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> Or you could just set the speed limit appropriately, at a level that most drivers will naturally conform to. The problem is that such a limit would not be a

> Or you could just set the speed limit appropriately, at a level that most drivers will naturally conform to. The problem is that such a limit would not be a safe one, you would basically be replacing the limit with a sign that posts the rate that people like to drive at.

philsnow 6y ago
There is a real difference, in both actual safety and perceived safety, between divided roads and undivided roads with the same number of lanes. Wider lanes seem (and are) safer than narrower lanes. See https://en.wikipedia.org/wiki/Traffic_calming https://en.wikipedia.org/wiki/Traffic_calming for more. Reasonable drivers conform their driving habits to the environment. Unreasonable drivers should not be allowed to drive.
- waterhouse 6y ago
  > There is a real difference, in both actual safety and perceived safety, between divided roads and undivided roads ... Wider lanes seem (and are) safer than narrower lanes. > [Wiki] Traffic calming can include the following engineering measures ... Narrowing traffic lanes ... Converting one-way streets into two-way streets forces opposing traffic into close proximity, which requires more careful driving What is happening here? Did the engineers forget that they were supposed to optimize for safety, and instead optimized for getting people to slow down? Does the net effect of this improve safety, or worsen it? If everyone drives as fast as they can while meeting some perceived safety level, then does that mean these efforts are unlikely to affect safety and merely to slow everyone down? Is the best set of measures the maximally deceptive set, which looks as dangerous as possible while being as safe as possible?
  - lazyasciiart 6y ago
    > If everyone drives as fast as they can while meeting some perceived safety level, then does that mean these efforts are unlikely to affect safety and merely to slow everyone down? No. It means that people are usually wrong when they judge the safety level of their driving speed on a nice clear road that happens to have pedestrians next to it or trying to cross it, but are more accurate at judging safety when they are primed to expect obstacles, steering challenges, other actors moving not in parallel with them on the road itself. https://www.ite.org/technical-resources/traffic-calming/ https://www.ite.org/technical-resources/traffic-calming/
chillwaves 6y ago
Do you have any evidence of this? My understanding is that speed limits have been largely unchanged for the past 50+ years. Car safety, on the other hand, has increased by a great deal. It seems likely to me that speed limits are conservative when it comes to safety.
- silly-silly 6y ago
  I imagine because they are catering to the lowest common denominator, the human behind the wheel.
  - waterhouse 6y ago
    I suspect it has more to do with the incentives faced by those who set the speed limits. I don't know exactly how it goes. If it's chosen (or heavily influenced) by politicians, I suspect politicians can win some votes by saying they'll improve safety by lowering speed limits (particularly around schools or other places where children might be); while they'd be less likely to win as many votes by saying they'll raise the limits (exposing them to the risk of their opponents calling them reckless/irresponsible). If it's chosen by non-elected officials, that's less of an issue, but something like it may still be there; or it may be that raising the limit and then there being a fatal accident will damage your career, while lowering the limit and irritating everyone will not damage your career.
selectodude 6y ago
The speed limit is (in the USA) supposed to adhere to the 85th percentile rule, that being the speed at which people drive on a free-flowing road with no traffic and no enforcement. Most freeways have speed limits that are probably closer to the 0th percentile than the 85th percentile. I know driving the speed limit on some roads in my neck of the woods would be utterly hazardous.
theonemind 6y ago
The problem is that posting a lower limit doesn't really stop most people from driving faster. Then, some people will obey the speed limit and they become hazards. Other people might believe the posted speed limit tells you about the speed you can expect cars to go on the road. It doesn't. The main safety increase I can see is with respect to commercial trucking. Not all vehicles have the same acceleration and braking ability. But the fact that people just ignore the speed limit is a hard problem. So, yes, as far as is practical, that's the idea. We just post the speed people are driving at.
throwaway0a5e 6y ago
>The problem is that such a limit would not be a safe one, According to who? The minority who wants the limit set elsewhere. Things like "what speed is safe and reasonable" are matters of social consensus. The "experts" can pontificate all they want and the vocal minority can gripe all they want but the median or average person and society at large is always going to be right on matters of social consensus. It's a tautology.
- lazyasciiart 6y ago
  According to dead pedestrians, mostly.
react_burger38 6y ago
Speed limits on the I-15 in Utah have successfully been raised to 80mph without any negative impact to driver safety. Turns out that people do drive at a reasonably safe speed, generally. Source: https://jalopnik.com/utah-raises-some-speed-limits-to-80-mph-because-its-sa-1343843178 https://jalopnik.com/utah-raises-some-speed-limits-to-80-mph...
smabie 6y ago
People like to drive at the rate that is safe. Humans are pretty good at measuring risk. I've driven on many roads in countries that don't have any speed limits. The overwhelming majority are driving a speed that makes sense given the road, driving conditions, etc.

philsnow 6y ago

There is a real difference, in both actual safety and perceived safety, between divided roads and undivided roads with the same number of lanes. Wider lanes seem (and are) safer than narrower lanes. See https://en.wikipedia.org/wiki/Traffic_calming https://en.wikipedia.org/wiki/Traffic_calming for more. Reasonable drivers conform their driving habits to the environment. Unreasonable drivers should not be allowed to drive.

waterhouse 6y ago
> There is a real difference, in both actual safety and perceived safety, between divided roads and undivided roads ... Wider lanes seem (and are) safer than narrower lanes. > [Wiki] Traffic calming can include the following engineering measures ... Narrowing traffic lanes ... Converting one-way streets into two-way streets forces opposing traffic into close proximity, which requires more careful driving What is happening here? Did the engineers forget that they were supposed to optimize for safety, and instead optimized for getting people to slow down? Does the net effect of this improve safety, or worsen it? If everyone drives as fast as they can while meeting some perceived safety level, then does that mean these efforts are unlikely to affect safety and merely to slow everyone down? Is the best set of measures the maximally deceptive set, which looks as dangerous as possible while being as safe as possible?
- lazyasciiart 6y ago
  > If everyone drives as fast as they can while meeting some perceived safety level, then does that mean these efforts are unlikely to affect safety and merely to slow everyone down? No. It means that people are usually wrong when they judge the safety level of their driving speed on a nice clear road that happens to have pedestrians next to it or trying to cross it, but are more accurate at judging safety when they are primed to expect obstacles, steering challenges, other actors moving not in parallel with them on the road itself. https://www.ite.org/technical-resources/traffic-calming/ https://www.ite.org/technical-resources/traffic-calming/

chillwaves 6y ago

Do you have any evidence of this? My understanding is that speed limits have been largely unchanged for the past 50+ years. Car safety, on the other hand, has increased by a great deal. It seems likely to me that speed limits are conservative when it comes to safety.

silly-silly 6y ago
I imagine because they are catering to the lowest common denominator, the human behind the wheel.
- waterhouse 6y ago
  I suspect it has more to do with the incentives faced by those who set the speed limits. I don't know exactly how it goes. If it's chosen (or heavily influenced) by politicians, I suspect politicians can win some votes by saying they'll improve safety by lowering speed limits (particularly around schools or other places where children might be); while they'd be less likely to win as many votes by saying they'll raise the limits (exposing them to the risk of their opponents calling them reckless/irresponsible). If it's chosen by non-elected officials, that's less of an issue, but something like it may still be there; or it may be that raising the limit and then there being a fatal accident will damage your career, while lowering the limit and irritating everyone will not damage your career.

selectodude 6y ago

The speed limit is (in the USA) supposed to adhere to the 85th percentile rule, that being the speed at which people drive on a free-flowing road with no traffic and no enforcement. Most freeways have speed limits that are probably closer to the 0th percentile than the 85th percentile. I know driving the speed limit on some roads in my neck of the woods would be utterly hazardous.

theonemind 6y ago

The problem is that posting a lower limit doesn't really stop most people from driving faster. Then, some people will obey the speed limit and they become hazards. Other people might believe the posted speed limit tells you about the speed you can expect cars to go on the road. It doesn't. The main safety increase I can see is with respect to commercial trucking. Not all vehicles have the same acceleration and braking ability. But the fact that people just ignore the speed limit is a hard problem. So, yes, as far as is practical, that's the idea. We just post the speed people are driving at.

throwaway0a5e 6y ago

>The problem is that such a limit would not be a safe one, According to who? The minority who wants the limit set elsewhere. Things like "what speed is safe and reasonable" are matters of social consensus. The "experts" can pontificate all they want and the vocal minority can gripe all they want but the median or average person and society at large is always going to be right on matters of social consensus. It's a tautology.

lazyasciiart 6y ago
According to dead pedestrians, mostly.

react_burger38 6y ago

Speed limits on the I-15 in Utah have successfully been raised to 80mph without any negative impact to driver safety. Turns out that people do drive at a reasonably safe speed, generally. Source: https://jalopnik.com/utah-raises-some-speed-limits-to-80-mph-because-its-sa-1343843178 https://jalopnik.com/utah-raises-some-speed-limits-to-80-mph...

smabie 6y ago

People like to drive at the rate that is safe. Humans are pretty good at measuring risk. I've driven on many roads in countries that don't have any speed limits. The overwhelming majority are driving a speed that makes sense given the road, driving conditions, etc.