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A big reason that the posted speed limit is only loosely correlated with the actual speed driven is because the speed people go is not based on the sign, but ra

A big reason that the posted speed limit is only loosely correlated with the actual speed driven is because the speed people go is not based on the sign, but rather on the design of the road. There are various standards for traffic engineering that define various parts of the road based on the speed expected on them: things like lane widths, curve radii, the presence of fences and guards, and more. A 35mph road will have a smaller turn radius than a 65mph highway, for example. These standards have margins built in to them, obstinately because the standards for faster roads are safer. If, for example, you need a 200 foot turn radius to avoid skidding at 45mph, then the road will be designed with a 300 foot turn radius that would prevent skidding at 55mph, and a 55mph road will have a 400 foot turn radius that would prevent skidding at 65mph. However, what happens is that people will drive at the speed that's safe, not the speed that's posted. People will go 55mph around the 300 foot radius turn that's posted for 45mph. The solution to this seems to be to make the roads designed for lower speeds, or to reduce the safety margin, or as other commenters suggest to add traffic calming measures. I'm pretty sure this would reduce traffic speeds, but I don't know if it would reduce traffic safety.

ThrustVectoring 10y ago
Yup. There's a two-lane road in my hometown that was built and designed for 45 MPH traffic. The rich residents that had trouble pulling out of their driveways onto that road successfully petitioned to get the speed limit reduced to 35 MPH - but this does absolutely nothing to change the design of the existing road. Traffic on that road routinely goes 45-50 MPH on it. If you go the posted speed limit, it feels like you're crawling along.
- thomastjeffery 10y ago
  Wouldn't it be nice if those "rich residents" focused on fixing their driveways instead of forcing everyone around them to alter their way of life?
  - ThrustVectoring 10y ago
    It's not a problem with their driveways. It's a geographic problem, really, with lakefront houses in the 100-400ft strip between an arterial road and the lake. The other side is a steep hill, so you can't make more room, and the main road has to wind a bunch. You don't have the room to put in collection streets and make controlled intersections, so you basically just have to make them wait for a gap and pull out. And as with pretty much any community that has that much value in their house, they're huge NIMBYs.
nvarsj 10y ago
In the UK, where roads are rarely designed for the speed limits posted, it doesn't stop anyone from driving dangerously fast. So I don't really buy this argument. Cars simply handle and drive too well these days for the road to be an impediment. Especially in the UK where most cars have summer tyres, unlike the all-weather tyres common in the US. If anything, it encourages the wannabe-racers to drive fast for a challenge.

ThrustVectoring 10y ago

Yup. There's a two-lane road in my hometown that was built and designed for 45 MPH traffic. The rich residents that had trouble pulling out of their driveways onto that road successfully petitioned to get the speed limit reduced to 35 MPH - but this does absolutely nothing to change the design of the existing road. Traffic on that road routinely goes 45-50 MPH on it. If you go the posted speed limit, it feels like you're crawling along.

thomastjeffery 10y ago
Wouldn't it be nice if those "rich residents" focused on fixing their driveways instead of forcing everyone around them to alter their way of life?
- ThrustVectoring 10y ago
  It's not a problem with their driveways. It's a geographic problem, really, with lakefront houses in the 100-400ft strip between an arterial road and the lake. The other side is a steep hill, so you can't make more room, and the main road has to wind a bunch. You don't have the room to put in collection streets and make controlled intersections, so you basically just have to make them wait for a gap and pull out. And as with pretty much any community that has that much value in their house, they're huge NIMBYs.

nvarsj 10y ago

In the UK, where roads are rarely designed for the speed limits posted, it doesn't stop anyone from driving dangerously fast. So I don't really buy this argument. Cars simply handle and drive too well these days for the road to be an impediment. Especially in the UK where most cars have summer tyres, unlike the all-weather tyres common in the US. If anything, it encourages the wannabe-racers to drive fast for a challenge.