[Dylan16807]

Your common sense is wrong here. If you replace speed limits with "go a safe speed" then people don't go faster indefinitely, they'll find a speed that depends on road design. It doesn't escalate, and it's only notably faster than the speed limit when something has gone wrong with the road planning.

[jfk13]

You're ignoring the fact that many people's perception of what is "a safe speed" is not at all reliable. (Compare: what percentage of people would claim to be better-than-average drivers? https://www.smithlawco.com/blog/2017/december/do-most-driver...)

We have speed limits because trusting people to "go a safe speed" doesn't work, in general.

[Dylan16807]

Objectively, the group settles into a particular speed.

It's based on both safety and perceived safety, and it's not perfect, but it works out pretty well.

If the road is designed properly it's the top few percentile that you need to restrain, not the masses.

If you make a super wide straight shot of asphalt down a residential neighborhood, and people go too fast, that's the road designer's fault.

[jfk13]

> it's the top few percentile that you need to restrain, not the masses

And how do you propose to "restrain" them, if not by enforcing a speed limit?

[alistairSH]

I don’t think anybody is arguing speed limits should be abolished. At least not in any general sense. But, it’s plain enough to see that speed limits on some roads are wrong.

I-495 in VA is a prime example. It’s posted at 55mph and traffic regularly flows faster (or slower, during rush hour). It really needs variable limits based on traffic volume instead of a dumb 55.

[jfk13]

Dylan16807's comment about

> If you replace speed limits with "go a safe speed"...

sounded to me like a suggestion that speed limits could be abolished in favour of a "use your judgement" rule, which I don't think is a sensible idea.

[Dylan16807]

It wasn't.

[Dylan16807]

I'm not suggesting getting rid of speed limits.

I was objecting to the idea that there is no natural speed, and that the group will "just escalate". Nothing else.

[klyrs]

As we're sitting calmly, reasoning about safety, sure. But when the rubber meets the road, you get problems. People learning how to drive don't know the limits of their vehicles; hope you like dead teenagers. Then, you've got somebody in a hurry to get someplace, and their cost/benefit analysis says going an extra 30mph is totally worth the 2 minutes it will shave off their trip.

[cycomanic]

You obviously have not seen any of the many posted videos of some guys racing on public streets. Or are you saying the natural speed is a personal thing and everyone should be allowed to drive as fast as they personally feel comfortable with?

[alistairSH]

There are outliers in any group. Nobody is debating that. All we’re saying is roads tend to have a speed where the vast majority of drivers are comfortable and they’ll tend to go that fast.

Most times you’re on a road and traffic is flowing significantly faster than the posted limit, either the limit is wrong or the road is poorly designed and not fit for purpose. And that happens a lot in the US.

[jjav]

> You obviously have not seen any of the many posted videos of some guys racing on public streets.

Speed limits are supposed to be set to the 85th percentile of natural flow speed for the road.

The very few people racing on public streets are well above the 85th percentile, so that's a straw man argument.