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Is Every Speed Limit Too Low?

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Re: Is Every Speed Limit Too Low?

#111

Post by softgrow »

cheald wrote: post #38

The data from Montana always struck me as interesting. It's not an awful lot of data presented in this report [1], but there was a substantial increase in traffic fatalities when Montana shifted from "Reasonable and Prudent" speed limits to posted-and-enforced speed limits. I then found this report [2] which indicates that yearly fatalities are approximately double of what they were in the late 90s (and is now around…

Dear readers, the Montana Speed Limit paradox is made up by an advocacy group with a barrow to push. Remember folks, trust but always verify. To quote from http://en.wikipedia.org/wiki/Talk:Speed_limit#Montana commenting on http://www.hwysafety.com/hwy_montana_2001.htm

  The source looks somewhat unreliable and biased. I looked up FARS data for 
  1998,1999,2000 for number of fatal-crashes in Montana (state), for (nhtsa)Roadway 
  Functional Classification=Principal Arterial - Interstate and get the following 
  figures for crashes by month:
  1998-4,0,2,4,5,1,5,4,0,0,3,2,30
  1999-2,2,4,2,1,0,2,9,4,2,1,5,34
  2000-2,1,4,5,1,5,3,3,3,1,4,4,36
  However the "study" has
  1998-4,0,2,4,5,1,5,4,0,1,3,2,31
  1999-2,2,4,2,1,0,2,7,4,1,1,4,30
  2000-4,2,8,5,2,7,7,3,4,1,6,7,56
  I've removed the section, it's obviously made up numbers for 2000 for interstates
  to suit an argument, nowhere near fact. There is a reason for the use of reliable 
  sources in Wikipedia and this is a case in point. Alex Sims (talk) 10:13, 25 
  January 2011 (UTC)
See what someone with an authoritative sounding domain name can do!

Re: Is Every Speed Limit Too Low?

#112

Post by vacri »

cylinder wrote: post #54
cfstras wrote: post #44

Disclaimer: I am from Germany. The speeding system we have here seems to make a lot more sense to me: On most highways, there is no speed limit. The only (theoretical) limit is the motor limitation of 155 mph (250 km/h), which can be taken out, but will almost always lead to losing any kind of motor warranty. In practice, there are limiting signs to 75 mph (120 km/h) for passages where the road is not good enough or…

Yes, the main point is that I pay more attention when driving faster on a freeway. One need only take a road trip in Australia to see how ridiculous low speed limits on open roads are. 110 kmh limit with, yes, very strong enforcement in place, in a completely rural area with few cars around, no people, no pedestrians, on a long drive (it's ten hours from Melbourne to Sydney with basically nothing in between). Result…

110 isn't that much different to the US's 75. There is much stronger enforcement though. I spent six weeks driving around the US, multiple hours most days, and I was generally 0-5 mph above the speed limit... but I didn't have to look at the speedo. Came home, and it was painfully obvious just how much of my attention was split watching the speedo like a hawk because people can and do get fined for doing 64 in a 60 zone. And the fines aren't trivial.

Re: Is Every Speed Limit Too Low?

#113

Post by symmetricsaurus »

bryanlarsen wrote: post #82

IIRC, Sweden has had a "zero pedestrian deaths" goal for the last 10 years or so. Part of that policy was road design, but another pillar was the reduction of urban speed limits to 18 mph, and vigorous enforcement of such. The number of accidents did not drop substantially, but what did drop was the severity of the accidents. An accident that would have been a fatality in the past is now a broken leg or two.

Sweden actually has a goal of zero traffic deaths overall. http://www.economist.com/blogs/economist-explains/2014/02/ec...

Re: Is Every Speed Limit Too Low?

#114

Post by peatmoss »

quantgenius wrote: post #106
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 say…

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.

Re: Is Every Speed Limit Too Low?

#115

Post by tzs »

cylinder wrote: post #54
cfstras wrote: post #44

Disclaimer: I am from Germany. The speeding system we have here seems to make a lot more sense to me: On most highways, there is no speed limit. The only (theoretical) limit is the motor limitation of 155 mph (250 km/h), which can be taken out, but will almost always lead to losing any kind of motor warranty. In practice, there are limiting signs to 75 mph (120 km/h) for passages where the road is not good enough or…

Yes, the main point is that I pay more attention when driving faster on a freeway. One need only take a road trip in Australia to see how ridiculous low speed limits on open roads are. 110 kmh limit with, yes, very strong enforcement in place, in a completely rural area with few cars around, no people, no pedestrians, on a long drive (it's ten hours from Melbourne to Sydney with basically nothing in between). Result…

If the limit were higher, wouldn't you still zone out on cruise control, and so on, just at the higher speed?

Re: Is Every Speed Limit Too Low?

#116

Post by snowwrestler »

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…

There are automated speed cameras in the U.S. I know of several in the DC area. They seem to be calibrated a bit over the posted limit, probably to cover themselves for variance in the accuracy.

Cars who know where the cameras are drive whatever speed they want until the immediate vicinity of the camera, where they slow down to just over the posted limit. Then they speed back up again. Drivers who don't know about them either follow the social cues ("hey, everybody else is slowing down"), or get flashed for a ticket.

Re: Is Every Speed Limit Too Low?

#117

Post by spott »

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…

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".

Re: Is Every Speed Limit Too Low?

#118

Post by cheald »

softgrow wrote: post #111
cheald wrote: post #38

The data from Montana always struck me as interesting. It's not an awful lot of data presented in this report [1], but there was a substantial increase in traffic fatalities when Montana shifted from "Reasonable and Prudent" speed limits to posted-and-enforced speed limits. I then found this report [2] which indicates that yearly fatalities are approximately double of what they were in the late 90s (and is now around…

Dear readers, the Montana Speed Limit paradox is made up by an advocacy group with a barrow to push. Remember folks, trust but always verify. To quote from http://en.wikipedia.org/wiki/Talk:Speed_limit#Montana commenting on http://www.hwysafety.com/hwy_montana_2001.htm The source looks somewhat unreliable and biased. I looked up FARS data for 1998,1999,2000 for number of fatal-crashes in Montana (state), for (nhtsa)R…

I was looking for government numbers for those years, but didn't have much luck. Thanks for the FARS keyword - that looks like it should have the datasets I need! I'm going grab and parse them and see if there's an actual difference in the data.

I somewhat doubt the data was made up, but it's possible that the roadway classifications were chosen in such a way that the datasets supported the point.

Re: Is Every Speed Limit Too Low?

#119

Post by chris11 »

mcdougle wrote: post #8
_archon_ wrote: post #4

I found myself disagreeing with the premise that highway speed limits don't influence people's driving speed. I may simply be part of the 15%, but consider the following anecdata: On I-90 in upstate NY, the "speed limit" is 65. I've gone by several state troopers at 70-75 without issue or confrontation. I don't go faster, not because traffic dictates, but I'm concerned about litigious policemen. To put it in Freakono…

You do raise a good point. I know that, when I started driving, my dad taught me a neat trick: drive 8.5 mph over the speed limit, and you'll never get pulled over. That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops. If you go any more than 8.5mph over, though, you might accidentally cross that 10mph mark, and if a cop's around he'll get you. And, sure enough, any ti…

I think it also depends on the area. I did get pulled for 3 or 4 over the speed limit once. I think it was mainly because I was on a military base. Fortunately I did not actually get ticketed.

Re: Is Every Speed Limit Too Low?

#120

Post by selectodude »

pchristensen wrote: post #53
3pt14159 wrote: post #46

I studied Structural Engineering in University, which was under the Civil program, and, at least in Canada, we don't design for what people will go, but for how drivers can handle unexpected conditions, like cars turning out in front of them, a loss of traction due to ice, and visibility at night. I've also seen multiple studies that show that during high visibility / traction days (summer during the daytime) the spe…

When I lived in Lincoln Park, Chicago (a dense urban neighborhood), there were no speed limit signs. I think the speed limit was 25 mph, but between the narrow streets, parked cars, frequent intersections, and lots of pedestrians, I rarely felt comfortable going faster than 20. They could have had 100 mph stop signs all over the place and I still wouldn't have gone faster than 20.

There really aren't any speed limit signs anywhere in Chicago, and people drive a sane speed depending on the street. And it seems to work, too.

http://www.suntimes.com/27575224-761/chicago-among-safest-us...

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