Racial Justice and Transport Modeling — Human Transit


Two important thinkpieces just appeared that seem to be about different topics but should to be read together.

Christof Spieler, the Houston METRO Board member who drove the 2015 network redesign at the political level, has a piece at Kinder Institute called “Racism has shaped public transit, and it’s riddled with inequities.”  Meanwhile, in Vice, Aaron Gordon takes on “The Broken Algorithm that Poisoned American Transportation,” by which me means transportation demand models.

Spieler outlines how transportation, like everything else, has been forged through many decisions that reflected the values of the time, and how this history has created structures that still produce racially unjust outcomes today.  These structures can be literal infrastructure — like bus lanes designed to be useful for suburban commuters but useless for buses linking inner city residents to opportunity — but they can also be a wide range of bureaucratic and analytic procedures that continue those racially unjust practices in more subtle ways that the people executing those procedures don’t have to notice.

One of those procedures is transportation demand modeling, as Gordon describes it.  The best modeling is not nearly as dumb as the examples Gordon highlights.  But the problem of all modeling is that to show the effects of a proposed action, you have to assume that everything else in the background will remain constant, or at least will continue changing only along predictable paths.

When the modeling process considers many possible futures, the one that is most like the past is called the conservative assumption, as if that means “this is the safest thing to assume.”  This assumption seems calm and rational, attracting many people who would never call themselves conservative politically.  But fact, assuming that the future will be like the past can be crazy if the trajectory defined by the past is unsustainable — environmentally, financially, or (in the case of racial justice) morally.  “Unsustainable” means that it is going to change, and in that case, the “conservative” assumption is really the “self-delusion” assumption.

Transport modeling can’t be thrown out, but it never tells us what to do.  It is a basic logical fallacy to say that “the modeling shows we must do x.”  All modeling insights are if-then statements.  A full version of this statement, which I would like to see at the beginning of every modeling-drive transportation study, is:  “This report shows that if the future matches our assumptions, then you can expect this outcome.  But the future may be like that, and what’s more, your actions will affect whether it does.”



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