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Is Every Speed Limit Too Low?

priceonomics.com

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Re: Is Every Speed Limit Too Low?

#201

Post by cpncrunch »

aetherson wrote: post #187
cpncrunch wrote: post #129

Earlier quoted context omitted.

Other research shows that raising speed limits increases accidents, and reducing speed limits reduces accidents. https://en.wikipedia.org/wiki/Speed_limit#Effectiveness

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?

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.

Re: Is Every Speed Limit Too Low?

#202

Post by cpncrunch »

PantaloonFlames wrote: post #140
cpncrunch wrote: post #128

Earlier quoted context omitted.

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_i...

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…

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.

Re: Is Every Speed Limit Too Low?

#203

Post by gabriel34 »

akgerber wrote: post #96

There is very little in this article about the interests of anyone not driving— crash severity is due to speed deltas, and pedestrians and cyclists are almost always moving much slower than automobiles. And a self-interested driver won't slow down to keep pedestrians safe, since pretty all of the consequences of a auto-pedestrian crash fall on the pedestrian.

Granted the consequences are almost aways greater for the pedestrian, but running someone over is very detrimental to the driver as well - there might be severe criminal or civil liabilities depending on where the accident takes place, among many other consequences

Re: Is Every Speed Limit Too Low?

#204

Post by wiredfool »

jdbernard wrote: post #164
wiredfool wrote: post #126

Earlier quoted context omitted.

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.

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.

Yes. Motorcycles are like that. Nearly every motorcycle is physically capable of going faster than the rider is comfortable doing. It's very hard to do that on a bicycle, except perhaps for offroad downhill type rides. On my usual road (bicycling) loop, there's one corner where I actually have to control my speed to feel safe, but even there I could probably take it a good 20% faster than I do. (It's a slightly bumpy, banked right turn @ an intersection at the bottom of a steep hill) So, for 15 seconds out of a 1.5 hour ride, I'm limited by something other than muscle power.

Re: Is Every Speed Limit Too Low?

#205

Post by darklajid »

spott wrote: post #117
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 ar…

Hmm..

What about the Autobahn, me passing traffic with a difference in speed of 100km/h at times (it's entirely possible to reach higher values w/ faster cars, reckless driving, unusually slow traffic on the slow lane, like trucks).

I think it can work. Obviously it cannot work without education and experience, but pointing at speed differences as the one stat that leads to chaos and mayhem seems empirically wrong.

Re: Is Every Speed Limit Too Low?

#206

Post by cfstras »

gnur wrote: post #170
cfstras wrote: post #66

Earlier quoted context omitted.

Exactly -- sure, you can still hide behind a truck and go 100 km/h all the time -- but most cars efficiency sweet spot is around 130 km/h, and driving at that speed leads to more dynamic, occasionally passing trucks, etc.

What is an "efficency sweet spot"? When I consistently drive at the speed limit (in the Netherlands, 120km/h) I have to fill up every 4 working days. When I consistently drive 100 km/h I only have to fill up every 5 working days. Takes 20% longer but the tank also lasts 20% longer.

It really depends on the car. I mostly drive rentals, in the range of Ford Fiesta to Opel Astra -- all of them fell in that range.

Re: Is Every Speed Limit Too Low?

#207

Post by tomkarlo »

rtpg wrote: post #148
Spooky23 wrote: post #99

Earlier quoted context omitted.

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.

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.

While it might be socially acceptable, we'd all also agree that going 5 over the posted speed limit is "breaking the law", which is exactly the problem - it's encouraging a societal norm of "kind of" following the law, which is extremely problematic (especially when you consider that enforcement is often not applied evenly.)

Re: Is Every Speed Limit Too Low?

#208

Post by tomkarlo »

logfromblammo wrote: post #197
saalweachter wrote: post #190

Earlier quoted context omitted.

Is the statistic NYC posts a lie? For a few years they've had signs up claiming that 80% of pedestrians hit at 30 mph survive, while 75% of pedestrians hit at 40 mph were killed. That seemed like a pretty good reason to have lower speed limits in pedestrian areas to me.

Seems like it would be a better reason to increase the physical separation between motorized and non-motorized traffic. I'd wager that more pedestrians would survive near 40 mph traffic if there were more energy-absorbing materials between them and the cars. The signs are probably just up to cut down on lawsuits directed toward the city. The goal of improving roads is to increase the throughput of traffic. If it seem…

It's entirely impractical to expect NY to build collision barriers at every spot where pedestrians get near cars within the city. Unless you want to have raised / underground pedestrian crossings everywhere (which have generally not been found to work very well, and are ugly as hell too), the reality is you're going to have traffic and pedestrians intermixed within the city.

"The goal of improving roads is to increase the throughput of traffic" - that is considered an outdated goal by most planners these days. For one thing, if you increase the capacity of roads, you simply encourage more driving, and things end up congested anyway. In many cases urban planners now actively seek to decrease the throughput of traffic on mixed-use streets in urban areas.

Re: Is Every Speed Limit Too Low?

#209

Post by tripzilch »

gaius wrote: post #74
reitanqild wrote: post #67

Earlier quoted context omitted.

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 respe…

Let's not forget that the speed limit was never about safety. It was about saving fuel in an oil crisis.

I found that argument a little bit weird. Most people I hear about the most efficient speed of their car tell me it's around 110 km/h. That's 68 mi/h.

Maybe European cars are different?

Re: Is Every Speed Limit Too Low?

#210

Post by logfromblammo »

tomkarlo wrote: post #208
logfromblammo wrote: post #197

Earlier quoted context omitted.

Seems like it would be a better reason to increase the physical separation between motorized and non-motorized traffic. I'd wager that more pedestrians would survive near 40 mph traffic if there were more energy-absorbing materials between them and the cars. The signs are probably just up to cut down on lawsuits directed toward the city. The goal of improving roads is to increase the throughput of traffic. If it seem…

It's entirely impractical to expect NY to build collision barriers at every spot where pedestrians get near cars within the city. Unless you want to have raised / underground pedestrian crossings everywhere (which have generally not been found to work very well, and are ugly as hell too), the reality is you're going to have traffic and pedestrians intermixed within the city. "The goal of improving roads is to increas…

It is far more impractical to employ live humans to enforce speed limits and jaywalking ordinances in the name of safety. We don't see the solutions that best improve safety because there are many other considerations in play.

As I mentioned before, the urban planners who are adding resistance to the system are not helping the overall efficiency. Intentionally decreasing the capacity of urban infrastructure is almost criminally stupid. It approaches the level of solving an overpopulation problem by conducting a decimation lottery every time the number of people approaches some upper limit.

Some planners are shutting down some roads to increase throughput, by encouraging greater use of more improved roads. Others are altering roads, or installing traffic circles, or adding stop signs and speed bumps, just to make vehicle traffic gratuitously more difficult. Those people are the assholes.

Congestion results from insufficient infrastructure to meet public demand. If your sidewalk is too narrow for the foot traffic, and people get jammed up and spill out onto the street, you cannot solve the problem by making it narrower and throwing caltrops onto it. And that doesn't work with cars on roads, either.

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