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throw0101a

> Certainly, it rarely ends congestion.

It never ends congestion.

* https://en.wikipedia.org/wiki/Induced_demand

* https://en.wikipedia.org/wiki/Braess%27s_paradox

* https://en.wikipedia.org/wiki/Downs%E2%80%93Thomson_paradox

Want to reduce congestion? Improve transit, build higher density communities, and demolish highways.

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The answer has to be more nuanced than that. Before 2004 the Cuesta Grade near SLO was 4 lanes and permanently congested at commute time. After widening to 6 lanes in 2004, I've rarely noticed congestion at typical congestion times.

It's possible to overbuild roads where there isn't demand for them. But for major metropolitan areas, there are large numbers of people who want to go to similar categories of destinations, and their choice of specific destination is constrained by convenience. If expanding a road reduces congestion (and thus time to reach somewhere), more people will travel farther distances to get there until a new congestion equilibrium is reached.

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