Memo: Sustainable Transportation 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 3, 6, and 7 from Jeffrey Tumlin’s Sustainable Transportation Planning.


The authors describe the myriad of ways that human physiology predisposes us to walking and the importance of social interactions at 80 feet or less (where “urban magic” happens). They show evidence that environments where walking is discouraged are correlated with increased rates of obesity and cardiovascular disease. Driving is also shown to increase anxiety and anger, costing society greatly from both health and financial standpoints. Heavily trafficked streets also foster less social cohesion and trust, as well as deterring outdoor exercise that would generate beneficial oxytocin.

To optimize for pedestrian comfort and quality of experience, the authors recommend making paths well-lit, leafy, safe, welcoming, easy to navigate, low in traffic, and full of interesting building frontage to walk past. Tools like walkability audits, tracking surveys, and pedestrian plans that incorporate best practices in wayfinding, traffic calming, accessibility, curb use, and street furniture are essential. Success can be summarized in a Pedestrian LOS and measured in metrics such as distance to crossings, crossing delay, comfort, crossing exposure, and conflict-free crossing time. There is also a recognition of the value of flexible space, such as the use of parking spaces as extended retail fronts or restaurant seating.

In terms of bicycling, the authors make an argument that it is the most sustainable form of transportation from an ecological, social, and economic standpoint. The demand for cycling is increasing, which promotes a beneficial cycle where the activity becomes safer as more people ride. Tactics for increasing the number of cyclists include making it easier to store a bike, planning land uses for a 3-mile average trip length, designing high-quality/dedicated bikeways, making tracks wide enough for socializing, promoting better on-board storage options, and building in shade for bikeways. Further support of cycling requires building a comprehensive bike network, providing clear wayfinding, breaking up intersections into easily navigated sections, providing ample bike parking at destinations, and utilizing the appropriate type of facilities (off-street paths, cycle tracks, bike lanes, or narrow lanes) for the street context.


I always knew that too much dependence on driving and not enough active mobility was bad for health, but it was quite shocking to see the data that showed the magnitude of the risk. It makes me reconsider my own driving habits and start taking daily walks. Unfortunately, I don’t believe most Americans are aware of these statistics, which would partially explain the persistent devotion to driving culture. However, I’m not even certain that an educational campaign (like the campaign for seatbelts in decades past) would be sufficient to change ingrained behaviors here.

I appreciated that many of the specific guidelines and principles for walkways lent themselves to pedestrian comfort and delight, going far beyond basic measures of safety. I feel it is important to make walking as appealing as possible in this way for any chance of it becoming a more widely adopted habit. The discussion of flexible spaces was quite interesting, especially in the context of the COVID-19 pandemic and the significant increase in demand for these kind of spaces by restaurants that wish to operate in a safe manner. Many cities are planning to make these reallocations permanent even after the pandemic, though I am aware there are debates over the “fairness” of turning over so much public space to private establishments.

The recommendation that the right biking facility for a road varies with the speed differential between cars and bikes was surprising to me. I had always thought the best option would be separated bike lanes (cycle tracks), but I can see how their complexity and expense may not always be warranted on certain kinds of roads where bikes and cars move at similar pace. While “sharrows” are mentioned as a design pattern for consideration, I believe the current recommendation on this is debatable due to the increased danger to cyclists as well as the impacts on traffic congestion since cars generally struggle to pass cyclists.

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