Basics

Basics: Expertise vs. Activism

The planning professions work in a grey zone between expertise and activism, and managing these competing impulses is one of our hardest tasks.

As a transit planning consultant, I don’t worry much about being perceived as an advocate of transit in general.  Experts in any field are expected to believe in its importance.  But I do try to keep a little distance between my knowledge about transit and the impulse to say “You should do this.”  A good consultant must know how to marry their own knowledge to their client’s values, which may lead them to make different recommendations than they would do as a citizen, expressing their own values.

Often, I use this blog and its comments to refine my own thinking about transit in the abstract.  This is part of how I cultivate my own expertise, but it is easy to mistake what I say for activism.  When I say, for example, that some of the widespread claims about the superiority of rail over buses are cultural feedback effects, I’m not thinking like an activist or advocate; I’m thinking theoretically, like a philosopher.  To me, this is a crucial skill for a consultant who’s going to have to marry his client’s values with his own expertise.

Philosophical or scientific training attunes you to the difference between prescription (telling people what they should do) and description (describing reality as it appears to be).  In their purest form, prescription is the job of ethics, while description the job of science and metaphysics.  A great deal of human speech, especially political speech, is a mixture of description and prescription, often one pretending to be the other.

In the planning world, prescription is the job of citizens, leaders, and advocates, while description is the work of professional experts like me.  Obviously, this has to be a conversation.  The expert has to ask the community to clarify its values based on the actual tradeoffs presented by reality, and the community has to respond.  And as that goes on, both sides need to be clear about their roles, and respect the role of the other.

Partly because of my science and philosophy training, I tend to police the prescription-description boundary in my own thinking, and dwell in the space of pure description more than many people do — certainly more than most activists do.  A lot of regular readers of HT share that training and that inclination, and some don’t.

For a critique of the futility of living your whole life in this descriptive mode, watching and describing the world but never doing anything, see Shakespeare’s Hamlet.  But the opposite is also futile.  An ethical system devoid of curiosity about objective reality devolves into pure egotism.  Tyrants — whether they lead a nation or an office clique — are people who sift reality and see only what suits their ethical narrative (which, at that point, is really an egotistical narrative) and who forge echo chambers of people who help each other do that.  At the core of the tyrant’s stance is a childlike egotistical wail: “Why doesn’t everyone do as I say?  I see so clearly what needs to be done!”

And yes, everyone has an inner tyrant, including me.  I try to describe that tendency in myself, so that while it will always be in the room of my mind it’s not usually able to set the room on fire.  In fact, that’s exactly why I’m so careful about not letting my descriptive thinking turn too quickly into prescriptions.

Streetcars, for example.  Nowhere in this blog have I said that cities shouldn’t build streetcars if they are sure that they want streetcars.  Some streetcar advocates hear me saying that because they are dividing the world into pro-streetcar and anti-streetcar camps, and I’ve said things about streetcars that don’t sound like enthusiastic advocacy.  I’ve made some descriptive observations about problems raised by the American streetcar revival movement, and I’ve also noticed situations in which streetcars are inferior to buses in their ability to actually get you where you’re going, like this one:

Car blocking streetcars

I would like people to know about these issues so that they make better decisions about what to advocate and why.  That doesn’t mean I want them to decide not to build streetcars, but it may mean, for example, that in deciding whether to support a streetcar, you might need to care about whether it will be in mixed traffic.  It may also mean being very clear, when you’re advocating a streetcar, that you’re not getting anything faster or more reliable than a bus can be.  Again, I say this not because I think cities should or shouldn’t be building streetcars, but because you shouldn’t be deluded about what you’re buying, and what purposes it will really serve.

I have vivid memories of San Francisco Transportation Authority meetings in the early 1990s when the Third Street light rail was under debate.  Activists from the neighborhood had turned out in droves to support the line, but when you actually listened to their testimony, some were talking about “we need rapid transit,” while others were saying “we need rail to stop in every block where it will strengthen our businesses.”  I knew, as an expert, that while this whole crowd appeared to be on the same side of the issue at hand, half of them were not going to get what they thought they were advocating.  They were not going to get a project that served their values.

I may also point out that if you think purely about “extending your rail network” as though your bus network is irrelevant, you can do serious damage to your existing transit system.  For example, in a high-frequency grid, if you break one line of the grid into three consecutive pieces because you want rail in the middle but buses on the extremeties, you may suddenly force many new connections to a degree that could quite possibly will reduce the overall level of mobility in the city.   That thought is relevant, for example, to several cities’ streetcar plans, and to the Crenshaw light rail line in Los Angeles, and to the Gold Coast light rail line (at least its first phase) in Australia.

And yet, sometimes I do sound like an advocate — about transit in general, about protecting transit from traffic, and about congestion pricing.  Am I just falling off the wagon when I say those things?

Well, all scientists (by which I mean broadly “people who try to describe without prescribing”) have this problem.  Sometimes the scientific work of description discovers that something needs to be done if we want to survive and prosper:  Banning DDT, addressing carbon emissions, correcting perverse pricing signals, even building a transit line.  If you’ve followed any of the conversation around climate change, you know how uncomfortable trained scientists can be when they’re required to speak prescriptively.  Their credibility (not just to their profession but also to themselves) has depended precisely on not doing that.  It’s like telling a recovering alcoholic that after all the disciplined work of recovery he’s done, the future of humanity now requires that they start drinking again, just a little.

All I can say is that I feel that discomfort and try to manage it, by marking, as clearly as I can, when I’m prescribing and when I’m describing.  And there are also issues (like climate change) where, quite frankly, practically all experts seem to know what needs to be done to achieve the outcomes that everyone seems to want.  I feel that way about congestion pricing.  It’s just not that hard to explain, to a reasonable person who’s familiar with the idea of supply and demand, that as a motorist you are going to pay for scarce road space in either time or money, and that it’s not unreasonable for some people to choose to spend money to save time.

I do what I can to distinguish between description and prescription when I’m writing.  But frankly, we all need to do the same work when listening.  If your first contact with transit politics is in the context of a fight about whether or not to build a particular rail line, you’re going to hear prescriptive voices on both sides, citing data that’s been selected to match their point of view.  You’re also going to hear descriptive voices treated as prescriptive — which is how some streetcar advocates perceive my comments about streetcars.  One of the most basic disciplines that you can cultivate, as an advocate or leader, is to try to hear descriptive information as descriptive.  This may require you to consciously suppress or bracket the emotional reaction you have, as an advocate, when you first hear it.

Really, none of what I’ve written about streetcars is about streetcars, except insofar as the American streetcar revival movement is a excellent example of a descriptive point that seems important to me.  The point is that “it’s possible to spend a lot of money on transit lines that don’t improve anyone’s mobility.”  I’m not saying you shouldn’t do that.  I am saying that before you that, you should understand this point, so that you’re sure that the line you support does what you want it to do.

That’s what responsible experts do: they help you implement your values.

Basics: Sorting Out Rail-Bus Differences

Do you like trains more than buses, or vice versa?  If so, are you clear on why?  Debates about whether to build rail lines instead of bus lines are heated and often confused.  This post is designed to help you think through what exactly the rail-bus distinctions are, so that you can decide which ones are important to you.  Remember, if you love rail, and win a battle for rail, you may get rail, but you may not get the outcomes you associate with rail.  That’s because most features of transit that matter to how soon you get where you’re going — such as speed, frequency, and walking distance — have nothing to do with the rail-bus distinction.  They are the result of other aspects of how any service, rail or bus, is implemented.

Back in 2009, the then-popular [but now defunct] blog the Infrastructurist asked its readers whether streetcars are better than buses, and why.  Readers came up with 36 responses (listed verbatim here) that formed a good summary of popular perceptions and misconceptions about the rail-bus distinction.

Of the 36 reasons to prefer trains over buses, only six refer to an intrinsic difference between bus and rail technologies.  All the others fall into two categories, which I’ll call misidentified differences and cultural feedback effects.

Misindentified Differences

In your city, the rail system has lots of differences from the buses, including technological differences. But that doesn’t mean that all these distinctions are true rail-bus distinctions.  For example:

  • Propulsion: electric vs internal combustion.   In most North American cities that have both bus and rail, the rail is electric but the buses use internal combustion (diesel, “clean diesel,” or various forms of natural gas).  Electric motors have obvious advantages – in emissions, noise, acceleration, and comfort – but none of these are true rail vs. bus differences.  Rail can be run by internal combustion, and buses can be electric.  If you want to compare your electric rail option with a bus option, compare it to electric trolleybuses.  If you want to compare your internal-combustion buses with a rail option, compare them to internal-combustion rail options such as the Diesel Multiple Unit (DMU).
  • Mixed-flow vs exclusive-lane operation.  Transit speed and reliability are mostly a result of how much you stop and what can get in the way.  Rail is more often run in exclusive rights of way, but some streetcars run in mixed traffic and some buses run in exclusive lanes.  Monorails never get stuck in traffic, but neither do buses in Brisbane, Australia’s busway system.  Most city buses can get stuck in traffic, but so can any streetcar, tram, or light rail vehicle that runs in a mixed traffic lane.  (A major problem for BRT in North America is that people keep taking junkets to Latin America, where BRT is powerful but the economic context is too different, rather than to Brisbane, where they could see high-end BRT working in a wealthy city.)
  • Off-board “proof of payment” fare collection vs. “pay the driver” fare collection.  Fare-collection style has big psychological effects.  “Pay the driver” slows down boarding and is a greater hassle for all concerned.  Some rapid transit sytstems (rail and bus) provide paid areas with faregates, eliminating this delay.  The other solution is “proof of payment,” which means that you buy a ticket on the platform (or already have a valid ticket) but you only show it if a roving “fare inspector” asks to see it.  If you don’t have one, you pay a fine.  Rail is more likely to use “proof of payment” than buses, but there are exceptions both ways, and there’s no necessary link between the rail-vs-bus choice and the fare collection system.  High-capacity bus systems are beginning to shift to “proof of payment” fare collection to eliminate fare-related boarding delay.  UPDATE: San Francisco now uses proof of payment on its entire bus system.
  • Frequency and Span.  Your whole rail transit system may be frequent, while some your buses aren’t, and in that case, you’ll naturally associate frequency with rail.  As we saw here, a good Frequent Network map, which shows both frequent rail and frequent buses, will clear up that confusion.  Buses can be very frequent, while some rail services can run infrequently or peak-only.  (We usually call those commuter rail.)

Cultural Feedback Effects

A community’s attitudes toward rail and bus technologies can easily affect they way they are operated and presented.  In short, people who believe that rail is better than buses will tend to act in ways that make that belief true.  For example;

  • Differences in investment or care.  A community that believes that buses are only for poor people, or that rail is the mode of the future, will under-invest in buses as opposed to rail, producing a difference in quality that will reinforce that belief.  It may also hold bus operations staff to lower standards than rail staff, and encourage other cultural differences between bus and rail operations that become real for the customer, but are not intrinsic to the bus-rail distinction.
  • Perceptions of permanence.  If you don’t stop to think about it, rails in the street will make a service feel permanent, especially if you’re used to hearing people tell you that rails imply permanence.  History clearly shows that rail systems do stop running if their market disappears.  True permanence lies in the permanence of the market, and that lies in the pattern of development [See Human Transit Chapter 14].
  • Perceptions of legibility.  The notion that a bus might do something unpredictable and a railcar won’t is also a cultural feedback effect, typically the result of insufficiently clear and compelling information about the bus network.  It is quite possible to build bus services with such a high level of investment in infrastructure, such as stops and stations, that the routing is as obvious as a rail line’s would be; the Los Angeles Orange Line bus rapid transit system is a good example.
  • Regulatory differences.  Government regulation often enforces different rules for road transport as opposed to rail transport.  These regulations are themselves a kind of cultural feedback, differences in habit and history between agencies that regulate roads and those that regulate rail.  By enforcing different standards and safety requirements, these regulations can cause outcomes that amplify the apparent difference between road-based and rail-based transit.
  • Different potential for mission-creep.  If you build a stretch of road for a busway, there’s always a danger that somebody might try to open it to cars.  If you don’t trust your government to protect the stated purpose of a facility, this can be a major decision factor.  This issue applies, however, to the narrow range of cases in which a road or lane is being built that could be useful to cars but is closed to them.  It is not an issue where the proposal is to reallocate existing roadspace from cars to transit, nor when building a higher-end busway whose design makes it useless to cars even if they were allowed on it.

Intrinsic Bus-Rail Differences

When we set aside those two categories and look at the differences that really follow, intrinsically, from the rail-bus distinction, there appear to be seven, and only the first three of them are always to rail’s advantage:

  • Capacity.  Where demand is high, rail can serve that demand at a higher ratio of passengers to on-board staff, which means that once you absorb the (often large) construction cost, you will be able to offer greater capacity for a given operating cost.  A transit vehicle that’s too crowded to board doesn’t meet any of our seven desires for useful service, so this point is often decisive in favor of rail.
  • Ride quality.   Ride quality in buses is improving, and guided busways may give buses an even more rail-like feel, but new rail systems will probably always have an advantage with their smoother running surface.   Is the smooth ride of rail indispensible to a useful network?  This can be a tough question whose answer may vary from one community to another.
  • Limited energy-efficiency and emissions consequences tied to the difference between tires and steel wheels.  Again, the primary factor governing energy-efficiency and emissions is propulsion (electric vs internal combustion), which is not intrinsic to the rail-bus difference.  However, there is a small range of differences that arise from the physics of steel-on-steel vs tire-on-road operation, and that favor the former.
  • Noise from wheel friction.  Most noise impacts are due to internal combustion, which either rail or buses may use, so that’s a misidentified difference.  Rail transit lines that intersect streets may be required to install noisy crossing signals — a valid response to the extreme weight of commuter rail trains but more controversial as applied to light rail.  These regulatory requirements may be cultural feedback effects.  But rail has a further noise disadvantage that really is intrinsic: the tight fit between steel wheel and rail causes noisy friction when going around curves, especially when going fast.
  • Some variable cost differences.  Broadly speaking, bus-based projects that use portions of existing roadway will be much cheaper than building rail for those same segments would be.  Beyond that, costs for bus vs. rail projects can be hard to compare.  Capital costs for rail include vehicles, while a busway is sometimes run with an existing bus fleet.  Certain bus-rail comparisons in certain corridors may turn up significant differences in operating cost that may be valid in that situation, but need to be checked carefully to ensure that they assume the same factors on both sides.
  • Maneuverability around obstacles is a specific issue for rail in mixed traffic, usually light rail or streetcars.  In mixed traffic, minor obstructions routinely occur in a lane, especially if the lane is adjacent to on-street parking.  People stop in the lane to make deliveries, get into and out of taxis, and parallel-park.  Accidents and breakdowns happen.  If these events block a streetcar, the streetcar is stuck.  A bus, in the same situation, can often go around the obstruction and continue.
  • Ability to extend existing infrastructure.  If you’ve already built rail on a large portion the length of a travel corridor, it may be logical to build rail on the rest, so as not to create a technologically required connection.  On the other hand, busways can often eliminate extra connections because buses can run through the busway but then flow out onto ordinary streets.  In each case, an advantage goes to the technology that makes better use of the infrastructure that already exists, whether road or rail.

Of course, in a particular transit debate, you may not have all of the choices that I’ve articulated here.   Still, it’s important to remember that most of the things you hear about why rail is better than buses are not true in the abstract, as facts of geometry or physics that follow from intrinsic differences between roads and rails.

It may very well be that rail is culturally better than buses in your city, in which case all you’re really saying is that people in your city think rail is better than buses and will therefore tend to act in ways that make that true.  If you’re interested in appealing to your current population, and motivating them to make investment decisions based on their current perceptions about the benefits of rail, that may even be a good reason to build rail even if you don’t need its intrinsic benefits.

But if you’re thinking in longer-range terms, don’t forget:  Attitudes, assumptions and perceptions will change over time.  Physics and geometry won’t.

UPDATE!  See endnotes for this post here!

basics: conceptual triangles

Sometimes, we have to think in triangles.

In the transit world, for example, we know that ridership arises from a relationship between urban form (including density and walkability) and the quantity of service provided.  For example, if we focus on local-stop transit, the triangle looks like this: Continue Reading →

Basics: Some Tools for Small Cities

Early in my career, I did a number of network designs for free-standing small cities in the American West.  These cities, say populations of 30,000-100,000, tend to have a similar set of problems and opportunities, and could probably benefit from a little more theoretical focus.  The same issues arise in most of these cities across North America, Australia, and New Zealand, including: Continue Reading →

Basics: Finding Your Pulse

When transit services are running every 30 minutes or worse, you can’t assume they connect with each other just because they cross on the map.  Schedules need to be coordinated to make connections at low frequencies possible.  The only technique that does this comprehensively is called a pulse or timed transfer.  

A pulse is a regularly scheduled event, usually happening at the same time each hour, in which transit vehicles from a range of routes — usually running every 30 or 60 minutes — are scheduled to all meet together.  A group of hourly local routes, for example, might all come to the pulse point between :22 and :25 after the hour and leave at :30. That way, nobody has to wait more than 8 minutes for a connection even though the services in question are hourly.

The sequence of events at a pulse. Buses arrive, sit together briefly, and then depart. Drawing: Alfred Twu

Often, pulses are organized around a main transit line, such as a trunk bus or rail line that takes you to a nearby larger city.  In these cases, the main line vehicle usually doesn’t dwell as the local buses do, since it’s the most crowded service and hence the most speed-sensitive.   Instead, the locals arrive a few minutes before the trunk passes through, and leave a couple of minutes after.

Pulses are the only way to provide connection wait times that are much, much better than the frequency of the services involved.  A pure pulse is also equally convenient for connections between any pair of lines, and thus for travel in any direction.

For this reason they are used almost universally, in North America, in small-city networks where frequencies are low and often also in suburban areas of large cities.  If you’re in a North American suburb or small city and see a large number of buses hanging out together on a street corner, you’re probably watching a pulse.

I was introduced to pulse scheduling in Portland at a tender age.  I was a teenage transit geek then an undergraduate working part time at TriMet, the transit agency.  This happened to be the period (1979-85) when the lattice of suburban pulse networks was being constructed.

We spent a lot of time thinking about how the pulses interact with each other.  For example, if you have a pulse of buses at Beaverton Transit Center at :05 and :35 past the hour, and one route goes from Beaverton to Sunset Transit Center in 12-14 minutes, how do you schedule the Sunset Transit Center pulse?  Do you set it at :20 and :40, so that this connecting route can serve both pulses but with just a few minutes to spare?  When this route is late, a lot of connections will be missed and a lot of people stranded.  Or do we just set the Sunset pulse at :05 and :35, so that the bus linking the two transit centers has lots of spare time but now has too much time to kill and will tend to arrive inconveniently early for one pulse or the other.  Or do we just accept that this line isn’t going to hit one or the other of the pulses precisely?

In lattices of multiple pulses, the travel times between the pulse points become critical. In this example, if Lines 1 and 2 have different travel times between the two pulse points, the timing may not work well for both of them. Good network design thinks about this problem as routes are being designed.

To do pulse scheduling, we have to plan the pulse schedule as we’re designing the network.  In the two-pulse problem I outlined above, we will think hard about the line connecting the two pulses and ask if we can either make it a little shorter (so that it will get there more reliably in 15 minutes) or a little longer (so that it will get there in 30 minutes without so much time to spare).  I have designed some large networks with multiple pulse points, all designed to work harmoniously.  To do that, I’ve always designed lines between pulse points with the specific goal of making them a certain length.

Pulse scheduling requires an intimate two-way conversation between the planning and scheduling tasks, but not all public transit authorities are not set up to have this conversation.  Sometimes, planning and scheduling are too far apart organizationally and become structurally incapable of noticing and exploiting pulse opportunities.  In other cases, pulses may simply not be the prevailing habit; there may be nobody around who is in the position to suggest them.

The organizational challenge presented by pulsing is, to me, a positive feature of the concept.  Better integration of planning, scheduling, and operations management has many benefits, and if the pulse challenge helps motivate an agency to get there, so much the better.

But pulse scheduling does have some practical limitations.  In particular, it struggles in any environment where the running times are prone to vary a great deal.

Pulses are about managing a low-frequency network, so they aren’t generally needed in inner cities where frequencies are every 15 minutes or better.  Pulses are almost universal in small-city design in North America, because most such cities have little traffic congestion and can therefore run a pulse reliably.  The best big-city agencies also do some kind of pulse late at night, when their services are very infrequent.

But in the suburban areas of big cities, running times vary due to traffic congestion and pulse operations struggle.  I suspect that the difficulty of guaranteeing pulses in these settings is the main reason that big suburban agencies are reluctant to advertise their pulsing too much.  Small-city agencies, which don’t deal with such severe congestion, are more likely to emphasise that at the heart of their network, they have a pulse.

A lattice of interconnected pulse points, all beating as planned in unison or alternation in a pattern that repeats each hour, is a thing of beauty if you can visualize it, especially because if the motion of pulsing suggests the movement of blood through the heart.  It’s like watching the inner life of a large multi-hearted organism.  This can be a nice metaphor for other kinds of thinking about your city.

 

 

1 Ross R. Maxwell, “Converting a Large Region to a Pulsed-Hub Public Transport Network.”  Transportation Research Record, paper 03-4020, p 128.  Original paper here.  

Connections vs Complexity

In my first “basics” post on connections, I explained why a network that requires connections (or as North Americans call them, “transfers”) can actually get people where they’re going faster than a network that tries to avoid them.

But there’s another important reason to plan for connections rather than direct service, one that should be important to anyone who wants transit to be broadly relevant to urban life: Unless you welcome and encourage connections, your network will become very, very complex. Continue Reading →

Basics: The Spacing of Stops and Stations

The unglamorous but essential struggle over the spacing of consecutive stops or stations on a transit line is an area where there’s a huge difference in practice between North American and Australian agencies, for reasons that have never been explained to me as anything other than a difference in bureaucratic habit.  In Australia, and in most parts of Europe that I’ve observed, local-stop services generally stop every 400m (1/4 mile, 1320 feet).  Some North American agencies stop as frequently as every 100m (about 330 ft). Continue Reading →

What Does Transit Do About Traffic Congestion?

This is an old version of this post, which I’ve retained to save its comments.  See the updated version here.

Now and then, someone mentions that a particular transit project did not reduce traffic congestion, as though that was evidence of failure.  Years ago, politicians and transit agencies would sometimes say that a transit project would reduce congestion, though most are now smart enough not to make that claim. Continue Reading →