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Comment by bobthepanda | Hacker News Reader

The issue from an urbanism perspective is not really that highways fill up immediately.

The problem is generally selling capacity expansion as "reducing congestion" when it does nothing of the sort. That, and the capacity gets used so quickly that you are very quickly spending yourself into a hole trying to build ever more highway capacity. The thing about a train is that it's very hard to make it so crowded the service degrades due to congestion, at least not within the first 20-50 years.

This black hole of money needed for highway congestion then starts pulling away from other municipal and transportation funding needs.

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But that's true of public transit projects too. They always promise to reduce congestion and never actually do. Congestion charging is probably the only way to really reduce congestion and in many ways the solution is worse than the problem.

And, more than not being a problem, the highway filling up immediately is actually a benefit. Because more people are able and are choosing to travel, to accomplish whatever they need and want to accomplish.

Granted, the externality costs of all that car travel are high. But that's almost a separate issue and one that we really should be solving by a better accounting of costs and additional taxes. It's a shame that won't happen.

It doesn’t reduce road congestion but it does reduce transit congestion. The Second Avenue Subway, for example, decreased loads on the parallel congested Lexington Avenue line by 11%: https://www.6sqft.com/in-just-a-month-second-avenue-subway-e.... It’s displaced 88,000 trips a day, and yet it’s not anywhere near full; a highway expansion would struggle with that amount.

Traffic speeds generally have a floor of how long the equivalent public transport journey is. (If the public transport journey is faster, people will use that instead.) The issue now is that American land use is so out of whack it’s hard to deploy transit widely enough to make that true for the majority of trips.

I think you're on to something with regards to subways in urban environments moving a number of people that a highway expansion would struggle to match. Feels to me like movement of people should be the real metric and, given that, that we should be prioritizing transit investments in places like NYC, San Francisco, and West LA (as opposed to light rail to Azusa).

Downs-Thomson Paradox is also interesting here and relates to your second paragraph. In a built out environment, transit trips and car trips will take roughly the same amount of time, door to door. Transit advocates have used that finding as a way to complain about road projects, but I think it actually is a much more interesting finding that suggests a more multi-modal approach to planning. I wonder how relevant or irrelevant it is for non-built-out environments.

In the US at least, really the complaint from transit advocates is that funding is and continues to be overwhelmingly road-centric, with a small share for transit and basically a pittance for walking and biking.

Usually the issue with suburban transit investment occurring over urban ones is that urban areas are so weak they cannot fund expansions by themselves, and if you want the suburbs to pony up they’ll get their pound of flesh

It'd be interesting to think about ways we could implement congestion control on highways .. every thread I've read implicitly assumes it's not possible

You have to limit demand, which is unpopular, because no one wants to be the one on the losing end of a ramp meter or a toll.

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