Most of the costs of a car are fixed once you own it. Wear and tears per mile is actually small. Insurance is the same for a car driven 7000 miles a year as one driven 30,000. there is a small discount for less than 7000 miles/year, but it is still fixed. Likewise the car payment doesn't change at all.

The IRS has to come up with a fair number that translates all those fixed costs into per/mile. It is a good financial number, but worthless for this discussion.

Not really.

Buying new tires are a thing. Even if you buy cheap tires and get good life out of them (and that combo is...rare, you get what you pay for), that's, say, $400 ever 40,000 miles, that's a cent a mile right there..and tires are usually more expensive than that and don't last that long.

The most obvious cost of wear and tear though is that eventually the car needs to be replaced. More miles = sooner replacement.

Any modern car that is well maintained will last far longer than you will own it. People give up on their cars because their self image needs an excuse to get a new one. A lot of the maintenance cost is time based as well: UV and ozone are destroying rubber parts even while the car is sitting.

It depends on the car, but typically you are looking at $.20/mile for fuel, and $.05 for all other maintenance (including tires).

The average new car payment is something like $550/month. The average used car is somewhat less of course. Most people are making payments. Insurance is $500/year if you have a perfect driving record, many people pay more. These costs have nothing to do with how far you drive.

A few years ago I calculated my actual per/mile cost for my car, it was $.15/month, even though I bought it new (I track every fill up, though at 46mpg my fuel costs are less than average). The car had 200,000 miles on it to spread all the fixed costs across, and had been paid off for a few years.

The point is the marginal cost to drive a car you already own is low.

Considering I was driving 30k/yr at one point while commuting, I can imagine quite a lot of miles, actually.

PS: Your insurance costs are fantasy land. The average US driver pays almost $1500/hr. I haven't had so much as a speeding ticket in a decade and live in a safe small town and am still over $1k/yr.

Lower mileage insurance can help reduce that cost by the way, if you tell your insurer your only adding 2k miles a year to the car rather than 10k miles, they will drop your rates commensurately.

Sub in an eBike for the commuting & errands, its quite doable to go car light or car free (esp. if Car2go, Lime pod or another service is available in your city).

It's only worthless to this discussion if you hold the basic assumption that everyone should own a car.

We've hit peak car in North America. This new generation will see car ownership go down.

Less car ownership on the horizon; 1)Cities are congested 2)The congestion in the suburbs is even worse than driving in downtown 3)For years the solution was to build more highways, but land for doing so is running out 4)Car ownership is no longer cool 5)Ride sharing and renting is become easier (GPS, Internet, Smartphones) 6)Cars have become safer, but the joy or riding in them has been killed. It's like being trapped in an egg carton.

I agree once someone doesn't own the car the numbers change. However if you already have a car the additional marginal cost to drive it on a trip is very low.

The trick would be not to own a car with its high fixed costs, and suddenly the train will be cheap.

That's fair. I do my own maintenance and drive cheap cars. YMMV.

Still, even at the full rate, two people back and forth, it's still cheaper to drive.

Which is pretty normal most places in the US and at least Western Europe unless maybe parking is especially expensive at the destination. Even so, if two of us go from the Boston area to NYC it’s almost certainly cheaper to drive although I almost always take the train because it’s a lot more pleasant. With a family the train would be a relatively expensive alternative.