Marco Chitti‘s recent essay on the importance of speed in public transit is a good read. Biology fixes humanity’s basic time budget. Likewise, the amount of time we are willing to spend on travel doesn’t change much, either. As Marco notes, density cannot make transit and transit speed irrelevant. No “15-minute city” based on walking travel times can contain all the services and experiences people need and want on a regular basis. Furthermore, a modern economy requires people to be able to choose jobs over a much larger area.
That said, I think he perhaps dismisses “15-minute cities” a bit too completely. (This is a topic where I disagree with his Transit Costs Project colleague Alon Levy as well.) Density is an important part of the transit speed equation, for two reasons:
- First, the larger the share of destinations reachable in a short walk, the more time people can afford to spend on each longer trip to specialized destinations.
- Second, density makes it possible for those transit trips to be shorter and to serve those destinations more directly.
To be clear, I think Marco and Alon are right that “15-minute-cities” can be, and sometimes are, taken too far. But, at least in a North American context, where extreme segregation of land use and low densities are the norm, “15-minute-cities” are important to emphasize as part of any program of reducing vehicle miles traveled. That said, while land use is important, it obviously isn’t the whole speed story. Public transit needs to be as fast as possible for the trips it is intended to serve. And this topic, I think Marco covers very well.
Maximizing speed for passengers’ trips requires trade-offs in terms of what trips will be served. The easiest way to speed up long-distance is by eliminating intermediate stops, but that eliminates the possibility for many other trips, or requires those making them to transfer. And the best options depend on the built environment and density of the metro area to be served.
Unfortunately, given the US’s and, increasingly Canada’s, extremely high construction costs, which have led to a shift from building fully grade separated rapid transit (the “Great Society subways” of the 1960’s and 1970’s) to light rail and streetcars, the sprawling, edgeless urban areas of North America make higher-speed metros and regional rail especially valuable there, while denser, more contained European cities can sometimes make do with tramways.