On: Traffic Simulator

[kqr]

Well, the fixed parameter is people's tolerance for driving time. Everything else (including number of users) will scale up practically indefinitely.

So if you give people more capacity, they will use it until they're back to their trip time tolerance, which is roughly at the same level of congestion.

Is that not the case?

[bobthepanda → kqr]

It is, in the case where roads are free to use.

Price is an extremely effective means of restoring flow to a congested system. Usually, how this works out is that a toll is placed on, say, an existing bridge to finance a parallel or upgraded replacement, and then magically traffic tends to disappear to the point where the new span is no longer needed.

Of course, tolling untolled roads is extremely unpopular.

[throwaway0a5e → bobthepanda]

>Price is an extremely effective means of restoring flow to a congested system.

That's like saying famine is a great way of dealing with overpopulation.

You're fundamentally taking a small subgroup (the trips that are justified despite the increased cost) and saying "look how good things are for them" while completely ignoring everything not in that subgroup. By that same (asinine) logic the SF housing market is great for homeowners.

At best toll roads function as fuzzy rationing (and that isn't great either) where the masses only take the most critical trips.

[bobthepanda → throwaway0a5e]

Roads don’t come for free, and user fees are a very widely used method of paying for them.

Some of the trips brought on by induced demand is just shuffling around of economic activity that would’ve happened elsewhere.

———

You may not like that tolls can re-establish speeds on congested roads, but every solution has drawbacks, including building more free roads.

[kqr → bobthepanda]

Right, of course! Price is a fantastic general way to reduce demand for limited resources so it matches supply.

(It's also a great way to ensure the rich get richer, but that doesn't detract from your point.)

[bluGill → kqr]

No, because the limit isn't driving time, it is things they wany to do. Induced demand is people who can finally do something better. The only time you are right is when you are so far behind that people who used to stay home pick a second best thing because what they really want still isn't in their time tolerance.

Note that building roads is in general not the rigjt answer, build good transit so they don't drive is much cheaper in the long run.

[bobthepanda → kqr]

As an addendum:

Induced demand happens in all types of transportation, but cars are so space inefficient relative to other modes that it does not take a whole lot to get back to where you started, whereas the same cannot really be said of say a subway.