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Their reasoning about the dangers of low speed limits make a lot of sense when you're looking at highways, but I don't think they'd necessarily apply to city or

Their reasoning about the dangers of low speed limits make a lot of sense when you're looking at highways, but I don't think they'd necessarily apply to city or residential streets where there are frequent red lights, pedestrians, etc. Of course, the right thing to do there is probably to configure the roads so that people drive more slowly naturally by narrowing lanes, having trees on the side of the road, etc.

warfangle 12y ago
Or by designing roads around encouraging bicycling and pedestrian safety: - exclusive traffic phase for pedestrians and cyclists (all automobiles receive a red light) at intersections - protected bicycle lanes - no right turn on red - allow the Idaho stop Of course, all of this is predicated on having places where people actually want to walk/bicycle. As opposed to the typical suburban wasteland of concrete, tarmac, strip malls and exhaust fumes. Cars kill. Sometimes even directly.
robert_tweed 12y ago
Part of the idea behind the 85th percentile speed idea talked about in the article is that drivers understand the dangers around them and slow down accordingly. If there are a lot of pedestrians around, most drivers will slow down a lot. Not all of them, but that's why you ignore that last 15%. The one thing the article doesn't mention though is a phenomena of traffic queuing at speed, which happens with average speed cameras. It supposedly increases the chances of collisions, because everyone is going at the same speed, not paying enough attention (because little is changing) and not maintaining enough stopping distance. I don't have citation for this unfortunately. Maybe someone else has a link to the study.
wahsd 12y ago
It doesn't even make any sense regarding highways. Ignoring their embarrassingly flawed standard for setting speed limits based on a percentile of speed limited traffic, there are so many other factors that go into the danger of traffic that are wholly and totally separate from speed. I would argue that the speed is exponentially less significant than the skill and training and experience of the drivers. Take a comparison of the USA with Germany (where there are even roads that don't have a posted speed limit, which foreigners misunderstand for unlimited speed allowed). The USA's per capita automobile death rate is over twice as high as Germany's, in spite of speed limits in general being lower in Germany and there being far more and more generous roads in the USA. That's even with Germany being far more populated than the USA. So you might say, well, Americans drive more. Statistically speaking though, you would think that more driving on wider, bigger roads and in less densely populated areas would lead to less accidents and not more. And then when you look at the statistics of automobile deaths per miles driven you get a 55% higher death rate in the USA than in Germany. There seems to be rather tenuous correlation between traffic danger and speed, at best. The problem is horrible drivers, not speed. We should have a far more rigorous system of driving qualification and recertification. But who are we kidding, speed limits and enforcement have nothing whatsoever to do with safety. Divest the conflict of interest between governmental coffers and speeding tickets and then you can maybe start having a case that the motivations are somehow related to safety. But that's a whole different issue called unfettered government corruption and graft. http://en.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate http://en.wikipedia.org/wiki/List_of_countries_by_traffic-re...
- nostromo 12y ago
  Per-capita is a bad way of measuring auto-fatalities. The US is very spread out and requires a lot of driving. For example, just driving from SF to LA requires more driving than Cologne to Berlin. Per mile driven is much better, and it narrows the US gap with other countries substantially. (The US is slightly lower than Japan, slightly higher than France.)
  - aetherson 12y ago
    Per mile is much better, but also not that good. There are a lot of variables here. How much of driving is at freeway speeds versus how much at lower speeds (where even worse accidents are less likely to cause fatalities)? How good is trauma care in that country (which can turn what would be a fatality in country A into an injury in country B -- and note that part of how "good" trauma care is has to do with how remote from a hospital traffic accidents are)? How modern are vehicles in that country, and what percentage are what kinds of vehicles (air-bag equipped modern cars are much safer than older cars, which are in turn much safer than motorcycles)? What kind of intersection traffic control is there? How good are the roads?
  - apendleton 12y ago
    It depends what you're trying to measure, no? I agree that for the point being made it's not ideal, but I think it's separately noteworthy that in the US, poor planning and more car-dependent lifestyles lead to a higher rate of traffic fatalities because of how much more Americans end up having to drive.
- deleted 12y ago
  [deleted]
- arthurdenture 12y ago
  > The USA's per capita automobile death rate is over twice as high as Germany's, in spite of speed limits in general being lower in Germany and there being far more and more generous roads in the USA. [...] Statistically speaking though, you would think that more driving on wider, bigger roads and in less densely populated areas would lead to less accidents and not more. The relationship between forgiving roads and safety does not necessarily run in the direction you assume. People generally drive at a speed that feels safe, so a road that feels safe will have faster speeds. Faster speeds don't necessarily lead to more crashes, but they definitely lead to a higher rate of serious injuries and fatalities. Given a difference in fatality rate between two developed countries, I'd definitely look at factors like traffic engineering before jumping to the conclusion that, say, Americans are just worse drivers than Germans.

warfangle 12y ago

Or by designing roads around encouraging bicycling and pedestrian safety: - exclusive traffic phase for pedestrians and cyclists (all automobiles receive a red light) at intersections - protected bicycle lanes - no right turn on red - allow the Idaho stop Of course, all of this is predicated on having places where people actually want to walk/bicycle. As opposed to the typical suburban wasteland of concrete, tarmac, strip malls and exhaust fumes. Cars kill. Sometimes even directly.

robert_tweed 12y ago

Part of the idea behind the 85th percentile speed idea talked about in the article is that drivers understand the dangers around them and slow down accordingly. If there are a lot of pedestrians around, most drivers will slow down a lot. Not all of them, but that's why you ignore that last 15%. The one thing the article doesn't mention though is a phenomena of traffic queuing at speed, which happens with average speed cameras. It supposedly increases the chances of collisions, because everyone is going at the same speed, not paying enough attention (because little is changing) and not maintaining enough stopping distance. I don't have citation for this unfortunately. Maybe someone else has a link to the study.

wahsd 12y ago

It doesn't even make any sense regarding highways. Ignoring their embarrassingly flawed standard for setting speed limits based on a percentile of speed limited traffic, there are so many other factors that go into the danger of traffic that are wholly and totally separate from speed. I would argue that the speed is exponentially less significant than the skill and training and experience of the drivers. Take a comparison of the USA with Germany (where there are even roads that don't have a posted speed limit, which foreigners misunderstand for unlimited speed allowed). The USA's per capita automobile death rate is over twice as high as Germany's, in spite of speed limits in general being lower in Germany and there being far more and more generous roads in the USA. That's even with Germany being far more populated than the USA. So you might say, well, Americans drive more. Statistically speaking though, you would think that more driving on wider, bigger roads and in less densely populated areas would lead to less accidents and not more. And then when you look at the statistics of automobile deaths per miles driven you get a 55% higher death rate in the USA than in Germany. There seems to be rather tenuous correlation between traffic danger and speed, at best. The problem is horrible drivers, not speed. We should have a far more rigorous system of driving qualification and recertification. But who are we kidding, speed limits and enforcement have nothing whatsoever to do with safety. Divest the conflict of interest between governmental coffers and speeding tickets and then you can maybe start having a case that the motivations are somehow related to safety. But that's a whole different issue called unfettered government corruption and graft. http://en.wikipedia.org/wiki/List_of_countries_by_traffic-related_death_rate http://en.wikipedia.org/wiki/List_of_countries_by_traffic-re...

nostromo 12y ago
Per-capita is a bad way of measuring auto-fatalities. The US is very spread out and requires a lot of driving. For example, just driving from SF to LA requires more driving than Cologne to Berlin. Per mile driven is much better, and it narrows the US gap with other countries substantially. (The US is slightly lower than Japan, slightly higher than France.)
- aetherson 12y ago
  Per mile is much better, but also not that good. There are a lot of variables here. How much of driving is at freeway speeds versus how much at lower speeds (where even worse accidents are less likely to cause fatalities)? How good is trauma care in that country (which can turn what would be a fatality in country A into an injury in country B -- and note that part of how "good" trauma care is has to do with how remote from a hospital traffic accidents are)? How modern are vehicles in that country, and what percentage are what kinds of vehicles (air-bag equipped modern cars are much safer than older cars, which are in turn much safer than motorcycles)? What kind of intersection traffic control is there? How good are the roads?
- apendleton 12y ago
  It depends what you're trying to measure, no? I agree that for the point being made it's not ideal, but I think it's separately noteworthy that in the US, poor planning and more car-dependent lifestyles lead to a higher rate of traffic fatalities because of how much more Americans end up having to drive.
deleted 12y ago
[deleted]
arthurdenture 12y ago
> The USA's per capita automobile death rate is over twice as high as Germany's, in spite of speed limits in general being lower in Germany and there being far more and more generous roads in the USA. [...] Statistically speaking though, you would think that more driving on wider, bigger roads and in less densely populated areas would lead to less accidents and not more. The relationship between forgiving roads and safety does not necessarily run in the direction you assume. People generally drive at a speed that feels safe, so a road that feels safe will have faster speeds. Faster speeds don't necessarily lead to more crashes, but they definitely lead to a higher rate of serious injuries and fatalities. Given a difference in fatality rate between two developed countries, I'd definitely look at factors like traffic engineering before jumping to the conclusion that, say, Americans are just worse drivers than Germans.