The fact of the matter is that it's absurd to transport people in a dense environment 25'x10' apart, one at a time, all going back and forth to the same exact two places five days a week for 40+ years. Trains let you fit way more people in a given area, people who are already heading the same direction, and therefor offer more space for a city to be a city rather than a place for infrastructure.
Until we get to a point where people are able to move easily with high capacity transit, it's irresponsible to waste precious political will to build with the intention of providing low capacity transport for those who can afford a $30k+ car.
that's accounted for in the foot-second metric. by a (very) rough calculation, we'd only need to double road foot-seconds to alleviate most congestion. that's very expensive, since most of these roads would have to go underground or be elevated, but not impossible (elon is trying to do just that for teslas).
i'm not advocating we double our roads, however. i'm just refuting the pithy notion that it's impossible to meet the supposedly insatiable demand implied by "induced demand" arguments.
but yes, let's build way more public transit and smaller personal transport networks (along with taller, mixed-use buildings)! it's definitely more efficient and can be less expensive and stressful.
If you had to pay for road access, you could easily set the price to where demand meets supply, and all roads would have well flowing traffic 24/7.
But of course "induced demand" happens when the price is $0. The same would occur for bread, phones or pianos at that price point.
To make up for that, we can charge people at the entrance point. But charging people time is basically impossible, so money is used instead.
How capacity is provisioned from A to B influences how people choose to move and, over the long term, build homes/workplaces.
Induced demand does not suggest that supply is less than demand - it implies that demand is "flexible" to meet any supply conditions. There is overwhelming evidence of this at work over 50 years and across continents.
As a consequence, the argument is not "why bother?" but rather - "build it in a way that scales". For urban areas, private transport doesn't scale well.
that's the exact interpretation i'm refuting.
of course supply is less than demand. that's because the price of using roads is (perceived to be) zero, but the cost of construction on the supply side is high (and increasing, relative to inflation). it's impossible to meet the demand for free when costs are high.
my point is that this mispricing is a political and cultural choice, not an economic one explained by "induced demand". by using an economic concept for a non-economic market, we fall prey to misinterpreting and misadvocating.
we need to make the price of private transport much more transparent (e.g., real-time pricing) and rein in costs (land prices, legal/regulatory costs) so that we can make better choices in allocating our precious and limited resources (toward more mass transit for example).
(real-time pricing should also be progressive so that roads aren't just for rich people.)
people want more fast, affordable, on-demand, point-to-point private transportation. "induced demand" tells us we're woefully under-providing that demand. we're very far from the desired equilibrium point in nearly every metro area. elon seems to understand that better than a pithy quip might indicate.
along with mixed-use-as-default along transportation corridors, i would prefer more underground trains, dedicated busways, and small personal transport infrastructure (for electric bikes, scooters, etc.) in our cities (particularly in LA), but every effort, including the boring company's, that addresses that overwhelming demand helps.