Archive | April, 2012

some questions on frequent network mapping

@CityBeautiful21 tweets this question about Frequent Network mapping (explained here, examples here and here):

@humantransit In a place that is improving its transit but cannot yet draw a [Frequent Service] map by your ["every 15 minutes all day, seven days a week"  requirements], how would you draw the map?

When a transit agency first sits down to do frequent network mapping, this always comes up.  Not all services are frequent over the same exact span.  Many are frequent all day but not evening or weekend.  This the the normal outcome of a history of route-by-route and hour-by-hour service analysis.

[A Frequent Network policy will gradually enhance those analysis methods by bringing your focus to (a) the entire independent network instead of each route individually and (b) the entirety of the day rather than each hour individually.  Hour-by-hour analysis of routes is especially misleading because ridership at each time of day depends on service availability another time of day; you won't use transit in either direction unless it's available in both directions at times you expect to travel, and if you're not sure when you come back, you care about the abundance and extent of the whole evening service pattern.  This is why cutting evening service — which may have low ridership when analyzed trip by trip — can damage a route's usefulness throughout the service day.]

Meanwhile, how to draw the map?

1.  Start where you are.  If your current frequent service offering is only weekdays all day, then say that.  The map will still be useful.  If you can come up with some kind of minimum evening/weekend service commitment for those route segments (every 30?) then say that as part of the definition of the frequent product.  Meanwhile, you can use your long range planning process to articulate the need for a more robust service span on the Frequent Network, over time.

2.  Consider the larger principle, which is this:  Service that is more likely to be useful to lots of people for lots of purposes, and that are designed to work together as a network, should be more visually prominent.  Service that is highly specialized to a limited market should be less visually prominent, including peak-only services and any service that runs less than once an hour (or even every 30).  It's these occasional service patterns that make transit maps unbearably complicated — a problem easily fixed by ensuring that your map shows those ephemeral route segments but that they recede visually so that the more frequent network stands out.    

It never makes sense to draw a route that runs three times a day in the same line that you'd use for service every 30 minutes all day.  The problem of such maps is the same: you weaken the meaning of a line on the map by using that line to refer to something so ephemeral and specialized, thereby implying that any line on the map may be equally ephemeral and specialized.  So use a different, weaker line for those services.

For some good examples of maps showing all routes in a network, but using this principle that more frequent routes should stand out and less frequent routes should recede, see the full network maps for Portland and Spokane, discussed further in this post.  Here's a slice of Spokane's, where the red lines are frequent and the fainter pink lines are peak-only:

Spokane slice

… and of Portland's, where a wider line is Frequent and peak-only lines are dashed with a white number bullet:

Trimet slice

Full maps here:  Spokane.  Portland.

In both examples, more broadly useful services are more visually prominent.  Peak-only services recede (a thin pink line vs a wide red one in Spokane, a dashed line in Portland) so that you can see them but won't be distracted by them when you want to see the all-day network.  Both maps also highlight the Frequent Network in different ways.  Overall, I prefer the clarity of the Spokane map, because Portland introduces much complexity by trying to differentiate every route by color.  But both are good design responses to the basic problem, which is: Show me the services that are most likely to be useful!

More on this in Chapter 7 of my book.

san francisco: winning speed and reliability battles

38 GEARY V A HospMajor San Francisco transit lines take longer than they did a century ago, as they have been obstructed by traffic and slowed by heavy passenger loads using (until recently) inefficient pay-as-you-board methods. A New York Times piece by Zusha Elinson lays out the statistics.  

(It's important to clarify, right away, that this has nothing to do with streetcars as a technology.  You could easily be misled by this subtle bit of anti-bus bias:

In 1920, the F-Stockton streetcar carried passengers from the Financial District at Market and Stockton Streets all the way to the Marina at Chestnut and Scott Streets in a zippy 17 minutes. Today a very similar trip on the 30-Stockton, the successor to the F-Stockton, takes a half-hour if the stars are properly aligned.

In general, streetcars replaced by buses have slowed down more, over the last century, than those that remained streetcars, but that's an expression of how much more was invested in streetcars than in buses.  The main lines that use the Market Street Subway — J through N — have picked up or shed just a couple of minutes from their 1920 times, even though back then they ran on the surface along Market St (about 3 miles) while now they're in a subway, effectively functioning as rapid transit.  No such improvements were made for streetcars that became bus lines, so of course their performance deteriorated more.  In fact, the 30-Stockton relies heavily on maneuverability in unpredictable Chinatown traffic; a streetcar in exactly the same traffic, unable to move around obstacles, would be even slower and less reliable.)

The real message of this story, though, is the need to have a conscious intention about the speed and reliability of transit.  Highway planners ruled the late 20th century with their clearly defined notion of "Level of Service" or cars, which mowed down opposition through its simplistic A-F letter-grades.  Just after 2000, the Transit Capacity and Quality of Service Manual sought, at first, to claim this same authority-through-simplification for transit.  But while the TCQOS is a spectacular reference guide, few in the business believe that a single A-F score can capture the many important ways that transit succeeds and fails.

My own work in this area has always advocated a stronger, more transit-specific approach that begins not with the single delayed line, but rather with the functioning of an entire network.  Don't just ask "how fast should this line be?" which tends to degenerate into "What can we do to make those forlorn buses move a little faster without upsetting anyone?"  Instead, ask "What travel time outcomes do we need across this network?"  Or turn it around: How much of the city needs to be within 30 minutes of most people?  – a question that leads to those compelling Walkscore travel time maps, which are literally maps of individual freedom.

A network speed standard would identify necessary speed standards for each service type, but especially for the Frequent Network, because high frequency means greater impact of delay — both on passenger freedom and the agency's bottom line.  We* used this approach in a Seattle Transit Plan study about 7 years ago:

1.  Define the Frequent Network (every 15 min or better, all day, every day), including any segments that are "Rapid" (faster with fewer stops)

2.  Define the policy operating speed standard for each product (frequent local vs rapid)

3.  Map the existing scheduled speeds on each segment against this standard, creating a map with screaming red segments meaning "deficient."

4.  Prioritize interventions to improve transit speed based on those deficiencies.  

This is quite different from a classic cost-benefit approach in which we count the riders currently on a segment and assign value based on their total travel time saved, because it acknowledges that (a) a dysfunctional segment is probably driving away customers regardless of how many are on it now and (b) the outcome is the network, not just a single line.

We had a lot of success with this in Seattle at the time.  Once the deficiency map was drawn, engineers noticed segments that they hadn't identified as problems before, and went to work on fixing them.  Note too that the method cleanly separates problem from solution.  Don't start with what you think is possible.  Start with what you need.  Define the absence of what you need as a citywide problem that affects the whole network.  Then fix those deficiencies.  If you're going to go to war with three businesses over "their" strip of on-street parking, you're more likely to break through the "big agency attacks struggling small business" frame if you're defending the entire city's transit system.  

Remember: a line is only as reliable as its least reliable point, and a journey through a network is only as reliable as the least reliable of its lines involved.  So one localized problem affecting speed and reliability (such as stops too close together) actually affects a vast area, and drags down public expectations for an entire network product.  If it costs the agency money (as slower service always does) then it's also a direct detriment to the overall abundance of transit service.  That's the frame in which you win battles over three on-street parking spaces, a signal phase, or even an entire tranist lane.

San Francisco's Transit Effectiveness Project is, to a great extent, the culimination of exactly this thought process.  I remember in the 1980s or early 90s a time when Muni proposed to eliminate just one consequential bus stop;  17th & Mission.  The story became: "Big, bad transit agency launches personal attack on the people and businesses at 17th & Mission."  The TEP has worked to change that conversation, emphasizing that on high-frequency services, the speed of every segment is part of the whole city's transit outcomes.  The same process has made it easier to do a range of other locally-hated citywide goods such as removing parallel routes that were too close together.  

Does your city's transit system have a similar project underway, one that moves beyond route-by-route analysis and looks at how every speed/reliabilit deficiency harms the whole city's transit system?


*I was with Nelson\Nygaard at the time.  The project was the City of Seattle "Urban Village Transit Network" study of 2004, which became a foundation of the Seattle Transit Plan.

vancouver: the frequent network revealed

Vanc FTN slice
One of North America's most advanced transit agencies, TransLink in Vancouver, has finally published a Frequent Network Map as well as a page explaining why that map is important:

This 15 minute or better service runs until 9 p.m. every day, and starts at 6 a.m. on weekdays, 7 a.m. on Saturdays and 8 a.m. on Sundays. This level of service might be provided by one or more types of transit, such as buses or SkyTrain.

People traveling along FTN corridors can expect convenient, reliable, easy-to-use services that are frequent enough that they do not need to refer to a schedule. For municipalities and the development community, the FTN provides a strong organizing framework around which to focus growth and development.

As longtime readers know, I've long advised that high frequency services must stand out from the complexity of a transit map, and be promoted separately, so that people can see the network that's available to people whose time is highly valuable.  Many individuals, and a few agencies, have drawn Frequent Network maps as a result.  For more, see the Frequent Network category.

Meanwhile, this is a hugely important moment for Vancouver, especially because of the way the Frequent Network can organise future land use, and help everyone make better decisions about location.  This map should immediately go up on the wall in every city planner's office, and in the office of every realtor or agent who deals in apartments.  It's far more useful than, say, WalkScore's Transit Score in showing you the actual mobility that will arise from your choice of location, in the terms that matter to you.