> Using cars at all isn’t the best we can possibly do.

Granted. But any solutions to that are several orders of magnitude more expensive.

>> Very few people work at full productivity while driving their cars.

> Very few people work at all while driving their cars; their commute is outside of their paid working hours. What is the economic cost of commuting time? This is a serious question.

Employers are not the only economic productivity in a person's life. Child care and raising, socializing with friends, shopping, starting a business, learning new skills.

Point being, nothing economically productive (in the broader sense) is generally happening when someone is driving in a car.

> It would help if you’d elaborate on your proposal with real numbers. Do you want to drive at a higher speed than you can right now, or do you want people you believe to be unskilled to have to slow down compared to today?

The former. It'd be batty to suggest that the current speed limits, justified as the maximum possible speed for a minimally skilled licensed driver, should in fact be lower for some drivers, if we were actually differentiating drivers!

> How fast do you want to drive?

As fast as balances safety concerns! With current performance vehicles, taking into account hypothetical differential speeds using current highway and interstate speeds, I'd say ranges of 70 - 100 mph for the same piece of multi-lane (on one side) road.

> How much faster will your commute be?

Given the above, you'd arrive in 70% of the time at 100 mph, no?

> Your calculus, as presented so far, is completely ignoring:
> 1- the economic costs of safety, or lack of it.

I'm not ignoring it. I'm valuing it as balanced against the economic inefficiencies of alternatives. If optimizing safety were our primary goal, no one would be allowed to drive at all.

> 2- the fact that drivers in a lower speed class would need to be able to react to the faster drivers; in effect they would need to be as skilled in order to share the same roads.

Not sure that completely holds, but I catch your drift. You'd definitely still want to limit speed differentials according to road section, as they effectively do in Germany.

> 3- traffic, not the speed limit, is the limiting speed factor almost everywhere that long commutes exist.

> But hey, if you’re proposing that we make new, separate roads for the multi-speed-class system, maybe I’m for it. Everyone who thinks they’re better drivers and wants to ignore the risks can go drive together on their own road.

I look at traffic as a failure of transportation policy. You're not going to speed your way out of traffic, because it's a throughput problem. So this is irrelevant where speed-limiting traffic is concerned.

>> So between 1994 and 1996 all roads and vehicles became substantially safe?

> No, but both the US interstates and the cars have together become substantially safer over the last 20 years.

I was using those years, when the federal speed cap was removed, to poke a hole in the idea that US speed limits follow intrinsically from any sort of physical principles. I would say that they're more governed by a political process, attempting to balance multiple competing interests.

> I’m curious why you’ve dismissed the Highway Patrol? You’re not objective either, why are you ignoring the people who actually have to respond every time some idiot in a fast car who thinks he has “skill” loses traction and hits someone else or wraps himself around a telephone pole?

Because they're substantially funded by speeding fines? [1]

And if you think local government and officers are blind to their primary sources of revenue, then I've got a bridge to sell you...

[1] https://www.governing.com/gov-data/other/local-governments-h...