Archive | April, 2012

what’s wrong with the “transit score”?

Carter Rubin, on Los Angeles Metro's blog The Source, says exactly what needs to be said about WalkScore.com's Transit Score product.  The product is in the news today because of their new ranking of US cities by Transit Score.

Everyone’s favorite mapping tool, Walk Score, has launched a new service called Transit Score and used it to determine what it believes are the best American cities for public transit. The Switchboard blog has a recap and analysis. Los Angeles clocks in at 11, just behind Portland, Ore., and ahead of Denver, Colo. — respectable enough company, I suppose. That said, I do have some constructive criticisms of Transit Score’s methodology.

Excerpt:

To calculate a raw Transit Score, we sum the value of all of the nearby routes. The value of a route is defined as the service level (frequency per week) multiplied by the mode weight (heavy/light rail is weighted 2X, ferry/cable car/other are 1.5X, and bus is 1X) multiplied by a distance penalty. The distance penalty calculates the distance to the nearest stop on a route and then uses the same distance decay function as the Walk Score algorithm.

The first issue that jumps out at me is how Transit Score weights different modes to give a bonus to “better” modes: “heavy/light rail is weighted 2X, ferry/cable car/other are 1.5X, and bus is 1X.” There’s such an incredible diversity of service quality within each mode that this strikes me as an oversimplification. Is the Metro Los Angeles Orange Line really half as “good” as the Boston Green Line — a nice enough line, but it plods along 100-year-old tracks — just because the former runs on rubber tires?

There are arguments either way, and reasonable people can disagree. Those differences, however, are simply glazed over with a simple multiplier. And, I don’t even pretend to understand the 1.5X weighting for ferries and cable cars.

Early last year, when Transit Score first rolled out, I discussed it with WalkScore's Matt Lerner, expanded on this very critique, and suggested a better (though computationally intense) approach.  It involves aggregating the content of their travel time maps – effectively "maps of your freedom" — over all likely destinations from any residence, so the two digit score is actually a percentage, a composite of answers to the question "What percentage of jobs, retail, etc can you get to in __ minutes, on transit, from here?"   It needs refinement, but that's the only truly factual measure of access that could be reduced to a two digit number.

I understand why Walk Score folks settled on this methodology; it's more about the limits of compultational power than any modal bias on their part.  Still, Transit Score is the only WalkScore.com product that I can't recommend.  I love everything else that WalkScore does, but Transit Score assumes that a slow streetcar is better for you than an express bus, and people need to make that decision for themselves.

heatmaps of service intensity

Does it make sense to represent service intensity as as heatmap?  Is the result at least cool to look at?  Xavier Jacques Côté, a programmer the Québec open-data advocacy group Capitale Ouverte, gave it a try with his hometown, Québec City.

More on the origins of this map, and other cool things Xavier did, in French here.

Hat Tip: David Duval, Ville de Québec.

hello from flagstaff, and a factoid

I'm at the Arizona Transit Association conference, which is also the annual conference of the Arizona DOT. Interesting factoid from an excellent presentation by CTAA's Scott Bogren:  In the US, when a local initiative or referendum to raise some tax to fund transit is put to the voters, they pass 75% of the time.

Scott is on Twitter as @CTMag1 … Follow for more of the same!

seattle media cover last night’s event

My fun faux-debate with Darrin Nordahl last night, sponsored by Town Hall and Transportation Choices, has been covered by both the Seattle Times and the online journal Publicola.  Both summarize the question as something like:  "Should transit be useful or fun?"  Put that way, it's easy to say yes to both, but there really are some choices to be made, because often we're asked to sacrifice the useful for the fun.  As I said in the debate, I support all of Darrin's recommendations for a more joyous transit experience, except where the abundance and usefulness of service must be sacrificed to achieve them.

darrin nordahl’s new book

I will be appearing with Darrin Thursday Wednesday night in Seattle, to promote both of our books.  Details in the far-right column under my photo.

For my review of Darrin's previous book, My Kind of Transit, see here.  Note that Darrin is such a classy guy that he links to my review on his website, even though my review raised major objections to that book.

Darrin is a great writer, a keen observer, and a committed urbanist.  While we have utterly different perspectives (compared by Treehugger's Lloyd Alter here and by Slate's Tom Vanderbilt here) we agree about almost everything that really matters.  I look forward to reading and reviewing his new book, and meeting him again in Seattle on Wednesday.

if you invite me to speak …

… be assured that I don't expect this!

Still, a nice gesture from Calgary Transit.  I trust it flashed only briefly, so that nobody missed crucial info about when the next train is coming.

Note to the broadcast media:  I'm much more coherent when you book me after 8:00 AM.

Here's CBC-Calgary's interview with me on an evening drive show yesterday, in which I sound pretty coherent.  I'm not sure I want to share a TV interview the previous day which began at 6:50 am, only 23 minutes after I woke up.

walking in america

Tom Vanderbilt at Slate is doing a series this week at Slate.com on the crisis of walking in America.  He ties it to a range of issues in public health.  It's also an essential part of providing more efficient (and therefore abundant) transit systems.

The first installment is here, the second here.

jane jacobs on transportation: my take

The City Builder's Book Club is in the process of reading Jane Jacobs's seminal 1961 book, the Death and Life of Great American Cities.   For Chapter 18, which deals with transportation, I did a guest post for them designed to kick off their discussion.  It's there, but also here:

Chapter 18: "Erosion of cities or attrition of automobiles?"

The frame of the question is striking: “Erosion of cities or attrition of automobiles?” Both key terms, erosion and attrition, warn us of a gradual process, a process we might not notice as we focus on the shiny revolution of the moment.

They warn us too, that the causes will be multiple and probably untraceable. Jacobs is adamant that the automobile itself didn’t cause sprawl, just as it didn’t cause traffic congestion; the horse-and-buggy era already offered the possibility of both. So, the attrition of automobiles, as it’s achieved, will have many causes and effects. Each needed but compromised revolution – market-based parking, congestion pricing, major transit, complete streets, road diets – will take due credit for this attrition, but it will really happen through individual choices, and of course the liberation from habit that comes only from the turning of generations.

Early on Jacobs attacks Corbusier for failing to run the numbers on the freeways that were supposed to serve the massed apartment towers of his Radiant City (left). The free flowing traffic in his drawings would have been gridlock, and “his vision of skyscrapers in the park degenerates … into skyscrapers in parking lots.” Corbusier’s freeways are “embroidery,” – surely an insult to that delicate craft – adding a mood or symbol of transportation rather than providing actual mobility. Many urban “visionaries” still do that, of course, implying that a new transportation tool will be so cool to ride or drive that nobody will care if it provides the volume and efficiency required, or fits into a network that will get everyone where they need to go.

Like many urbanists, Jacobs is not very interested in how public transit works, even though it is clearly the mode that must grow as the role of cars gradually shrinks. To anyone who values pedestrians, the mode that delivers as pedestrians beyond their walking range surely deserves more thought. But what she does observe is astute.

For example, she notes that forcing surface transit to use one-way couplets is a way of sacrificing transit’s needs to those of cars, and causes a gradual loss in transit’s effectiveness. (You need transit in both directions for it to be useful in either, and moving the two directions of service apart reduces the area that can walk easily to both of them.) One way couplets aren’t universally evil. They are an essential feature of downtown Portland, for example, and work well with its 200 ft blocks. But one-way couplets that are further apart are another story, sometimes serving completely different neighborhoods with their two directions.

Still, Jacobs knew, from watching New York streets, something that transportation planners needed several more decades to establish: in a dense and active city that is rich with mobility options, there will be as much car traffic as the city chooses to make room for. Her story about the closure of the roadway through Washington Square Park – which resulted in traffic simply disappearing – is the story of San Francisco’s Embarcadero Freeway 30 years later, and of other road capacity removals from the expressways of Seoul to the boulevards of Paris. The traffic that used the formerly busy road disappears, through countless private readjustments, so long as there is an abundant grid of alternate paths into which traffic can disperse, and other modes, such as public transit, to which it can convert, and other times of day to which it can shift its travel. (Anthony Downs later coined the term “triple divergence” to describe these three universally available paths of dissipation.)

This is how attrition of automobiles works. And apart from grand gestures like a freeway removal, it is mostly the work of small, steady work: little increases in friction to cars that subtly shift a balance. Jacobs coins the beautiful term attrition tactician – which conjures balding men in dark rooms under bright lamps, engineering the moving of curbs by a few inches each year. Only today are we seeing the emergence of the attrition strategist or even attrition visionary – charismatic figures like New York’s Jeanette Sadik-Khan or Sydney’s Mayor Clover Moore who wage the battle on some scale and do not apologize for their feared traffic impacts, nor the imagined devastation to businesses that will result if some people shift to public transit or bicycles.

The charismatic figures have their place, but most achievement is gradual. The doctrine of gradualness that pervades this chapter – and indeed all of Death and Life — is a splendid antidote to all silver-bullet theories of urban transformation, from streetcars to convention centers. Real transformation happens in people’s choices, behaviors and habits. It happens at its own unpredictable pace. We will see it only in silhouette – murky and confused – by looking at transport outcomes, but we will see it directly in the life of the city.

on “pilot” or experimental services

An amazing story from Norfolk, Virginia:

NORFOLK, Va. — Hampton Roads Transit is dropping a trial bus service to the Norfolk International Airport due to low ridership.

The agency said Thursday that the pilot program will make its last runs on April 14. The last bus will leave the airport at 11 p.m.

The hourly service began Feb. 5 and originally was to run for a month. The agency says it extended the service a month but ridership remained weak.

Hampton Roads Transit president and CEO William Harrell says the airport service was a good idea but it needs some work.

I have no basis for an informed opinion about the Norfolk airport service, but I would never recommend trying any transit service for a month, or even two.  Any transit service needs time to find its market.   My usual advice is that you shouldn't try an experimental service unless you're prepared to run it for a year, not only so that it can build ridership but also so that you can see how its performance varies with the seasons.

When it comes to larger network redesigns, in which many route changes occur at once, the message for elected officials is even more challenging.  Redesigns are simply not reversible.  They have to run a full year before you can really assess them fairly, and by then, so many people are used to the new patterns of service that reverting to the old ones would be as disruptive as the intial restructuring was.  If an elected official needs to believe that a restructuring can be done "experimentally," I advise them to vote against it.  Obviously, a year after a restructuring, you'll tinker with things based on the ridership, and even sooner you may have to do small adjustments to handle running time or overloading problems. You'll make larger improvements after you've run the redesign for a year.  But there's no going back to where you were, and in a good redesign, after a year, few people want to.