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Is Every Speed Limit Too Low?

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Re: Is Every Speed Limit Too Low?

#101

Post by jpollock »

malchow wrote: post #23
wahsd wrote: post #7

Earlier quoted context omitted.

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 compa…

The data in the Wikipedia article you cite can also be sorted by road fatalities by 1 billion vehicle/kms. This accounts for variance in population, auto ownership, and amount of driving. Country and traffic fatalities per 1b veh/kms. United Arab Emirates 310 Brazil 55.9 Slovakia 24.5 South Korea 22.8 Bulgaria 19.1 Estonia 17.5 Cyprus 16.7 Czech Republic 15.7 Malaysia 13.8 Spain 8.5 New Zealand 8.3 Japan 8.3 Belgium…

In New Zealand, the posted speed limit is often too high for the road. If you drive the speed limit, YOU WILL CRASH AND DIE - frequently taking another car with you.

This is because:

1) Very few divided highways 2) Blanket speed limit of 100kph on open roads 3) Fun road obstacles - hairpin turns, single lane bridges, blind corners and no shoulder drops down cliffs.

Re: Is Every Speed Limit Too Low?

#102

Post by peatmoss »

dragonwriter wrote: post #75
peatmoss wrote: post #64

Earlier quoted context omitted.

Generally, worth taking government reports with a grain of salt. I've participated in a few, and the standards are often much lower than peer-reviewed articles. That said, on a quick skim, I don't see anything that strikes me as being obviously wrong / overturned (FHWA was 1997). But, I also don't see either source providing justification for driving faster. Both reports seem to accept this (in fact, this is about as…

> If people respond to a combination of law and roadway design (perhaps leaning more heavily on the latter), and we want behavior in line with law, what should we do? Ease the law or change the roadway design? Or change the context in some third way (e.g., enforcement)? The thing with roadway design is that the roadway designs which enourage higher speed are generally the same ones that are safer at any given speed,…

Enforcement is certainly part of it (planners and civil engineers make jokes about the ever-changing number of "E"s involved in planning--engineering, enforcement, education, encouragement, entomology, et cetera). From my own experience, enforcement is the number one thing people ask for at public meetings, and the very last thing they are willing to pay for. Enforcement is crazy expensive.

Technology, as you point out, more broadly deployable, as well as cheaper and less likely to discriminate. For that reason, I actually kind of like speed / red light cameras. However, they are wildly unpopular to the point of being made illegal in many places. Plus, I think there are legitimate concerns about surveillance aspects of our newly smart cities.

With respect to "safer at any given speed" designs, I think you have to consider that, in order for safety to hold, you need to make some unrealistic assumptions about other factors remaining constant. Also, many of those so-called safer designs really do everything possible to eliminate other kinds of roadway users from the mix.

An automobile monoculture isn't very robust, and it also assumes the wrong units of analysis. Traffic engineers used to measure mobility in vehicle throughput. Amazingly, if you shift your units of analysis to people, monoculture looks less compelling. And that's even before you consider physical activity, environmental externalities, and a raft of other issues.

Re: Is Every Speed Limit Too Low?

#103

Post by moneybags4 »

The lower the speed limit, the easier it is to generate traffic ticket revenue. It's a money game. In California, they tell you that whatever the judge tells you your traffic ticket fine is, say $100, your total is 6 times that when administrative fees are added in.

Re: Is Every Speed Limit Too Low?

#104

Post by jchrisa »

I'd trade a reasonable (15-20mph) speed limit on city streets if it meant people could blast it on the highway.

It's silly to me that so much of the speed limit conversation is around highways, when really the dangerous streets are the fast non-highways (where you see the unfortunate folks walking in the shoulder.) If anything we should slow those down so people don't go faster than 30mph, if we want them to be safe environments for walking.

Sure, speed up the freeway all you want, but don't conflate the freeway's inhumane paved wasteland with every street.

Re: Is Every Speed Limit Too Low?

#105

Post by nilkn »

peatmoss wrote: post #15

This article ignores a lot of peer-reviewed literature from planning, public health / injury prevention, and civil engineering in favor of some folksy wisdom of a lieutenant cop. A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. The article weakly, and quietly made an argument that I do agree with. Namely, roadway design needs to accompany speed limits to ensure…

Correct me if I'm wrong, but the studies you're referring to are examining speed, but not speed limits. It doesn't seem to me that the two are equivalent.

This might be another "tantalizingly counterintuitive" observation, but raising speed limits may not necessarily make everyone go faster. What it might do, though, is make people more courteous to each other.

As an example, if the speed limit is 50mph and you're going 50mph and someone is tailgating you, the fact that they're tailgating you probably frustrates you and makes you less likely to speed up or switch lanes. In fact, depending on your personality, it might make you mad enough to slow down or brake check them. However, if you're going 50mph because that's the speed you're comfortable with, but the speed limit is 65mph, you'll probably still be annoyed at somebody tailgating you but you might also be more sympathetic and hence less likely to do something passive aggressive.

This is, of course, all speculation.

Re: Is Every Speed Limit Too Low?

#106

Post by quantgenius »

peatmoss wrote: post #15

This article ignores a lot of peer-reviewed literature from planning, public health / injury prevention, and civil engineering in favor of some folksy wisdom of a lieutenant cop. A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. The article weakly, and quietly made an argument that I do agree with. Namely, roadway design needs to accompany speed limits to ensure…

The article repeatedly mentions that there is very little correlation between posted speed limits and traffic speed. He goes to great pains to explain that traffic speed seems to be independent of speed limits. The paper you quote states that there is a correlation between accident frequency/severity and actual speed not speed limits. The argument in your comment is based on precisely the fallacy that the article says most people unfortunately fall for, which is that there is in fact a strong correlation between posted speed limits and traffic speed.

Re: Is Every Speed Limit Too Low?

#107

Post by mrgriscom »

peatmoss wrote: post #15

This article ignores a lot of peer-reviewed literature from planning, public health / injury prevention, and civil engineering in favor of some folksy wisdom of a lieutenant cop. A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. The article weakly, and quietly made an argument that I do agree with. Namely, roadway design needs to accompany speed limits to ensure…

I'm annoyed that the taboo thing to say in this discussion is whether increased traffic fatalities is always an inherently bad thing. When you're talking about societal-scale policy, it's impossible to make anything 100% safe; rather, it's about acceptable trade-off in risk. We could make a universal speed limit of 10mph and traffic deaths would probably vanish, but we don't because the impact on transport is too great. People like to brush off this argument with "should someone die just so you can get to work 5 minutes earlier", but if you start multiplying those 5 minutes by millions of people, there is an actual trade-off to consider.

Re: Is Every Speed Limit Too Low?

#108

Post by dragonwriter »

gaius wrote: post #89
dragonwriter wrote: post #83

Earlier quoted context omitted.

> Let's not forget that the speed limit was never about safety. It was about saving fuel in an oil crisis. The establishment of the national maximum highway speed limit of 55mph was about that. Speed limits more generally (which predate that by quite a long time), not so much. EDIT: As it has been accurately pointed out that the above response is US-centric, more generally: the establishment of reduced speed limits i…

You know there are cars outside America? http://news.bbc.co.uk/onthisday/hi/dates/stories/december/15...

> You know there are cars outside America?

Sure, that doesn't change the fact that your statement upthread is still generally wrong. But I've updated my response to it to be more general and less US-centric.

Re: Is Every Speed Limit Too Low?

#109

Post by apendleton »

nostromo wrote: post #17
wahsd wrote: post #7

Earlier quoted context omitted.

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 compa…

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.)

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.

Re: Is Every Speed Limit Too Low?

#110

Post by apendleton »

dfxm12 wrote: post #77
saticmotion wrote: post #65

I didn't get this from the article, but are there no automated cameras in the USA? In Belgium there are tons (I pass 5 on the 10 minute drive to my girlfriend), but they're a joke. If people know the road they're taking, they drive however fast they like, until they get near a camera. They slow down until they're out of reach and then speed up again. Also only about 1/3 actually have a camera in them, but they get ro…

In the US, automated cameras are generally limited to capturing people driving through red lights, if they are used at all.

In many urban areas there are speed cameras as well. I live in Washington, DC, and there are lots.
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