a Level 3 vehicle could be engrossed in their movie and fail to take over control quickly enough when requested. In either case, automation could actually decrease safety.

After safety, one of the biggest selling points of vehicle automation is its potential for improving traffic flow, especially through increased road capacity. With their slow reaction times, human drivers can’t safely follow other vehicles closely, so even at maximum capacity, around 90 percent of the length of a freeway lane is empty. If machines could react quickly enough, road capacity would increase enormously. Some studies appear to suggest huge increases are in fact possible – for example, one study estimates that capacity would almost quadruple, and another finds quintupled capacity. However, their calculations consider endless streams of densely-packed vehicles. More realistic estimates assume that several vehicles, say four to twenty, would follow each other in tightly packed groups or “platoons”, with each group separated from the next by a large gap. These interplatoon gaps would provide safety and allow vehicles to change lanes and enter and exit the freeway. Studies that account for these gaps estimate that automation would increase capacity in the range of 50 to 100 percent (for examples, see here and here).

While the more realistic estimates of capacity increases are still very impressive, there are a number of caveats. First, short headways are possible only when automated vehicles are equipped with V2V, or vehicle-to-vehicle communication. Vehicles that rely completely on on-board sensors – such as the Google self-driving car, in its current form – cannot react quickly enough to the movements of other vehicles, so they would enable relatively small capacity increases. A second caveat: large capacity increases would come only when automated cars dominate the road. Studies have found that when fewer than 30 to 40 percent of vehicles on the road are capable of platooning, there would be little effect on capacity, and large increases would come only after the proportion of equipped vehicles exceeds 60 to 85 percent (e.g., see here). This is important, since new vehicle technologies will take some time to become commonplace. Imagine that as soon as automated vehicles hit the market, every new vehicle purchased is automated: it would then take two decades for automated vehicles to account for around 90 percent of vehicles on the road. If the rate of adoption is more realistic, but still rapid, it would take three decades or more before automated vehicles make possible large road capacity increases. A third major caveat: platooning is only feasible on freeways. Changing lanes, stopping at red lights, making left turns, parallel parking, stopping for pedestrians – such manoeuvres would make platooning impractical on city streets.

For city streets, however, there is the prospect of using automation to improve flows at intersections by coordinating vehicle movements. A good example is the “reservation-based” intersection, where there are no stop lights or stop signs – instead, cars equipped with V2I (vehicle-to-infrastructure communications) technology “call ahead” to a roadside computer that orchestrates the movements of vehicles and assigns time and space slots for vehicles to cross the intersection. Simulations show such an intersection could move almost as much vehicle traffic as an overpass – but so far, simulations haven’t included pedestrians and cyclists. Accommodating these road users in a reservation-based intersection would require signals with sufficiently long cycles, so capacity increases would be limited.

Vehicle automation would also bring a very direct impact: reduced or eliminated labour in driving. Time spent traveling in Level 2 vehicles could be less stressful, and could become more productive and enjoyable in Level 3 and especially in Level 4 vehicles. Profound changes in travel behaviour would result. As people increasingly let their robot chauffeurs deal with road congestion and other hassles of driving, travel by motor vehicle would become more attractive. Trips would tend to be longer and more frequent and travel at peak times would increase. Trip routes would also tend to make greater use of freeways with Level 2 and 3 vehicles, since it is primarily on these roads that the vehicles will be able to operate in automated mode.

These induced demand effects would tend to increase road congestion. Freeways would be the exception – if platooning-capable technology becomes widespread, freeway capacity would increase and congestion would drop. That is, until the surplus capacity is taken up by the “triple convergence” of mode shifts, route changes, and change of time of day of travel. However, the increase in freeway traffic would be constrained by capacity limitations on the rest of the road network – as freeway travel increases, new bottlenecks would form on streets near freeway entrances and exits, where automation does not boost capacity, thus restricting the volume of traffic that can access the freeway.

The upshot of the above observations on the capacity effects of automation is that even when the potential freeway capacity increases enabled by platooning are fully realized, automated cars would nevertheless be able to carry far fewer people than bus or rail on a given right-of-way. And, as mentioned, capacities on streets will be largely unaffected. Because the capacity improvements made possible by automation would be limited, we will still need buses and trains when space is in short supply and we need to transport large numbers of people. Larger vehicles will still fit a lot more people into a given length and width of right-of-way than platoons of small vehicles will be able to carry. As Jarrett would say, it’s a simple fact of geometry.

So, vehicle automation will not render large transit vehicles obsolete. On the contrary, it could enable significant improvements in bus service and increases in ridership. Automated steering enables bus operation at speed in narrow busways, which reduces infrastructure and land costs. It also enables precise docking at passenger platforms, which improves passenger accessibility and reduces dwell times. Automated control of speed enables bus platooning, allowing buses to effectively act like trains. Automation can be taken further yet: a driver in a lead bus can lead a platoon of driverless buses, thus providing high capacity with low labour costs. Similarly, individual buses or platoons can operate driverlessly, thus enabling increased frequency with low labour costs. “Dual mode” operation is also possible: imagine a busway where chains of buses leave the city running like a train until they separate at a suburban station, where drivers board and take them onward onto various local routings.

Some of these forms of automation have already been implemented in BRT systems. For example, a system in Las Vegas employed optical sensors to enable precise docking at passenger platforms, BRT buses in Eugene, Oregon used magnetic guidance to facilitate precision docking and lane-keeping in a pilot project, and systems in Paris and Rouen, France, and in Eindhoven, the Netherlands, use various types of guidance systems. While bus platooning and driverless operation have not been deployed so far, these applications could be achieved given sufficient technological advances – or by using a low-tech shortcut. The simple solution is to keep other vehicles or humans out of the way of the automated bus. If buses operate on busways with adequate protection, platooning and driverless operation is possible with existing technology. (Similarly, current driverless train systems are able to operate driverlessly, even with decades-old technology, by virtue of the well-protected guideways they run on.) Developing a vehicle capable of driving itself in the simplified environment of a protected busway is a considerably easier task than developing a vehicle that can drive itself on any road, anytime.

With the arrival of Level 4 automation, driverless buses could operate on the general road network. This would make it possible to operate smaller buses at higher frequencies, since labour costs would no longer constrain frequency. If you shrink driverless buses small enough – and provide demand-responsive service for individual travelers – you end up with driverless taxis. This points to the possibility that public transit service may be more efficiently provided by driverless taxis (or driverless share taxis) in low-density areas, thereby replacing the most unproductive bus services and improving transit productivity overall. (Of course, while automation could boost productivity, even driverless demand-responsive service would still have low productivity where densities are low.)

While it’s a seductive story that driverless cars will transport us to a realm of much improved safety, convenience, and efficient road use – and where public transit has dwindled away – the future is likely to be more complicated. Advanced automation is indeed coming soon, though we might not see Level 4 technologies for a while. Automation could improve safety, though it could also generate new problems. It could also improve road capacity, but the improvements would be limited in several ways. All this suggests that we needn’t worry about (or celebrate) how vehicle automation will make public transit obsolete. Instead, let’s focus on how to use automation to the advantage of public transit.