By Dom Nozzi
It is a tactical mistake for those promoting active transportation to seek to demonstrate (or otherwise argue) that building new facilities for bicycling, walking, or transit will result in congestion reduction.
First, cars consume an enormous amount of space (a person in a car consumes 19 times more space than a person in a chair – and up to 100 times as much space when the car is moving). That means that only a tiny handful of motorists are needed to congest a street. Which means that nearly all cities worth their salt have a “congestion problem.” And that those which don’t have such a problem are showing a sign of being sick or otherwise dying, or at least losing attractiveness.
It has been shown over and over again by researchers such as Anthony Downs and Todd Litman that (in any city that is not in decline) we see that space freed up when motorists become non-motorists is almost immediately taken by newly-recruited motorists who had previously been diverted by the congestion (via induced demand, or, as Downs would say, the “triple convergence”).
And when the congestion fails to decline despite lots of time and money spent on non-car travel, the pro-car and pro-sprawl advocates quickly point out that these non-car efforts are a naïve waste of time. And that we should get serious and opt for the realistic (and default) solution: road widening.
Given the above, it seems to me that the progressive tactic is not to claim that promotion of non-car travel will REDUCE congestion. No, I believe it is much better, tactically, to point out that we need to establish ALTERNATIVES for those who wish to escape the (inevitable) congestion: rail trails, connected streets, compact and higher-density housing near jobs, HOT lanes, flex-time work schedules, etc.
As an aside, there are many benefits of congestion for cities (benefits that are undercut when we fight to reduce congestion via the traditional tactics of widenings or signal timing, etc.). But I’ll not get into that now.