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/S0001457505...

Priceonomics's banner ad tells me it is selling a new book titled "Everything is Bullshit." Quite right.

>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".

It's just an abstract that we're discussing here, I know, but the abstract absolutely, categorically does not say that. At all. You're guessing that's what it means.

> 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.

There was little evidence presented that justified the assumption that most people won't drive any faster with a raised speed limit, but if we take that as true, then its conclusion is consistent with the research you linked. It is NOT making the claim that driving faster is safer. In fact, it again clearly states that in an ideal world, everybody would just travel at slower and safer speeds, but that we can't effectively enforce such a low speed limit.

Emphasis mine. Your slower moving vehicle could relate to vehicles moving slower than other cars. Which is what gp claimed.

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.

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.)

The data is open and there is a nice website showing the top speeds: http://www.bestwelsnel.nl/ (best wel snel = pretty fast)

Is there any documented effect of that data being public to people trying to "beat" the speeds?

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.)

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.

Actually saving fuel would have involved sitting down a dozen auto manufacturers and persuasively asking them to participate in a cartel to improve vehicle fuel efficiency without disproportionately harming any individual participant's competitiveness.

Instead, they ordered 250 million people to slow down. According to the article, only 10% are generally willing to do that consistently, and that just increases the collision rate.

So in the end, the 55 mile per hour speed limit wasn't about anything but ignorant management doing something with a high visibility to appear wise, leaderly, and decisive. But it actually just hurt everyone else. We've seen that story so many times, the details are practically unnecessary.

The sad thing is that the people that really need to learn the lessons of history are too busy trying to crank out more illustrative examples.

Maybe European cars are different?

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.

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: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.

3.5 minutes/trip saved * 2 trips/day * 200 working days per year (probably more) = 1400 minutes saved per year per person.

working-age population of US (2012) = 243 million. Employment-to-population_ratio = 67%, so 162 million.

Let's say that half drive, or 80 million. So, 80m * 1400 minutes = 112 billion minutes a year saved by speeding or 1.9 billion hours. At a wage of $10 per hour, that's $19 billion, which is a bit ahead of the $15b loss of value per your number, but I'm sure our confidence intervals overlap.

112 billion minutes = 213000 person-years of being stuck inside a car saved by speeding. With a US average lifespan of 79, that's 2700 total additional lifespans spent in a car by losing those 3.5 minutes.

Come on, that's not a fair argument. The effects are obviously much bigger than one guy saving 3.5 minutes.

To get closer to the meat: If your calculation always outputs numbers that make slower traffic look better, no matter what the starting speed is, then your methodology is wrong. Your method here would make 15mph look better than speeds 20mph or faster, despite a 15mph speed limit being a blatantly terrible idea.

(Also doesn't your assumption of an average speed of 60 bias your argument heavily against high speed limits? I would expect saving 4 minutes on a 30mph route to be much safer than saving 4 minutes off a 60mph route. Is my expectation wrong here?)

Obviously if we're going from 15 to 20 the numbers change. But at the same time if people were on average driving around at 15mph on average car accidents wouldn't be such a big issue, instead of the leading cause of death among teenagers.

actually with lower speed limits you would gain more time by going 10mph faster. For example, if people were driving at 10mph on average, going 20mph would half their transit time. The point is that the speeding people commit usually doesn't earn them much more time, but disproportionately endanger themselves and those around them at higher speeds.

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.

As to whether things are enforced that way, that's a different story.

I don't think skirting the limits has much impact on behavior as the limits go up. In my personal observation, I've observed little if any difference between highway driving on the Deegan Expressway in NYC (50 mph), i95 in South Carolina (70/75) or the mass pike (65). Once you hit 70-80 mph, driving requires more attention.

On the other side, you have absurd local limits as well. The standard for streets in most towns in New York was 35 twenty years ago. Now it's 30, with zones as low as 15 or 20 mph near schools. It's a scheme to get bigger tickets and more drug arrests in "school zones". I wish they'd just get to the point and put up a toll barricade.

That seemed like a pretty good reason to have lower speed limits in pedestrian areas to me.

The goal of improving roads is to increase the throughput of traffic. If it seems as though a problem could be solved by slowing down traffic, that's like solving a problem with a circuit by throwing a resistor into it. It may solve the immediate problem, but it will also reduce the overall efficiency of the circuit by converting energy into heat rather than usable work.

They could also put up signs that say 100% of the people who drive 40 mph reach their destinations 33% faster than those who drive 30 mph. It's just a distraction from the fact that solving the problem in a better way is more expensive than just blaming drivers and letting insurance handle the fallout.

"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.

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.

So maybe those signs are on streets where throughput is not the primary goal, and where substantial barriers would interfere with people moving from their parked cars to the sidewalk and the like.

If you look at a high-traffic street where parking is prohibited, the Magnificent Mile in Chicago, you'll notice that there are gigantic concrete planters between the cars and the regular pedestrian traffic. Retail stores protect their entrances with concrete bollards. Construction zones protect workers from traffic with segmented Jersey barriers and water-filled crash barrels. Those are actual solutions.

But then you have suburban pearl-clutchers who lobby for a 15 mph speed limit and speed bumps in their cookie-cutter subdivisions, rather than actually making their streets safer for pedestrians. Or by replacing yield signs with stop signs. Those people don't realize that "change the law" is not always equivalent to "fix the problem".

> 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%.

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.

https://en.wikipedia.org/wiki/Speed_limit#Effectiveness

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.

[1] http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vanco...

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.

Examples:

- http://www.fhwa.dot.gov/publications/research/safety/97084/9...

- http://www.th.gov.bc.ca/publications/eng_publications/speed_...

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 close to pure physics you'll find in transportation engineering):

From the FHWA's report:

These requests are founded on public knowledge that crash severity increases with increasing vehicle speed, because in a collision, the amount of kinetic energy dissipated is proportional to the square of the velocity. Simply stated, when a vehicle is involved in a crash, the higher the vehicle speed, the greater the chance of being seriously injured or killed.

and quoted by the BC report:

A driver’s choice of speed can impose risks on other road users. Crash severity increases with increasing speeds because in a collision, the amount of kinetic energy dissipated is proportional to the square of the velocity.

Now, beyond this, there are some subtleties. Both of these reports state that crashes are more likely to occur when there is a greater delta between fast and slow roadway users. That's fine. They also talk about how speed limits are more likely to be exceeded where the roadway design encourages higher speeds. Emphatically agree.

So, now we are left with a policy question. Surely we agree that habituating people to breaking the law is bad. 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?

Normatively, for most roadways (especially those containing bicycles and pedestrians), I say we need to move more toward changing the roadway design to discourage higher speeds. On some highways, it might be appropriate to lift speed limits, though even then I'd tend to cast a cautionary gaze toward the Montana experiment that was referenced elsewhere in this thread.

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, so changing the design to reduce the incentive for high speed may not improve safety as much as the reduced "natural speed" would seem to suggest -- and may retain the high delta beteween fast drivers and slow drivers that you note is a major factor in accidents, just reducing the median.

But what if through technology we could get enforcement of existing limits to a place where the probability of penalty for violations was higher (even if the penalty range had a lower bottom end)? One problem with law as an factor in behavior right now is that the probability of any given violation (or even a pattern of consistent violations) being punished is so low that the law serves more as a very weak social signal and the source of an inverted lottery of punishment than as a rational utility factor in regular behavior calculations.

With more consistent enforcement, we may be able to reduce the delta between high and low speed drivers (as the high speed end is usually significantly above the legal limit) without changing the law (at least, the speed limits in the law) or the road design significantly.

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.

But this is going to be a hard sell for both drivers (who feel entitled to their high speed) and law enforcement (which treats ticketing as a revenue source; widespread deployment of such system would dry up the money stream almost immediately).

It wouldn't be a tough sell to lower speed limits on some portions, and raise it on others, even on a time-neutral but safety-positive basis, but yet, the powers that be stick to their arbitrary number.

I haven't seen any actual calculations used for setting speed limits, but I do remember being taught in school (on physics lessons) that if you want maximum road throughput then after factoring in safe distance (which is proportional to square of velocity) you end up with ~50km/h as a sweet spot. Even if some other factors (like fuel efficiency) alter this calculation, 100km/h feels quite plausible to me.

Also I believe that many consider speed limits as arbitrary because most people seem not to care about safe distances anyway.

Ultimately, how many deaths are acceptable for people to get to work 5 minutes earlier?

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.

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.

Most people who ride motorcycles or mopeds do it faster than they would on a bicycle.

Just like on a bike, the first one was a heavy steel one with thick tires. Now, I'm riding a road bike that weighs a tiny amount and has dual compound tires.

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-l...

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.

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.

[0] - http://en.wikipedia.org/wiki/Risk_compensation

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.

"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.

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).

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.

There is very little crowding on the stretches of highway I'm most familiar with. If the speed limit was 120, I'd probably cruise around 90 or so, assuming it wasn't rush hour. I propose that there is a diminishing impulse for travel rates as they increase, but also that on well-cleared, divided, limited-access highways, we have diminishing utility for speed limits as a regulating concept. Highway driving is the easiest driving to do. There are more variables in control than anywhere else. Why not re-evaluate the roads, not based on the 85th percentile of drivers living under the threat of litigation based on arbitrary bureaucrats, but on simple road capacity and volume?

Starting a couple of years ago, Virginia started bumping up the speed limit on the more rural sections of interstates from 65 to 70MPH. Part of the stated rationale was that a lot of people speed anyway, but a lot of other people drive the speed limit, and this disparity is dangerous. By bumping up the limit, you're in essence telling the law-abiding drivers "it's OK to keep up with traffic" and the gap in speeds will narrow.

In my experience, the opposite happened. It seems that the people who were driving 65 before don't want to go any faster. The people who were speeding before still constrained their speed to some factor above the speed limit, and now they go even faster still. Previously, the spread was around 65-75, now it's more like 65-80.

In contrast, the interstates around DC are all limited to 55, yet people regularly do 70 there as well.

It seems clear to me that, while speed limits don't impose an iron control on vehicle speeds, they do influence it.

A sibling poster mentions studies that say it changes little if at all. Perhaps what's "clear" to me isn't true. However, I wonder just how those studies were performed. How long did they wait after the changed limit to measure the change in speed? Most traffic on most roads consists of people who make the trip regularly, and it will take time for them to change their habits, up or down.

“Over the years, I’ve done many follow up studies after we raise or lower a speed limit,” Megge tells us. “Almost every time, the 85th percentile speed doesn’t change, or if it does, it’s by about 2 or 3 mph.”

The article seems to quietly conflate the fastest 15% of drivers ignoring the limit with "most drivers" ignoring the limit. Which is odd. However, even under the _archon_ model, increasing the limit would lead to a reduction in speed variance.

For a long time in Nevada there were no speed limits (prior to the 55 law) and we'd drive up 395 toward Reno at 80 - 85 mph which was just fine.

It seems like you just have to believe that making a faster limit won't ratchet people to 'limit + 15' where they are when it is 65.

Just as Megge can point to the results on hundreds or thousands of roads which have become more safe or equally safe when the speed limit increased, other researchers looking at data sets of speed limit changes have come to the opposite conclusion and advise that raising speed limits comes with the price of thousands of roadway fatalities.

Although the article seems to support Megge and the studies he likes, it's not clear why (other than maybe that it makes for a more interesting blog post).

And honestly, I can't imagine I'm the only one who feels comfortable going 80 on a 65 MPH highway but not on a 55 MPH highway. I guess it is possible, but it seems hard to believe.

And, sure enough, any ticket I've ever gotten is because I was going over 10mph faster than the speed limit.

Depends on your cops.

I've witnessed tickets for 5 over (40 in a 45), 4 over (49 in a 45) and a stop, thankfully without a ticket for 1 over (31 in 30).

I'm given to thinking of it as a lottery. Someone is getting pulled over, today me, tomorrow someone else. I'm just glad I haven't had a case of 'marijuana smell' for 10 years or so.

Performing a bad action does not cause someone to forfeit all arguments as to fairness.

One interesting thing I observed while driving to university was that there was this one section of highway that was marked at 60km/h, but everybody drove around 95km/h. Every now and then there would be a cop that would give out a bunch of tickets, but it didn't seem to change the speed people went.

Well it turned out that the person that ordered the sign had a dyslexic moment, and the speed limit was later changed to 90km/h. What was interesting was that the design of highway (the guards, the lane width, the shoulder, the banking of the ramps) were all cues for drivers and they drove the actual intended speed without regard to the maximum speed sign.

I think that's neat.

Also, the State Police in my state, PA, typically won't pull you over on a highway marked 55mph unless you're doing over 80mph, so what does that tell you?

In France, that's how the law works: http://www.americansinfrance.net/images/Driving_School/Road_...

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

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 there are narrow curves, unclear conditions etc. In my experience, this system works wonderfully: when the road is good, you can drive as fast as you like, so people are more concious about paying attention to the road and their rear mirrors, especially when hogging up the left lane.

I acknowledge that completely overtaking this system would be impossible for the US, simply because the roads are not up to it and the driving tests are not rigorous enough, but I think Germany serves as a fine example that there would be no harm in raising the speed limits a few notches.

Your theory sounds all nice and works if you drive on empty roads, but as soon as there's a bit of traffic the lack of a speed limit results in a very stressful and uncomfortable driving.

The main problem is the speed difference between the individual lanes. On the right lane you have the trucks which are limited to 90 km/h by law, so that's the maximum speed you can usually drive on that lane. Now most highways only have two or three lanes. No speed limit usually results in a difference of at least 40 km/h between lanes and always-changing speeds because of traffic. Driving in a small car with a low-power engine is no fun at all, your only choices are getting stuck behind trucks at 90 km/h or a constant speeding up, slowing down, switching lanes and pushing your car to its limit.

My personal theory is that this is one of the main reasons why German drivers are so aggressive. The drivers most in favor of no speed limit are usually also the most aggressive.

AS a person who drives through Germany frequently I am yet to see an aggressive driver on the Autobahn.

My point? Anecdotes don't prove anything. One person says that Germans are aggressive, another says they aren't. We need hard data instead.

Result -- zone out on cruise control, look at your phone, talk to others in the car, etc. Focus on the road? Nope.

I fully support 50kmh urban street limits, but the open road sections should have a day/night limit, where the day limit is 130, like most of Europe and some parts of the US. There should also be limits to how often a speed limit can change in a single stretch of road, and highway speed zone changes should have a minimum of three signs at even spacing to indicate the change approaching, at the spot and one more reminder.

There should also be a ban on concealed traffic cameras - getting a fine long after the event has very little effect on the behaviour, apart from generating feelings of injustice.

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.

Peugeot Partner 2.0 HDi - 6-7l/100km when driving in city traffic, 12-13l/100km when driving at 140km/h,

Land Rover Discovery 3 4.4L V8 - 15-16l/100km when driving in city traffic, 9-10l/100km when driving at 140km/h.

Basically your engine should stay below 3000rpm - if you have to keep it at 4000rpm just to maintain a certain speed then it's too much for the engine and it's not being efficient.

(US citizen here - I don't know about German drivers, but of course the skills of Germans are legendary. The automotive media tells us all German drivers are as skilled as Walter Röhrl. I'm only partially kidding.)

Driving is not a right and it should not be treated that way.

The skills here are not legendary per se; the mean might be a bit better. The difference is that people seem to have more respect for other drivers and dangers on the road, creating more awareness overall.

But still, I think allowing skilled drivers to drive faster would do no harm to the population, if the faster people stick to the guidelines. For example: you do see the occasional snail moving in the left highway lane, but it won't be long until he is ushered away by some faster car with some furious flashes of the brights.

the initial steps to obtain a driver's license are much harder than in the US, that's correct.

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 the third highest fatality rate in the nation [3]). It's a good guess that traffic volume has gone up, but safety technology has improved as well, so there are a number of variables that have to be accounted for. The differences are certainly stark enough that it merits some consideration, though.

Nationwide, traffic fatality rates have been on a steady downward march over the last couple of decades [4], so Montana's tremendous leap in fatalities is absolutely anomalous. If I was debugging it, I'd start looking at what changed around that time. On the face, it certainly looks like posting and enforcing speed limits made the roads less safe, though.

[1] http://www.hwysafety.com/hwy_montana.htm

[2] http://www.mdt.mt.gov/publications/docs/brochures/safety/hsp...

[3] http://missoulian.com/news/local/report-montana-highway-deat...

[4] http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in...

  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)

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.

  http://www.nhtsa.gov/FARS
  Select tab "Run a Query Using the FARS Web-Based Encyclopaedia"
  "Query Fars DATA" which takes you to 
  http://www-fars.nhtsa.dot.gov//QueryTool/QuerySection/SelectYear.aspx
  For each year 1998,1999,2000
    Select Query Year, e.g. 2000, then Submit
    In the top section Tick 
     “Roadway Function Class” 
     and “Month”, then Submit
    Select State: Montanta, and RFC Roadway Function 
    Class “Rural-Principal Arterial-Interstate”
    Select Univariate Tabulation
    Select Variable - Crash Month and “Show Zeros” Yes

  1998-4,0,2,4,5,1,5,4,0,0,3,2,30
  1999-1,1,3,2,1,0,2,9,4,2,1,4,30
  2000-2,1,3,5,1,5,3,3,3,1,4,4,35

- 65 Mph

- "Reasonable and prudent" daytime speed

- 75 Mph daytime speed

During the reasonable and prudent period, I think many people still had an internal model of 65 Mph. Certainly many people did drive faster. In my younger days, friends and I would find straight, empty sections of highway to flirt with death. But... many many people still set their cruise control to 65.

Case in point, my parents and the parents of many of my friends were careful to clarify that "reasonable and prudent means 65 mph, or you will have your driving privileges revoked." I was out from under the parents' roof by the time things went to 75, but I know my own highway averages went up with the codification of 75 mph.

Do you have any other insights into other factors that might have contributed to the change in fatalities, or do you think it was just as simple as "people are driving 10 MPH faster on average", with correlated increases in fatality rates?

- R&P: people look at the road

- 75 : people look for cops (if they're above speed limit)

I'd bet that among the 65-ers, it probably did map pretty well--or at least approximately as well as it did in states that retained a 65mph speed limit. You might have seen a few people creep up maybe instead of setting your cruise to 72 mph, in hopes of skirting a ticket, you set it to 75 because... round number?

The daredevils are pretty much by definition going to be exceeding the speed limit, but they could arguably be described as a different group, i.e. one that didn't internalize the 65 mph. A common narrative amongst Montanans of the time was that out-of-state types (most likely Californians, horror!) were coming to MT to treat our roads like a raceway. I'm sure that probably did happen to some extent, though who knows if it was actually a common occurrence.

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.

There's also the "They aren't serious about it" effect. Warning signs should be reserved for locations where it really would be dangerous to exceed a certain speed, either because there's an intersection just after the crest of a hill, or a reverse-banked curve, etc. So people have been trained to ignore the warnings because they're so familiar and have proven (most of the time!) to be not all that important.

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.

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-re...

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.

In my experience, driving on US freeways requires less lane changes than on German autobahns. This is mostly due to the facts that in the US everybody is driving about the same speed; in Germany, as mentioned above, if you want to drive faster than the trucks but not fast enough to stay always left, you are constantly switching lanes to overtake people in the second lane. If you want to drive a speed that is lower than the 'general' second lane speed, you even need to go in and out from the truck-lane.

Furthermore, since it is OK to overtake on the right in the US you don't need to change lanes if your lane now goes a little faster than the lane on the left. Even though you shouldn't stay left for a prolonged time if you are [much] slower than the rest (even in the US), it is OK to be overtaken on the right.

Though, I am faster on German freeways (driving around 160-170km/h), I enjoy driving in the US more as it is generally more relaxed.

I somewhat doubt that the German autobahn rules are better with dealing with medium-high-traffic situations than US rules. Would be interesting to see actual data on this claim.

  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	7.7
  United States of America	7.6
  Slovenia	7.6
  Austria	6.9
  France	6.3
  Canada	6.1
  Switzerland	5.6
  Israel	5.2
  Australia	5.2
  Germany	4.9
  Netherlands	4.9
  Malta	4.9
  Finland	4.7
  United Kingdom	4.3
  Iceland	3.8
  Sweden	3.7
  Ireland	3.4
  Denmark	3.4
  Norway	3.3

I live in Brasil, which, unsurprisingly ranks pretty high as well. Bad roads and unsafe vehicles explain part of the problem; but what I think accounts for the gist of it is something I haven't seen commented here: people speed because they want to be faster than other people. The speed limit merely makes this easier by limiting risk averse or society minded people.

I stoped driving long distances a year ago because it was stressing me out and because a car here is too expensive (compared to bus for long distances and taxi for short ones).

What I noticed in myself and in drivers around me was that traffic was regarded as a competition. Being faster was better. If someone was faster than you you'd be passive-aggressive towards him/her (mostly him). Brasil ranks 2nd (to last) on this list because of the way we view cars: they are really expensive, even in an expensive country such as ours. They are regarded as a life milestone, one of the main goal in our lives. They become a way of posing yourself as superior to the masses. This results in a more competitive traffic. Closing people off, tailgating and speeding (50% more than the limit - above this you risk losing your license and get fined for about $500) are the bread and butter of a good sum of our drivers. Our national speed limit is 120kmph (75mph).

Why do most people speed slightly? Is it because of the time they will save? I bet most don't even look at their watches while doing so. For a fixed distance, the speed x time is a hyperbole, which means diminishing returns for greater speeds for distances greater than the value of your speed. I posit that the gain is not time, but a better position at an acceptable risk in a competitive game we call transit.

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.

source: I have been driving in both countries for more than 8 years; moved to the US little more than 8 years ago.

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.)

(Aside, I agree 100% about more rigorous licensing. I spend 3 hrs on the highway each day; easily 80% of the drivers I see are utterly incompetent: texting, driving slow in the left lane, passing on the right, lights off at night, falling asleep, etc. Heck, I saw one driver eating out of a bowl with both hands.)

Is this two problems or one?

- 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.

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.

This is when driving on highways and major roads, at least.

I vividly remember the days of 55 MPH speed limits in the US, and it was pretty much the same then (a hair under 10 over was the optimal speed, but 10 over was a lower speed back then).

Anecdotal experience and all, but at least for me and other drivers that I've observed or talked to about it, just because people tend to go over the limit doesn't mean that the limit has no effect.

This is all fine by me. I only mention it because this is exactly the kind of topic overly logical people (and/or inexperienced drivers) tend to get bent out of shape about. Just because the speed limit isn't strictly enforced doesn't mean it's useless, and just because a cop could theoretically take advantage of people's behavior and give a bunch of tickets to people for going 5 over doesn't mean that it's a conspiracy by the police.

Wide lanes, one-way streets, and cleaned-up sides without obstacles encourage driving faster while narrower passes and trees/bushes on the side make you naturally slow down. On a road or street well designed you would drive at the limit even if you didn't know what the limit is because the limit is set to the "natural" speed of the road. This is what I believe is behind the sergeant's thinking.

On residential streets, a very narrow design would be the first thing to do in order to slow down automotive traffic and make the street more pleasant and safe for pedestrians. There are streets where it's nearly impossible to drive faster than 10 mph, so there are really no practical limits for speed governance in road design.

Conversely, on highways even astonishingly high speeds can be reasonably safe such as on German autobahns. Highways are mostly protected against the worst accidents such as head-on-head collisions. Things usually go wrong when someone disrupts the traffic flow by unattentive, blind lane changes. This is a completely different safety assessment than what's in effect on the streets of populated areas.

This makes it more difficult for all the (often frustrated) drivers behind to pass the slow car when the time comes, often meaning they put on the afterburners and exceed the speed limit to overtake - which could lead to more accidents, especially if they are trying to squeeze past at the end of the overtaking section, if it is quite short, or there are many cars stuck behind as 'prisoners'.

I agree that there is room for debate on speed limits under ideal conditions on well-maintained roads with bridges that have not been left to rot for decades.

Anyone who has driven internationally will recognize that Americans turn into homicidal/suicidal maniacs when conditions deteriorate--all because they don't understand that the speed limit only applies in ideal conditions.

Driving on U.S. roads in bad weather is a horror show.

I never thought about it that way, and I agree. Speed limit should DEFINITELY be dynamic depending on weather conditions, location, time, traffic etc...

http://en.wikipedia.org/wiki/Speed_limits_in_France

Actual policemen with a camera are rather rare - considering how much road we have - and they get reported to radio stations. Though they're not allowed to tell listeners where they are exactly, only which road they're on.

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.

A driver looking out for cops is a distracted driver. You shouldn't be worried if you are following traffic and going at a reasonable speed. That's not the case at the moment.

"So if drivers disregard speed limits, why bother trying to set the “right” speed limit at all?"

Then let us know what you think.

I'd love to know what the best speed to drive at is, rather than having the posted speed limit be the speed at which no one drives except when the police are around.

Getting bad drivers killed along with several other innocent people is not an acceptable way to solve the problem of road safety.

Let's just focus on getting self-driving cars out the door as quickly as possible.

Many roadways in the US were engineered under a set of assumptions that are incongruous with modern empirical understanding and with modern values. Wide roadways with big turning radii were thought to be safer. Turns out that encourages behaviors that are less safe for a multitude of roadway users. Similarly, there was a 20th century modernist notion that we should use the car for everything. Our bodies (everything from stress measured by cortisol levels, to obesity, to heart disease) object.

The 21st century task of planners is to figure out how to retrofit a system built around monoculture into a system that can accommodate a larger aggregate number of people. Part of that is traffic calming.

Perhaps the police will just go the other way and have a fleet of drones enforce compliance.

I have a friend who got his last point going 65 in that area. He pays $7000 a year in car insurance because of his points.

So, I'd rather they raise the speed limit to 65 (so people got 65-70) rather than keep it at 50 which almost everyone but a few (me) ignore.

The two are sometimes, but not always, linked.

We should stop focusing on policing speed and start policing bad driving.