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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

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 people actually drive the desired speeds. Wide lanes, big setbacks, homogenous environments encourage speeding regardless of what is posted. But let's be clear, we should have our design follow our policy, not our policy follow bad designs that were put in place by roadway engineers of yesteryear. That message seemed to be lost in the race to tell us something tantalizingly counterintuitive. I love "everything we know is wrong" storytelling as much as the next guy, but only when that's actually backed up with solid evidence. Take for example this gem from the article: > “We all speed, yet months and months usually pass between us seeing a crash,” Lt. Megge tells us when we call to discuss speed limits. “That tells me that most of us are adequate, safe, reasonable drivers. Speeding and traffic safety have a small correlation.” That would seem to be at odds with this peer reviewed article (sorry, paywall, but you can read the abstract): > Respectively, they found evidence for an exponential function and a power function between speed and crash rate. Both types of studies found evidence that crash rate increases faster with an increase in speed on minor roads than on major roads. At a more detailed level, lane width, junction density, and traffic flow were found to interact with the speed–crash rate relation. Link to article: http://www.sciencedirect.com/science/article/pii/S0001457505001247 http://www.sciencedirect.com/science/article/pii/S0001457505... Priceonomics's banner ad tells me it is selling a new book titled "Everything is Bullshit." Quite right.

tux1968 12y ago
There is conflicting evidence on the matter. A local (Vancouver) video[1] circulating here had some strong arguments that our speed limits are kept needlessly low. If you're interested in such things, it's a well done video and worth the 15 minutes it takes to watch. [1] http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vancouver-roads/ http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vanco...
- elinchrome 12y ago
  That video only gained traction in social media because it is telling people want they want to hear. It's always important to filter everything you read through "do I want to believe the thesis/conclusion of this?" Because a lot of people throw critical thinking out the window when they want to believe something.
  - tux1968 12y ago
    That's not a refutation of the facts presented in the video though. There seem to be an equal number of people who support the status quo and don't want to look at facts that challenge what they want to hear. The facts should speak for themselves regardless of what each of us wants.
    - DanBC 12y ago
      > The facts should speak for themselves regardless of what each of us wants. But when I'm looking for facts I should prefer well constructed research, and not a documentary.
- peatmoss 12y ago
  Wrote my masters thesis in transportation planning on traffic calming. Peer review or it didn't happen. Not that peer review is perfect, but a viral video with an obvious agenda doesn't do it for me.
  - tux1968 12y ago
    Heh, fair enough to be sure. However the video and the associated article that I linked do in fact reference multiple official studies. Examples: - http://www.fhwa.dot.gov/publications/research/safety/97084/97084.pdf http://www.fhwa.dot.gov/publications/research/safety/97084/9... - http://www.th.gov.bc.ca/publications/eng_publications/speed_review/Speed_Review_Report.pdf http://www.th.gov.bc.ca/publications/eng_publications/speed_...
    - 12y ago
timbre 12y ago
The Priceonomics article's main point is that raising speed limits doesn't (much) raise actual speed, so it's not inconsistent with papers (like the one you linked) that show that increased speed causes more and worse accidents.
- peatmoss 12y ago
  As I said, to the extent that the article made the case for combining speed limits with roadway design, I agree. However, the quote from the Lieutenant was clearly stating that speeding was not the problem. The whole article appears to have been either crafted or embarrassingly not crafted to muddle these two questions.
- cpncrunch 12y ago
  Other research shows that raising speed limits increases accidents, and reducing speed limits reduces accidents. https://en.wikipedia.org/wiki/Speed_limit#Effectiveness https://en.wikipedia.org/wiki/Speed_limit#Effectiveness
  - aetherson 12y ago
    Obviously it's hard to judge studies by one sentence summaries, but some of those papers sound like extraordinary claims. "Speeds declined by 5 km/h. Fatal crashes declined by 12%." Come on, really? We're going to imagine that a 3mph change in speed (at speeds around 80mph) could possibly be causal to a 12% change in fatalities?
    - cpncrunch 12y ago
      I haven't looked at the refs, but you're welcome to. I suspect wikipedia is more reliable than priceonomics.com, although you have to look at the sources yourself to be sure.
clairity 12y ago
speed definitely increases the severity of crashes, but i'm not convinced that it increases frequency. even so, the #1 factor leading to increased frequency of crashes is distracted driving (sorry, don't have time to look up relevant links). if it exists, the correlation of accidents with speed is likely much weaker than with distractedness. if we really wanted to reduce motoring accidents, rather than regulating speed, we'd regulate away everything you can do in a car other than drive (radio, food, shaving, makeup, newspapers, etc.). i'd even suggest that driving fast might cause you to be less distracted because of the higher severity of a crash (would be an interesting research topic).
- Theodores 12y ago
  Maybe we should go back to Cadillac Eldorado 'bullet' style steering wheels (and no seatbelts) which really were as much use as a spike in the middle of a steering wheel.
  - seanflyon 12y ago
    It would reduce the number of crashes. Its essentially the same argument as your comment's grandparent, that we should make the roads narrower to reduce driving speed.
- tbrownaw 12y ago
  i'd even suggest that driving fast might cause you to be less distracted because of the higher severity of a crash And because faster reaction times require you to stay more aware. Unfortunately, trying to find where I heard about this just comes back with a bunch of stuff about risk tolerance w.r.t. financial investments.
reitanqild 12y ago
Mentioned this in another thread and I'm still looking for researh around this topic: A Dutch engineer once told me (back before 2004 I guess ) that they once raised the speed limit on the roads in Netherlands and found that counterintuitively, - average speed decreased. His explanation IIRC was that 1. once people break the rules it doesn't matter how much and 2. when speed limits felt more correct more people respected them. this, according to him, meant that even if some people were driving faster a lot of those who used to break the rules now followed them. I'd still love to know if anyone has any more pointers to research on this and I am fairly sure someone around here knows a whole lot. ( I got some unexpected input in the other thread already.)
- peatmoss 12y ago
  Interesting! Of course the Dutch are also leaders in highly designed shared streets that make the hippest of the hipster urban designers in the US swoon with envy. Unless we're talking about major highway facilities (and perhaps not even then), my hunch is that we're looking at some radically different street design.
- gaius 12y ago
  Let's not forget that the speed limit was never about safety. It was about saving fuel in an oil crisis.
  - dragonwriter 12y ago
    > 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 in many jurisdictions in the early-mid 1970s (including the US national maximum highway speed limit of 55mph) were due to the concerns of saving fuel in an oil crisis, but that is not true of speed limits more generally (either before -- stretching back to more than a century before automobiles existed -- or after the 1970s.)
ameister14 12y ago
I think it's pretty interesting that you advocate for narrower roads and short setbacks because you belive that on roads like this people are less likely to speed. I don't know if people are less likely to speed on those roads; I think it is unlikely because growing up in a small town, people speed on backwoods roads all the time. Still, I'm not sure that this is the case. What I do know is that roads like that are less safe, particularly if you DO speed. So, unless you can show me that making a road less safe for speeding reduces the rate at which people drive, I'm going to keep thinking that that argument is like saying you can't give out condoms to kids because it makes them more likely to have sex.
- TeMPOraL 12y ago
  Risk compensating behaviour[0] is a real thing; the question is whether that effect is significant in any particular case. Making the roads look less safe will make people drive more carefully, but it has to be shown whether this will cause a net decrease of actual crash rate. [0] - http://en.wikipedia.org/wiki/Risk_compensation http://en.wikipedia.org/wiki/Risk_compensation
  - AnthonyMouse 12y ago
    > Making the roads look less safe will make people drive more carefully, but it has to be shown whether this will cause a net decrease of actual crash rate. There is also the matter that many of the ways to make roads look less safe would in actual fact make the roads less safe. At a given speed, narrower lanes increase the probability of a collision. Parked cars on the side of a road increase the probability that one will be hit, or conceal from motorists the presence of pedestrians about to step into the street. People focused on speed are asking the wrong question. The question is not "how do we get people to slow down" but rather "how do we make the roads safer"? Speed is only one variable.
- enf 12y ago
  Most of the recent research on factors affecting vehicle speeds is summarized in http://onlinepubs.trb.org/onlinepubs/circulars/ec151.pdf http://onlinepubs.trb.org/onlinepubs/circulars/ec151.pdf In it, Dimauita et al credit every foot of lane width with a 2 mph increase in vehicle speeds, and Wang et al credit each additional lane with a 6.5 mph increase.
autokad 12y ago
the article repeatedly mentioned: raising speed limits does not raise driving speeds on roads. humans are kind of strange in the fact that they drive at a speed they are comfortable with. also, while that (faster = crash more) may be true, its not the only thing going on. it may be the case (and one argued in the article) that driving speed differences results in more crashes.
- bryanlarsen 12y ago
  "raising speed limits does not raise driving speeds on roads" I suspect that's a temporary effect. The speed people are comfortable at is mostly a learned phenomenon. The more they drive fast safely, the more comfortable they feel. Remember when you first started riding your bicycle? 10 mph was super fast and was super scary. And it is; that's faster than the speeds that the human body was evolved to support.
  - autokad 12y ago
    i didnt keep riding bicycle faster and faster and faster. i got to a point where i was comfortable at that speed...
    - wiredfool 12y ago
      Alternate explanation: You got a point where it's physically very hard to go faster. Most people who ride motorcycles or mopeds do it faster than they would on a bicycle.
      - jdbernard 12y ago
        And yet, as someone who travels almost exclusively by motorcycle, there is a limit to how fast I am willing to go which varies depending on the road I am on. My bike will easily go much faster, and I feel like I could safely command the bike even going fair bit faster, but I am not comfortable going faster on a regular basis.
        12y ago
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Spooky23 12y ago
End of the day, you shouldn't have laws that 80% of the population breaks during the ordinary course if business. I've found myself in vehicles towing trailers where 65 mph was about as fast as I could go. I continuously had cars passing me. If everyone is a criminal, something is wrong with the law.
- cpncrunch 12y ago
  They say 85% break the limit, but by how much? According to a 2003 UK study only 25% of people break the 30mph speed limit by more than 5mph, and only 20% break motorway speed limits by more than 10mph. https://en.wikipedia.org/wiki/Road_speed_limit_enforcement_in_the_United_Kingdom#Effectiveness https://en.wikipedia.org/wiki/Road_speed_limit_enforcement_i...
  - PantaloonFlames 12y ago
    I think you have that backwards. The text in the article was: > they want to set the speed limit so that 15% of drivers exceed it and 85% of drivers drive at or below the speed limit. The citation you provided is roughly consistent with that. The original article also said: > Lt. Megge believes the compliance rate in Michigan to be well under 50%. That's the only part that estimates rates of non-compliance. And it's not 85%.
    - cpncrunch 12y ago
      Actually, the article says “I’ve found that about 10% of drivers truly identify the speed limit sign and drive at or near that limit,”. That is what we were discussing here, not the 85/15 percentile thing. (Sorry I should have said 90% rather than 85%). Of course the article doesn't say what those other 90% are doing. I suspect they aren't all breaking the limit - probably some are going slower than the speed limit.
- rtpg 12y ago
  Well, there seems to be this myth that its OK to speed 5 miles above the posted speed limit, so the speed limit is still useful. It'll just be limiting the speed to 60 instead of 55. As to whether things are enforced that way, that's a different story.
nilkn 12y ago
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.
quantgenius 12y ago
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.
- peatmoss 12y ago
  And yet occasionally lets slip quotes like the one I posted earlier, in which the officer sites anecdata that speed isn't the problem. The article I posted was specifically countering that notion. The broader issue I have with this article is its prescription for bringing speeds and speed limits closer together--namely increasing the speed limits. I think using roadway engineering to decrease the speeds is actually addressing the first order problem.
  - NoPiece 12y ago
    If you are talking about an urban boulevard, then I agree. Engineer the street to lower speeds, and increase safety because there are pragmatic options (roundabouts, speed bumps, more signals and stop signs. But if you are talking about intercity highways, something like Los Angeles to Phoenix to Denver to Des Moines, then just increase the speed limit.
mrgriscom 12y ago
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.
- thrownaway2424 12y ago
  I hate slippery-slope arguments, but I feel that if you are going to advocate the scenario you seem to have advocated, then you can take it a lot further. For example I feel that anyone whose car stalls while crossing the San Francisco-Oakland Bay Bridge should be banned from driving for life. Because every time someone stalls on the bridge at rush hour there's a traffic jam clear back to Reno.
- rtpg 12y ago
  The tradeoff for speeding is stupidly small. Average US worker spends 25 minutes on a one-way trip to work. Lets assume an average speed of 60mph (hint: it's slower). If you went at 70 instead of 60, then you'll save a whole 3.5 minutes. Here(http://webcache.googleusercontent.com/search?q=cache:jWbI1mKY8qgJ:www.nhtsa.gov/people/injury/enforce/speed_forum_presentations/ferguson.pdf+&cd=1&hl=fr&ct=clnk http://webcache.googleusercontent.com/search?q=cache:jWbI1mK...) is a link to a NHTSA presentation on speed limit changes and its effects on crashes. Notably, when states were given control of speed limits, we saw raises from 60-65 to 70-75 mph in some situations, and a 35% increase in fatalities. if we do the whole "life is worth $3M dollars" argument, divide by two because I'm trying to make this favorable to you (even though car fatalities disproportionately affect young people), letting people go 70 instead of 60 could still end up causing almost 10k more deaths per year, so there's $15B in lost value per year. At least I'll get to sleep in for 3.5 more minutes.
  - rokhayakebe 12y ago
spott 12y ago
Respectfully, you didn't read the rest of the abstract to the article you cite, and the next few sentences support what the article says: >Other studies looked at speed dispersion and found evidence that this is also an important factor in determining crash rate. Larger differences in speed between vehicles are related to a higher crash rate. Without exception, a vehicle that moved (much) faster than other traffic around it, had a higher crash rate. Which is the whole point of this article. The article isn't saying that isn't dangerous, it is saying that speed differential is more dangerous than speed. It is saying that speed limits are generally ignored by most people (most people drive some combination of the speed of traffic and the speed they feel comfortable with), however the few people that DO listen to them cause accidents because it makes the differential speed much higher. > A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. This is a horrible starting model. The severity of crashes is physics, but the frequency can't be looked at in isolation. Even the article you cite hints at the fact that the relationship isn't that simple: In figure 1, rural roads with higher speed limits have a shallow linear relationship between crashes and speed, while urban roads with lower speed limits have a much steeper, exponential relationship between crashes and speed. Which counteracts a very simple "speed increases the frequency of accidents".
- peatmoss 12y ago
  Respectfully, I did, and you're failing to acknowledge what I wrote in my initial posting. > it is saying that speed differential is more dangerous than speed. No it's not, the article is saying that a delta in speed is a factor in crash frequency. (And no, I didn't copy paste the whole abstract, because I was posting the part of the abstract germane to the quote I cited from the original article.) > This is a horrible starting model. The severity of crashes is physics, but the frequency can't be looked at in isolation. No, it's still a good starting model. If you read all the way to the end of that abstract, I think you'll see my point: > Without exception, a vehicle that moved (much) faster than other traffic around it, had a higher crash rate. With regard to the rate of a (much) slower moving vehicle, the evidence is inconclusive. So, much faster moving vehicles always had higher crash rates, while much slower vehicles... inconclusive. There's a saying in statistics (George Box) that all models are wrong, but some models are useful. I think you'll find examples where speed isn't a problem, but those aren't the norm. If you're looking for a simple univariate model that goes a good long ways toward explaining vehicle safety, I'd challenge you to come up with a better one than what I've proposed here.
aetherson 12y ago
Let me rephrase what I think your argument is: "I think that we should set speed limits to somewhere around where they are now or lower, and then re-engineer our roads to make it harder for people to speed. This is practical and will save lives, and the evidence supports this." If I'm reading you correctly, I have a number of problems with it: 1. I don't think it's in any way practical to re-engineer roads on the massive scale that would be necessary to do this. If, as asserted, the majority of people exceed the speed limits the majority of the time, you're talking about re-engineering the majority of roads. That's an enormous project compared to resetting the speed limits. 2. You're a bit light on details about what you would do to make people obey the speed limits, but you list as contributing to speeding "wide lanes, big setbacks, and homogenous environments." Leaving aside homogenous environments (are we now talking about re-engineering not only all of our roads, but also all of our cities in general?), I'm sure that making lanes narrower and setbacks smaller would in fact make people drive slower, but would it actually increase safety compared to the counterfactual of not re-engineering and increasing speed limits? I doubt it. Certainly, I don't see evidence for it. 3. Hidden in here is a question of legitimacy. Are current speed limits a result of a social consensus about the speed/safety tradeoff made by an open society? I don't think that there's any convincing evidence that they are. They appear to be a reaction to OPEC and a revenue model for local governments at least as much as they are about a democratic consensus -- and to the extent that they are about a democratic consensus, they seem to be based on one in which the democracy in general was not aware of the deleterious effects of low speed limits in terms of speed differentials. So, look, the situation right now appears to be: a. Roads designed for speed, but with artificially low speed limits leading to inflated danger. And a couple of possible future policies could be: b. Roads designed for speed, with higher speed limits leading to reduced danger compared to a. c. Roads designed for lower speed, with the same or lower speed limits leading to reduced danger compared to either a. or b. It seems like you've jumped to the conclusion that option c is the right one, but I don't know that it is, even granted that it is the safest option.
dwd 12y ago
It also ignores that speed limits are largely determined by what speed would allow you to safely stop if there was an road obstruction (traffic, animal, merging vehicles, etc).
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TheOtherHobbes 12y ago
>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. More than that, it's pure econo-meta - regulation is bad, freedom is good, if you leave people alone they'll behave responsibly, and everyone wins. It's a moral parable (for economic values of 'moral') not a peer-reviewed paper. Here's a newspaper piece that summarises some of the relevant peer reviewed research and draws a different conclusion: http://www.theguardian.com/news/datablog/2013/may/13/speed-limits-reduce-number-road-deaths http://www.theguardian.com/news/datablog/2013/may/13/speed-l...
rrss1122 12y ago
I would not trust the average person with higher speed limits. If they want to be adequate, safe, reasonable drivers, then they should drive at a slower speed and get used to it. I get the feeling that the reason most people who speed do it is because they overestimate the amount of time they'll have to get to where they're going and speed up when they see they're gonna be late.
matdrewin 12y ago
You obviously didn't understand the article. It didn't say that speed wasn't dangerous. It said that speed signs only give us the illusion of safety because the majority of people disregard them anyways.

tux1968 12y ago

There is conflicting evidence on the matter. A local (Vancouver) video[1] circulating here had some strong arguments that our speed limits are kept needlessly low. If you're interested in such things, it's a well done video and worth the 15 minutes it takes to watch. [1] http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vancouver-roads/ http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vanco...

elinchrome 12y ago
That video only gained traction in social media because it is telling people want they want to hear. It's always important to filter everything you read through "do I want to believe the thesis/conclusion of this?" Because a lot of people throw critical thinking out the window when they want to believe something.
- tux1968 12y ago
  That's not a refutation of the facts presented in the video though. There seem to be an equal number of people who support the status quo and don't want to look at facts that challenge what they want to hear. The facts should speak for themselves regardless of what each of us wants.
  - DanBC 12y ago
    > The facts should speak for themselves regardless of what each of us wants. But when I'm looking for facts I should prefer well constructed research, and not a documentary.
peatmoss 12y ago
Wrote my masters thesis in transportation planning on traffic calming. Peer review or it didn't happen. Not that peer review is perfect, but a viral video with an obvious agenda doesn't do it for me.
- tux1968 12y ago
  Heh, fair enough to be sure. However the video and the associated article that I linked do in fact reference multiple official studies. Examples: - http://www.fhwa.dot.gov/publications/research/safety/97084/97084.pdf http://www.fhwa.dot.gov/publications/research/safety/97084/9... - http://www.th.gov.bc.ca/publications/eng_publications/speed_review/Speed_Review_Report.pdf http://www.th.gov.bc.ca/publications/eng_publications/speed_...
  - 12y ago

timbre 12y ago

The Priceonomics article's main point is that raising speed limits doesn't (much) raise actual speed, so it's not inconsistent with papers (like the one you linked) that show that increased speed causes more and worse accidents.

peatmoss 12y ago
As I said, to the extent that the article made the case for combining speed limits with roadway design, I agree. However, the quote from the Lieutenant was clearly stating that speeding was not the problem. The whole article appears to have been either crafted or embarrassingly not crafted to muddle these two questions.
cpncrunch 12y ago
Other research shows that raising speed limits increases accidents, and reducing speed limits reduces accidents. https://en.wikipedia.org/wiki/Speed_limit#Effectiveness https://en.wikipedia.org/wiki/Speed_limit#Effectiveness
- aetherson 12y ago
  Obviously it's hard to judge studies by one sentence summaries, but some of those papers sound like extraordinary claims. "Speeds declined by 5 km/h. Fatal crashes declined by 12%." Come on, really? We're going to imagine that a 3mph change in speed (at speeds around 80mph) could possibly be causal to a 12% change in fatalities?
  - cpncrunch 12y ago
    I haven't looked at the refs, but you're welcome to. I suspect wikipedia is more reliable than priceonomics.com, although you have to look at the sources yourself to be sure.

clairity 12y ago

speed definitely increases the severity of crashes, but i'm not convinced that it increases frequency. even so, the #1 factor leading to increased frequency of crashes is distracted driving (sorry, don't have time to look up relevant links). if it exists, the correlation of accidents with speed is likely much weaker than with distractedness. if we really wanted to reduce motoring accidents, rather than regulating speed, we'd regulate away everything you can do in a car other than drive (radio, food, shaving, makeup, newspapers, etc.). i'd even suggest that driving fast might cause you to be less distracted because of the higher severity of a crash (would be an interesting research topic).

Theodores 12y ago
Maybe we should go back to Cadillac Eldorado 'bullet' style steering wheels (and no seatbelts) which really were as much use as a spike in the middle of a steering wheel.
- seanflyon 12y ago
  It would reduce the number of crashes. Its essentially the same argument as your comment's grandparent, that we should make the roads narrower to reduce driving speed.
tbrownaw 12y ago
i'd even suggest that driving fast might cause you to be less distracted because of the higher severity of a crash And because faster reaction times require you to stay more aware. Unfortunately, trying to find where I heard about this just comes back with a bunch of stuff about risk tolerance w.r.t. financial investments.

reitanqild 12y ago

Mentioned this in another thread and I'm still looking for researh around this topic: A Dutch engineer once told me (back before 2004 I guess ) that they once raised the speed limit on the roads in Netherlands and found that counterintuitively, - average speed decreased. His explanation IIRC was that 1. once people break the rules it doesn't matter how much and 2. when speed limits felt more correct more people respected them. this, according to him, meant that even if some people were driving faster a lot of those who used to break the rules now followed them. I'd still love to know if anyone has any more pointers to research on this and I am fairly sure someone around here knows a whole lot. ( I got some unexpected input in the other thread already.)

peatmoss 12y ago
Interesting! Of course the Dutch are also leaders in highly designed shared streets that make the hippest of the hipster urban designers in the US swoon with envy. Unless we're talking about major highway facilities (and perhaps not even then), my hunch is that we're looking at some radically different street design.
gaius 12y ago
Let's not forget that the speed limit was never about safety. It was about saving fuel in an oil crisis.
- dragonwriter 12y ago
  > 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 in many jurisdictions in the early-mid 1970s (including the US national maximum highway speed limit of 55mph) were due to the concerns of saving fuel in an oil crisis, but that is not true of speed limits more generally (either before -- stretching back to more than a century before automobiles existed -- or after the 1970s.)

ameister14 12y ago

I think it's pretty interesting that you advocate for narrower roads and short setbacks because you belive that on roads like this people are less likely to speed. I don't know if people are less likely to speed on those roads; I think it is unlikely because growing up in a small town, people speed on backwoods roads all the time. Still, I'm not sure that this is the case. What I do know is that roads like that are less safe, particularly if you DO speed. So, unless you can show me that making a road less safe for speeding reduces the rate at which people drive, I'm going to keep thinking that that argument is like saying you can't give out condoms to kids because it makes them more likely to have sex.

TeMPOraL 12y ago
Risk compensating behaviour[0] is a real thing; the question is whether that effect is significant in any particular case. Making the roads look less safe will make people drive more carefully, but it has to be shown whether this will cause a net decrease of actual crash rate. [0] - http://en.wikipedia.org/wiki/Risk_compensation http://en.wikipedia.org/wiki/Risk_compensation
- AnthonyMouse 12y ago
  > Making the roads look less safe will make people drive more carefully, but it has to be shown whether this will cause a net decrease of actual crash rate. There is also the matter that many of the ways to make roads look less safe would in actual fact make the roads less safe. At a given speed, narrower lanes increase the probability of a collision. Parked cars on the side of a road increase the probability that one will be hit, or conceal from motorists the presence of pedestrians about to step into the street. People focused on speed are asking the wrong question. The question is not "how do we get people to slow down" but rather "how do we make the roads safer"? Speed is only one variable.
enf 12y ago
Most of the recent research on factors affecting vehicle speeds is summarized in http://onlinepubs.trb.org/onlinepubs/circulars/ec151.pdf http://onlinepubs.trb.org/onlinepubs/circulars/ec151.pdf In it, Dimauita et al credit every foot of lane width with a 2 mph increase in vehicle speeds, and Wang et al credit each additional lane with a 6.5 mph increase.

autokad 12y ago

the article repeatedly mentioned: raising speed limits does not raise driving speeds on roads. humans are kind of strange in the fact that they drive at a speed they are comfortable with. also, while that (faster = crash more) may be true, its not the only thing going on. it may be the case (and one argued in the article) that driving speed differences results in more crashes.

bryanlarsen 12y ago
"raising speed limits does not raise driving speeds on roads" I suspect that's a temporary effect. The speed people are comfortable at is mostly a learned phenomenon. The more they drive fast safely, the more comfortable they feel. Remember when you first started riding your bicycle? 10 mph was super fast and was super scary. And it is; that's faster than the speeds that the human body was evolved to support.
- autokad 12y ago
  i didnt keep riding bicycle faster and faster and faster. i got to a point where i was comfortable at that speed...
  - wiredfool 12y ago
    Alternate explanation: You got a point where it's physically very hard to go faster. Most people who ride motorcycles or mopeds do it faster than they would on a bicycle.
    - jdbernard 12y ago
      And yet, as someone who travels almost exclusively by motorcycle, there is a limit to how fast I am willing to go which varies depending on the road I am on. My bike will easily go much faster, and I feel like I could safely command the bike even going fair bit faster, but I am not comfortable going faster on a regular basis.
      - 12y ago

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Spooky23 12y ago

End of the day, you shouldn't have laws that 80% of the population breaks during the ordinary course if business. I've found myself in vehicles towing trailers where 65 mph was about as fast as I could go. I continuously had cars passing me. If everyone is a criminal, something is wrong with the law.

cpncrunch 12y ago
They say 85% break the limit, but by how much? According to a 2003 UK study only 25% of people break the 30mph speed limit by more than 5mph, and only 20% break motorway speed limits by more than 10mph. https://en.wikipedia.org/wiki/Road_speed_limit_enforcement_in_the_United_Kingdom#Effectiveness https://en.wikipedia.org/wiki/Road_speed_limit_enforcement_i...
- PantaloonFlames 12y ago
  I think you have that backwards. The text in the article was: > they want to set the speed limit so that 15% of drivers exceed it and 85% of drivers drive at or below the speed limit. The citation you provided is roughly consistent with that. The original article also said: > Lt. Megge believes the compliance rate in Michigan to be well under 50%. That's the only part that estimates rates of non-compliance. And it's not 85%.
  - cpncrunch 12y ago
    Actually, the article says “I’ve found that about 10% of drivers truly identify the speed limit sign and drive at or near that limit,”. That is what we were discussing here, not the 85/15 percentile thing. (Sorry I should have said 90% rather than 85%). Of course the article doesn't say what those other 90% are doing. I suspect they aren't all breaking the limit - probably some are going slower than the speed limit.
rtpg 12y ago
Well, there seems to be this myth that its OK to speed 5 miles above the posted speed limit, so the speed limit is still useful. It'll just be limiting the speed to 60 instead of 55. As to whether things are enforced that way, that's a different story.

nilkn 12y ago

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.

quantgenius 12y ago

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.

peatmoss 12y ago
And yet occasionally lets slip quotes like the one I posted earlier, in which the officer sites anecdata that speed isn't the problem. The article I posted was specifically countering that notion. The broader issue I have with this article is its prescription for bringing speeds and speed limits closer together--namely increasing the speed limits. I think using roadway engineering to decrease the speeds is actually addressing the first order problem.
- NoPiece 12y ago
  If you are talking about an urban boulevard, then I agree. Engineer the street to lower speeds, and increase safety because there are pragmatic options (roundabouts, speed bumps, more signals and stop signs. But if you are talking about intercity highways, something like Los Angeles to Phoenix to Denver to Des Moines, then just increase the speed limit.

mrgriscom 12y ago

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.

thrownaway2424 12y ago
I hate slippery-slope arguments, but I feel that if you are going to advocate the scenario you seem to have advocated, then you can take it a lot further. For example I feel that anyone whose car stalls while crossing the San Francisco-Oakland Bay Bridge should be banned from driving for life. Because every time someone stalls on the bridge at rush hour there's a traffic jam clear back to Reno.
rtpg 12y ago
The tradeoff for speeding is stupidly small. Average US worker spends 25 minutes on a one-way trip to work. Lets assume an average speed of 60mph (hint: it's slower). If you went at 70 instead of 60, then you'll save a whole 3.5 minutes. Here(http://webcache.googleusercontent.com/search?q=cache:jWbI1mKY8qgJ:www.nhtsa.gov/people/injury/enforce/speed_forum_presentations/ferguson.pdf+&cd=1&hl=fr&ct=clnk http://webcache.googleusercontent.com/search?q=cache:jWbI1mK...) is a link to a NHTSA presentation on speed limit changes and its effects on crashes. Notably, when states were given control of speed limits, we saw raises from 60-65 to 70-75 mph in some situations, and a 35% increase in fatalities. if we do the whole "life is worth $3M dollars" argument, divide by two because I'm trying to make this favorable to you (even though car fatalities disproportionately affect young people), letting people go 70 instead of 60 could still end up causing almost 10k more deaths per year, so there's $15B in lost value per year. At least I'll get to sleep in for 3.5 more minutes.
- rokhayakebe 12y ago

spott 12y ago

Respectfully, you didn't read the rest of the abstract to the article you cite, and the next few sentences support what the article says: >Other studies looked at speed dispersion and found evidence that this is also an important factor in determining crash rate. Larger differences in speed between vehicles are related to a higher crash rate. Without exception, a vehicle that moved (much) faster than other traffic around it, had a higher crash rate. Which is the whole point of this article. The article isn't saying that isn't dangerous, it is saying that speed differential is more dangerous than speed. It is saying that speed limits are generally ignored by most people (most people drive some combination of the speed of traffic and the speed they feel comfortable with), however the few people that DO listen to them cause accidents because it makes the differential speed much higher. > A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. This is a horrible starting model. The severity of crashes is physics, but the frequency can't be looked at in isolation. Even the article you cite hints at the fact that the relationship isn't that simple: In figure 1, rural roads with higher speed limits have a shallow linear relationship between crashes and speed, while urban roads with lower speed limits have a much steeper, exponential relationship between crashes and speed. Which counteracts a very simple "speed increases the frequency of accidents".

peatmoss 12y ago
Respectfully, I did, and you're failing to acknowledge what I wrote in my initial posting. > it is saying that speed differential is more dangerous than speed. No it's not, the article is saying that a delta in speed is a factor in crash frequency. (And no, I didn't copy paste the whole abstract, because I was posting the part of the abstract germane to the quote I cited from the original article.) > This is a horrible starting model. The severity of crashes is physics, but the frequency can't be looked at in isolation. No, it's still a good starting model. If you read all the way to the end of that abstract, I think you'll see my point: > Without exception, a vehicle that moved (much) faster than other traffic around it, had a higher crash rate. With regard to the rate of a (much) slower moving vehicle, the evidence is inconclusive. So, much faster moving vehicles always had higher crash rates, while much slower vehicles... inconclusive. There's a saying in statistics (George Box) that all models are wrong, but some models are useful. I think you'll find examples where speed isn't a problem, but those aren't the norm. If you're looking for a simple univariate model that goes a good long ways toward explaining vehicle safety, I'd challenge you to come up with a better one than what I've proposed here.

aetherson 12y ago

Let me rephrase what I think your argument is: "I think that we should set speed limits to somewhere around where they are now or lower, and then re-engineer our roads to make it harder for people to speed. This is practical and will save lives, and the evidence supports this." If I'm reading you correctly, I have a number of problems with it: 1. I don't think it's in any way practical to re-engineer roads on the massive scale that would be necessary to do this. If, as asserted, the majority of people exceed the speed limits the majority of the time, you're talking about re-engineering the majority of roads. That's an enormous project compared to resetting the speed limits. 2. You're a bit light on details about what you would do to make people obey the speed limits, but you list as contributing to speeding "wide lanes, big setbacks, and homogenous environments." Leaving aside homogenous environments (are we now talking about re-engineering not only all of our roads, but also all of our cities in general?), I'm sure that making lanes narrower and setbacks smaller would in fact make people drive slower, but would it actually increase safety compared to the counterfactual of not re-engineering and increasing speed limits? I doubt it. Certainly, I don't see evidence for it. 3. Hidden in here is a question of legitimacy. Are current speed limits a result of a social consensus about the speed/safety tradeoff made by an open society? I don't think that there's any convincing evidence that they are. They appear to be a reaction to OPEC and a revenue model for local governments at least as much as they are about a democratic consensus -- and to the extent that they are about a democratic consensus, they seem to be based on one in which the democracy in general was not aware of the deleterious effects of low speed limits in terms of speed differentials. So, look, the situation right now appears to be: a. Roads designed for speed, but with artificially low speed limits leading to inflated danger. And a couple of possible future policies could be: b. Roads designed for speed, with higher speed limits leading to reduced danger compared to a. c. Roads designed for lower speed, with the same or lower speed limits leading to reduced danger compared to either a. or b. It seems like you've jumped to the conclusion that option c is the right one, but I don't know that it is, even granted that it is the safest option.

dwd 12y ago

It also ignores that speed limits are largely determined by what speed would allow you to safely stop if there was an road obstruction (traffic, animal, merging vehicles, etc).

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TheOtherHobbes 12y ago

>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. More than that, it's pure econo-meta - regulation is bad, freedom is good, if you leave people alone they'll behave responsibly, and everyone wins. It's a moral parable (for economic values of 'moral') not a peer-reviewed paper. Here's a newspaper piece that summarises some of the relevant peer reviewed research and draws a different conclusion: http://www.theguardian.com/news/datablog/2013/may/13/speed-limits-reduce-number-road-deaths http://www.theguardian.com/news/datablog/2013/may/13/speed-l...

rrss1122 12y ago

I would not trust the average person with higher speed limits. If they want to be adequate, safe, reasonable drivers, then they should drive at a slower speed and get used to it. I get the feeling that the reason most people who speed do it is because they overestimate the amount of time they'll have to get to where they're going and speed up when they see they're gonna be late.

matdrewin 12y ago

You obviously didn't understand the article. It didn't say that speed wasn't dangerous. It said that speed signs only give us the illusion of safety because the majority of people disregard them anyways.