“To Predict with Confidence, Plan for Freedom”


The Journal of Public Transportation has a special issue out consisting of thinkpieces by a range of figures in the business.  I’m honored to be there alongside industry leaders like Susan Shaheen of UC Berkeley, Graham Currie of Australia’s Monash University, Kari Watkins of Georgia Tech and Brian Taylor of UCLA, as well as our favorite operations and scheduling consultant, Dan Boyle.

My contribution is called “To Predict with Confidence, Plan for Freedom.”  It basically outlines the argument of my next book, so this would be a great time to hear some critiques of it.  Here’s the opening:

What will urban transportation be like in 10-20 years? How will automated vehicles interact with social and cultural trends to define the city of tomorrow? Will the vehicles of the future be owned or shared? How will pricing evolve to motivate behavior? What will happen to public mass transit? What other innovations can we expect that will transform the landscape? This paper, which is merely the outline of a larger argument, suggests three interconnected answers.

  • We can’t possibly know. History has always been unpredictable, punctuated with shocks, but if the pace of change is accelerating, then unpredictability may be increasing too.
  • We can reach many strong conclusions without knowing. A surprising number of facts about transportation, including some fairly counterintuitive insights that would be transformative if widely understood, can be described and justified solidly with little or no empirical ground, because they are matters of geometry and physics or of nearly axiomatic principles of biology.
  • Prediction may not be what matters anyway. If we abandoned hope of predicting the future, we could still describe a compelling outcome of transportation investment, one that motivates many people who will never care about a ridership prediction or economic impact analysis. We could also predict it in the sense that we can predict the continued value of pi. That idea is freedom, as transportation expands or reduces it.

So if that catches your interest, read the whole thing, and share your comments below!

What If We Called it “Decongestion Pricing”?

Seattle’s KUOW picked up my argument on this today:

Transit consultant Jarrett Walker said the problem is with the name – “congestion pricing.” It’s like the term “death tax,” which was drummed up to discredit the inheritance tax.

Nobody likes death or taxes. Put the two words together and you get a thing politicians have trouble supporting.

Similarly, nobody likes congestion or paying the price for it.

“I’ve suggested the word ‘decongestion pricing,’ because that is what the price buys,” said Walker. “The price buys less congested streets, with more room for all people of all modes to get through. ”

An older, longer, more rambling discussion of this is here.


Basics: Slower Speed is a Service Cut

Does your transit agency have a recent history of operating speed that looks like this?

Source: Portland Bureau of Transportation, Enhanced Transit Corridors Plan, Feb. 2018, page 9

This is the “boiling frog” problem of bus operating speed. In a dense and growing city, it’s not unusual to see speeds falling by about 1% a year, as in this data for Portland’s busiest lines.

If you’re going to analyze how service levels relate to ridership, you have to think about speed. Speed is not just a disadvantage for the customer; slower speeds are also a service cut.

You, the customer, want to go a distance, but the transit agency will pay for your service by the hour. So the quantity of service you experience will be governed by how easily hours turn into distance — in other words, by speed.

So if a transit agency budget grows by 1% a year but speed is falling 1% a year, the customer should expect slower speed and no other growth in service.

When measuring the service quantity that affects ridership, then, look at service miles or km, not service hours.

Portland: Two New Plans to Watch

In most US cities, the city doesn’t control the transit agency, but it does make huge decisions that largely govern whether transit can succeed.  Cities control land use planning, which determines the number of people and jobs that are in places where transit can compete for them, and they control street design, which has a powerful impact on whether buses can operate reliably.  Other city functions, like parking and law enforcement, also have a big impact.

So we get great outcomes only when city government takes a strong leadership role on transit, partnering with the transit agency but also leading in the areas that it controls.

Two new plans out of the Portland Bureau of Transportation show the City of Portland rising to that challenge: the Enhanced Transit Corridors Plannow in public comment, and the Central City in Motion plan, which is just beginning.  While the city has nice transit priority policies and has done a few bus lanes before, we’re now seeing an effort to think more systematically about how to get buses moving again.

Short term indicators are not good:  Ridership is falling and buses are slowing down.  Indeed, bus operating speed is the ultimate boiling frog problem:

Source: Portland Bureau of Transportation, Enhanced Transit Corridors Plan, Feb. 2018, page 9


As traffic grows, speeds fall just gradually enough that the problem never makes the headlines, but a decade of this adds up to a major loss of access to jobs and opportunity.  We’re seeing this rate of drop — around 1% a year — in many growing cities we work in.  This chart shows the city’s busiest frequent bus lines, which collectively add up to a huge share of the transit ridership.

Losing about 10% over a decade doesn’t just mean that people’s trips are longer, but also that 10% more buses must be deployed to maintain the same frequency, consuming funds that could otherwise be spent on growing the network.

Portland’s Enhanced Transit Corridors plan is the first systematic look at this in a long time.  Focusing on the Frequent Network where the stakes are highest, the plan identifies critical points where work must be done to improve performance.  The plan doesn’t choose which transit priority treatments to do where; that’s the work of more detailed engineering.  But it does lay out the big picture and helps to define priorities.  Read the plan and follow it.  (There’s also a survey about it, closing March 26)

Many of the most critical problems are around the edges of downtown, where many routes converge on chokepoints — most commonly the bridges — that are also places where traffic converges.  The Center City in Motion plan is where those problems will be addressed in detail.  There’s also a chance to rethink the role of parallel streets to reduce conflicts between different modes.

This is a big change for Portland.  Too often in the past, the city has plan different modes in isolation — the bike network here, the freight network there, a streetcar plan here, the transit agency’s plans over there — when the best solutions arise only from thinking about all the modes together and how they can best share a limited transportation network.  I’ve worked on studies that do this, in Seattle and Minneapolis, and it’s great to see Portland finally insisting on this kind of thinking.

If you want to get in the weeds, here’s my own starting wishlist for the Center City in Motion plan:

  • Proper transit priority on approach to all of the congested bridges, and between the bridges and the transit mall.
  • Integrated planning of bike and transit to reduce bike-transit conflicts.
  • Reviewing all the east-west transit routings in downtown, possibly consolidating them onto fewer streets.
  • Making better use of the Transit Mall for buses.  At this point I wonder if too many routes have been removed from it and we are not getting enough value from our premiere transit priority facility.
  • Fixing the unacceptable 5-block separation of the two directions of Line 15-Belmont/23rd downtown.

If you live in Portland, get on the mailing list and share your own views!


Excellent Principles for Shared Mobility

Robin Chase, the co-founder of Zipcar, is apparently the genius behind a set of Shared Mobility Principles that came out recently.  I can’t praise them too highly.  Like the founding statements of New Urbanism, these principles cut past the noise and confusion of marketing and show what it would be like to deploy new technologies with the goal of humane and civilized urban life, not just the goal of personal convenience or profit.

Even more important, it’s been signed by many of the main players in the tech transportation field, including Uber, Lyft, Via and many others.  That means you can quote these principles back to them when their actions conflict with these ideals.

As I watch how tech marketing is sowing confusion about public transit, and damaging local officials’ ability to think about it clearly, it’s a relief to see principles such as




From these principles alone you can derive the urgent need to invest more in high-capacity fixed route services covering most of our major cities, except the most low-density or inaccessible fringes.  And the results would be something very different from what I’m seeing every day: Tech campuses built in inaccessible cul-de-sacs, or facing away from the available fixed route service, on the fantasy that in the new world everyone will use little pods that go door-to-door.

Then, when you add:


… we derive the urgent need for shared transportation to be efficient enough to scale.  Efficiency is equity.  An inefficient service will only be available to a few people, and with rare exceptions like ADA paratransit those people will be an elite.   So we can conclude that only a robust fixed route network, aimed at the “middle 80%” but not the elite, can scale to the point of being a tool for equitable liberty.

Anyway, even apart from how it relates to my own passions, this is good stuff. Read, and share, the whole thing.



Orlando and Space Coast: Speaking on April 3

I could have used a picture of an Elon Musk rocket at Cape Canaveral, but I’m more of a botany guy. Photo: Leonard J. DeFrancisci

In my first-ever trip to Central Florida, I’ll be speaking at the Florida Institute of Technology in Melbourne, Florida on the evening of April 3.  Please join me, but you need to register.  Do that here.

Basics: The Ridership – Coverage Tradeoff

By Christopher Yuen

Is your transit agency succeeding?  It depends on what it’s trying to do, and most transit agencies haven’t been given clear direction about what they should be trying to do.

This post revisits a basic topic at the core of transit planning decisions that everyone engaged in conversation about transit should understand.

In the fictional town below, the little dots indicate dwellings and commercial buildings and other land uses. The lines indicate roads. Most of the activity in the town is concentrated around a few roads, as in most towns.

Imagine you are the transit planner for this fictional town. The dots scattered around the map are people and jobs. The 18 buses are the resources the town has to run transit. Before you can plan transit routes you must first decide: What is the purpose of your transit system?

A transit agency pursuing only a ridership goal would focus service on the streets where there are large numbers of people, where walking to transit stops is easy, and where the straight routes feel direct and fast to customers. Because service is concentrated into fewer routes, frequency is high and a bus is always coming soon.

This would result in a network like the one below.

All 18 buses are focused on the busiest areas. Waits for service are short but walks to service are longer for people in less populated areas. Frequency and ridership are high, but some places have no service.

Why is this the maximum ridership alternative?  It has to do with the non-linear payoff of both high density and high frequency, as we explain more fully here.

If the town were pursuing only a coverage goal, on the other hand, the transit agency would spread out services so that every street had a bus route, as in the network at below. Spreading it out sounds great, but it also means spreading it thin.  As a result, all routes would be infrequent, even those on the main roads.  Infrequent service isn’t very useful, so not many people would ride.

The 18 buses are spread around so that there is a route on every street. Everyone lives near a stop, but every route is infrequent, so waits for service are long. Only a few people can bear to wait so long, so ridership is low.

In these two scenarios, the town is using the same number of buses. These two networks cost the same amount to operate, but they deliver very different outcomes.

Ridership-oriented networks serve several popular goals for transit, including:

  • Reducing environmental impact through lower Vehicle Miles Travelled.
  • Achieving low public subsidy per rider, through serving the more riders with the same resources, and through fares collected from more passengers.
  • Allowing continued urban development, even at higher densities, without being constrained by traffic congestion.
  • Reducing the cost of for cities to build and maintain road and bridges by replacing automobile trips with transit trips, and by enabling car-free living for some people living near dense, walkable transit corridors

On the other hand, coverage-oriented networks serve a different set of goals, including:

  • Ensuring that everyone has access to some transit service, no matter where they live.
  • Providing lifeline access to critical services for those who cannot drive.
  • Providing access for people with severe needs.
  • Providing a sense of political equity, by providing service to every municipality or electoral district.

Ridership and coverage goals are both laudable, but they lead us in opposite directions. Within a fixed budget, if a transit agency wants to do more of one, it must do less of the other.

Because of that, cities and transit agencies need to make a clear choice regarding the Ridership-Coverage tradeoff.   In fact, we encourage cities to develop consensus on a Service Allocation Policy, which takes the form of a percentage split of resources between the different goals.  For example, an agency might decide to allocate 60 percent of its service towards the Ridership Goal and 40 percent towards the Coverage Goal.  Our firm has helped many transit agencies think through this question.

What about your city?  What do you think should be the split between ridership and coverage?  The answer will depend on your preferences and values.  No two cities are the same.


Christopher Yuen is an associate at Jarrett Walker+Associates and will be regularly contributing to this blog.