Basics

basics: expertise vs. activism

Posted on February 21, 2011 in Advocacy, Basics, Light Rail, Los Angeles, Meditations, Mobility, Philosophy, Rail Transit, San Francisco, Seattle, Streetcars (Trams), Technophilia, Toronto

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 his own knowledge to his client’s values, which may lead him to make different recommendations than he would do as a citizen, expressing his own values. Continue Reading →

what rivers teach about transit

Posted on February 16, 2011 in Basics, Frequent Networks, Maps, Marketing, Melbourne, Public Outreach

Cartographer (and artist) Daniel Huffman is drawing river systems as subway maps. He insists it’s just for fun, but these maps push an important button for me. Continue Reading →

basics: conceptual triangles

Posted on January 23, 2011 in Basics, Density

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

Posted on December 12, 2010 in Basics, Connections, Transfers, Legibility, Maps

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

Posted on November 30, 2010 in Basics, Connections, Transfers, Maps, On-Time Performance, Portland

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.

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

Posted on November 20, 2010 in Basics, Connections, Transfers, London, Los Angeles, Portland, Sydney

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

Posted on November 5, 2010 in 3-newbasic, Basics, Pedestrians, San Francisco, Stop Spacing

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?

Posted on July 25, 2010 in Advocacy, Basics

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 →

Should We Redesign Our Bus Network? How?

Posted on May 22, 2010 in Basics

When planners develop proposals for redesigning a bus network, how do they do it? And when is it necessary?

In 20 years of doing bus network planning around the world, I’ve encountered few systems that don’t have some major obsolete features in their design. Most public transit authorities continually fix small problems in the network but have trouble fixing the big ones.

Making superficial changes to a network is like adding little bits to a house. One by one these bits make sense, but over time they can destroy the design of the house,You may also be doing these little remodels because you can’t face the fact that the foundation is rotting.

Cities change, and every 20 years or so, the bus network should be comprehensively reviewed. Such a project should really include an exercise where you study the city’s demand patterns and design a network on a “blank slate” i.e. deliberately not considering what your network does now. Such a thought process will retain the strongest features of your existing network, but will let you discover new patterns of flow that are a better fit for your system as it is today.

Network design is a process of creative thought, not just analysis. When we rethink a network, we’re doing what a scientist does as he tries to form a new theory:

1. Data Presentation. Look at all the data and try to see NEW patterns in it that the current theory/network misses. (Geographical representations of the data are crucial at this stage. The quality of your data presentation will limit the range of ideas you’ll have.)

2. Creative Thought. Form new ideas that work with those patterns. (This step is creative rather than analytic, and proceeds in unpredictable bursts of inspiration.)

3. Analysis. Test those ideas against the data. Revise or discard those that don’t fit the data well. This is the analytic step, and must not be confused or conflated with the creative step that precedes it.

4. Go to step 2 until you have something you like.

This process is important because great network design ideas solve many problems at once, just as a good scientific theory explains lots of data at once. The single most common mistake in network planning is to think about only one problem at a time, and look only for solutions to that problem. That kind of narrow thinking may be necessary to get from one day to the next, but every 20 years or so (or more often if your city is changing fast) you need to do the larger process I’ve described.

You must also control altitude. The first stage of the work must look at the entire city or service area, to be sure that you solve problems that can be solved only at that scale. Only then can you look at details. More on this here.

My preference is to do this process in an intensive professional workshop setting, similar to the design charrette process in urban design. Typically, about 15 professionals set aside 2-5 days of their time. The people need to be a mix of roving consultants like me and staff of the agency being studied, but they all commit to be open-minded, and are encouraged to think about opportunities and not just constraints.

Sometimes, when running these processes, I’ll ask everyone to name one network design idea that they’d really like to do but that they assume is politically impossible.

The point is to break out of the constraint-dominated thought process that often prevails in the daily life of transit agencies. This isn’t a comment on anyone’s creativity, but rather an observation about the daily experience of bus network planners. Bus agency staffs get very little appreciation, and lots of criticism, no matter what they do, so they tend to become risk-averse cultures. When I run a network planning workshop, my first job is to break through that, and encourage the client’s staff to welcome their own insights even if they may seem politically impossible at first glance.

Core Design Workshop in Yekaterinburg, Russia, 2015.

The workshop room has a large table where we can sit around a drawing in progress. On the table is a base map of our study area, covered with either tracing paper or clear acetate, so that we can draw and revise over and over. The walls are covered with maps of relevant data about our project. There’s also a whiteboard where anyone can sketch out ideas that aren’t ready to go on the map.

(In 2020, of course, we figured out how to do all of this online! It works much better than you’d expect.)

The workshop proceeds through the iterative steps that listed above. We start with a half day or day of just reviewing the data. Then we start brainstorming possible “big moves,” large structural ideas which, if pursued, would lead the rest of the network to take a new form. If we’re planning around a new rapid transit project, then that’s already the “big move.” If we’re just redesigning a bus network, we may think of big moves of our own, such as installing a grid system if that’s appropriate.

Once we have an agreement about big moves, we proceed top-down to address the more local design issues that follow from them. This sequence is important, because the big moves will have the biggest impact. The design of the Frequent Network, for example, is always a big move, and I insist that we hammer out this design before we turn to the less frequent local routes that connect to it.

As we develop ideas, we may do some quick analysis to help us verify them. We also sometimes break for field exploration, as different members of our group go out in cars to check various routings that we’re thinking of.

By the end of the workshop, we may not have total consensus, but we always have a lot more consensus than the client expected going in; we’ve always come up with ideas that were new to everyone in the room. The core workshop isn’t the end of the process, but after this point we usually have a map that bears at least a 70% resemblance to what we’ll finally recommend. More importantly, everyone in the workshop will have ownership of that process, and will see their own influence on it. This, finally, is crucial. One of the hardest jobs of a consultant is to transfer the results of his work to the client agency, so that they see the ideas as theirs rather than as “what that consultant recommended.” Ultimately, the interactive design process is the best way I’ve found of doing that.

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