Quote:
Originally Posted by edale
Everyone in urban planning circles knows about induced demand, and the common trope about adding lanes not lessening congestion. But if you add capacity to a roadway, and it remains as congested as it was before, aren't you still moving more cars/people? And doesn't that represent an improvement in regional mobility? Genuine question.
For example, let's say there's a small two lane freeway that's almost always congested during rush hours. The whole freeway gets expanded to 3 lanes, but within a year of opening the expansion, it's just as congested as before during rush hours. Is that a failure, even though that freeway is carrying 33% more traffic? The traffic is presumably shifting from other places, thus removing congestion from other surface streets. Isn't that a win, too?
I'm far from a freeway advocate, but I think the soundbite about additional freeway capacity not reducing congestion is a little disingenuous. Freeways absolutely get needlessly expanded all the time. But sometimes, I believe it is necessary. You have to have right-sized infrastructure or your city/region will not function. Los Angeles has huge freeways, but until recently had very little rail transit. NYC has relatively small freeways, but a vast rail network. Replace LA's freeways with surface streets, or replace NY's rail with bus lines, and both cities would obviously grind to a halt.
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To answer your first question: yes, absolutely. And also: Induced demand has limits, and isn't in itself a bad thing. Inducing new trips is inducing new economic activities and inducing improved connections for people. Ultimately those more cars are allowing more people to go to the places they want to go, when they want to go.
Often the "no improvement" travel time statistic is also only for peak rush hour, when a roadway operates at it's absolute worst. Road widening projects often cannot accommodate peak-hour demand as it is simply so high, especially on roads which are severely congested and see significant amounts of trip-avoidance in peak periods. A widening on that kind or road will still result in substantial reductions in congestion in off-peak periods. At the very least, it allows people to make their trips at more preferred times as they don't have to wait out rush hour any longer.
I know around the GTA, all highways which have been widened in the last 2 decades operate substantially better than they did before, even if they perhaps still bunch up at rush hour.
Where the discussion needs to be held is what kinds of trips we want to induce - do we really want to induce new vehicle trips into a downtown core, for example? It's better to build transit for that sort of condition. It's a lot more nuanced than just "road widening = bad".