[wastewastewaste]

It is, but usually the meme misrepresents induced demand. While I don't like cars and we should focus on other infrastructure, adding a lane does help.

It does not reduce congestion, but it does now serve more people at this same current congestion level. And those people have come from somewhere. Sometimes from public transport, which isn't really good, but sometimes from some backwater road.

[vidarh]

The bigger problem with induced demand is that it's often poor ROI to add that lane where the demand is highest.

That is, imagine you have a big city. You can add capacity for 1m extra people to travel to the city centre, where there's lots of congestion. Or you find ways to induce demand around the other limits of town, even town current demand is low there.

Odds are you'll pick the first, because it's "obvious" and doesn't require much thinking to see it'd help. But we really ought to look at cost-benefit of the second option too, because repeatedly inducing demand in the centre keeps driving up the incremental cost of further improvements, along plenty of other undesirable second order effects.

[otherme123]

Adding lanes is like getting a bigger cache with the same throughput.

It's obvious at the supermarket: what goes faster, a single cashier processing four short lanes of 10 people with round robin, or two cashiers processing a single lane with 40 people?

Is the city center able to process 1m extra people? If not, it doesn't matter how many lanes you build.

[lmz]

Until more people choose to live further away because the commute is now tolerable with the extra lane (and it's cheaper), and then you're back to square one.