Jarrett Walker

Redesigning bus networks

International consultant in public transit network design and policy., Jun 01, 10.

Tagged with urban planning, transit, public transportation, bus service

When planners develop proposals for redesigning a bus network, how do they do it? And when is it necessary?
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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. If you approach bus network design too narrowly, by just adjusting the little things to respond to specific problems of the moment, you tend to end up over time with a network that contains many inefficiencies and is missing many market opportunities.

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 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 feature 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…

Full story: should we redesign our bus network? and how?
Source: Human Transit, May 23, 2010

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