[vcarl]

And having speed limits set too low for the road leads to a mismatch between posted risk (the speed limit) and actual risk (the actual speed of cars) to pedestrians. There's evidence that speed limits have no impact on how fast people actually drive[0], so posting a lower speed limit is less likely to have an impact than designing roadways for a certain speed in the first place.

[0]: https://www.ibiblio.org/rdu/sl-irrel.html

[revelation]

Hence the need for speed enforcement. We've come full circle.

[vcarl]

Designing roads properly for the desired speed removes the need for enforcement. And enforcement doesn't mean that people go the posted limit, it just means more tickets.

[sandworm101]

Nope. All sorts of vehicles drive on roads. A motorcycle will always be able to navigate a road far faster than anyone intended. Roads need some sort of speed limit to specify unseen dangers, to communicate to the motorcycle that there is a reason the designer doesn't want him moving at the speed of which he is physically capable.

[dalke]

Yes, there will still need to be speed limits. But if, say, the roads are designed with a 12' lane, the people will tend to drive faster than on a 10' lane. (See http://www.citylab.com/design/2014/10/why-12-foot-traffic-la... .)

I believe vcarl's point is to design the roads for the speed limit, so the speed limit matches what people will perceive to be the right speed for the road. Don't have speed limits which are lower than the perceived limit.

The clumsy way to do this is to put in traffic calming devices. Narrowing the streets is less in-your-face, and comes with other advantages, like cheaper road maintenance. Both are also ways to communicate the appropriate speed limit, in addition to a sign which says the same thing.

[sandworm101]

But setting a limit based on roads doesn't work once we realize that every road is different. We'd need signs everywhere. So we set standard measurements (50kph cities/ 80-highways, special signing for anything else) and build to those standards where practical. So a few roads get slower speeds than perhaps they should, but the standardization brings advantages. Imho good cops should then take it upon themselves to enforce those standards where most appropriate.

Traffic calming isn't about slowing people down. It's about making driving on street-A so painful that people go to street-B. I really like those little roundabouts they use instead of 4-way stops. A motorcycle can basically take a strait line from one side to the other without slowing down. Far easier than a stop sign.

[dalke]

I'm sorry, but I don't understand your comment.

Yes, every road is different. So pay careful attention to the design of every road, rather than following a standard (eg, 12') plan, so people naturally want to drive at the safe speed limit. Design the roads for the speed limit. Don't overdesign the roads, then use signs to force everyone to slow down from what they naturally want to do.

That's still standardization, but based around people rather than a Platonic street design. And it brings its own advantages.

Regarding traffic calming, and quoting from https://en.wikipedia.org/wiki/Traffic_calming :

> Traffic calming consists of physical design and other measures, including narrowed roads and speed humps, put in place on roads for the intention of slowing down or reducing motor-vehicle traffic as well as to improve safety for pedestrians and cyclists.

So yes, it's partially about reducing traffic, but it's definitely also about slowing people down.