Memo: Sustainable Transportation 3.2

Part of a series of “reading memos” that offer a brief summary of interesting academic content along with my personal reflections. This one covers chapter 8 from Jeffrey Tumlin’s Sustainable Transportation Planning.


The author introduces the wide variety of vehicle modes (combinations of right-of-way design/management, stop/station area design, service model, and vehicle type) that planners can use to fulfill transportation needs in their city. These include buses (local, express/limited, shuttle, and Bus Rapid Transit), rail (streetcar, light rail, commuter rail, and metro rail), ferries, and flexible modes (paratransit and taxicabs/jitneys). Each has their own benefits and should be chosen based on the need for service (rather than for satisfying a desire around the technology itself).

Designing for transit involves making difficult tradeoff decisions, with coverage (having an extensive geographic service area) versus productivity (attracting more riders by providing higher quality service to fewer corridors) being the most common/critical one to consider. The author encourages focus on a few key factors to improve service regardless of mode: Speed, Frequency, and Customer Experience. Following design principles such as not compromising bus routes with deviations, ensuring stops are always comfortable/safe/clean, and promoting legibility (simple/well-defined services with clearly understandable information) for customers can help increase the overall quality of service. A “Transit-First” strategy (government policies, financial incentives, and capital improvements that favor transit) can also go a long way.

Success metrics for transit service can include productivity (passengers per hour), cost-effectiveness (e.g., subsidy per trip), average speeds (including stops), frequency/span, safety, transit mode share, vehicle miles traveled (VMT), customer satisfaction, economic benefits, livability measures, and environmental impacts (e.g., air quality or noise pollution).


This chapter was chock-full of highly practical advice for building high-quality transit systems. I especially appreciated the suggestion to only select a vehicle mode based on service needs, as opposed to technology for technology’s sake – this reminded me of the conversations around Hyperloop as a potentially transformative mobility option, even though there is no clear service need for it yet.

I also appreciated the focus on customer experience, including the discussions on good wayfinding, legibility, comfort at stops, and including customer satisfaction as a key metric of success. This recognizes that successful (and sustainable) public transit needs to be desirable to some extent, to better compete with other modes of travel in people’s decision processes (which use both rational and irrational factors like the social perception of transit).

The coverage versus productivity tradeoff is something I see transit agencies struggling with often. During the COVID-19 pandemic, it seems that most agencies have defaulted to coverage for essential workers or those who have no have no other mobility options, since all the typical commuting/choice ridership demand has evaporated. I’m concerned that the system changes that have been made with this tradeoff will be unsustainable in the long run, as the to-be-expected lower ridership will strain the finances of these transit agencies indefinitely.

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