
Is Every Speed Limit Too Low? - malchow
http://priceonomics.com/is-every-speed-limit-too-low/
======
peatmoss
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/S0001457505...](http://www.sciencedirect.com/science/article/pii/S0001457505001247)

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

~~~
spott
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
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.

~~~
nyc640
The article isn't claiming that faster speed == safer. It clearly states that
raising the speed limit has little effect on the speed that most people
travel. The only group of people whose driving speed it significantly affects
is the 10% of people who follow the speed limit exactly (who are usually the
slowest drivers). Therefore, by raising the speed limit, a large majority of
drivers will drive at the same speed (no faster), but the slowest drivers will
speed up and the speed differential drops, making the roads safer, as your
linked article agrees with.

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.

------
_archon_
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 Freakonomic terms, I'm going
just slow enough that I won't get caught. If the limit was 10 mph higher, I'd
drive 10 faster, as would everyone who was on the road for more than one exit
(or governed semi tractors).

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?

~~~
colanderman
It's not an arbitrary premise, it's studied:

 _“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.”_

~~~
streptomycin
And it's apparently controversial:

 _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.

~~~
colanderman
The speed limit drops arbitrarily from 65 to 55 from MA-146 to RI-146 at the
state border. Risk of a ticket aside, 80 is fine on either side of that
invisible line (long straight flat highway with trees on either side).

------
3pt14159
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 speed limit can be safely raised to at
least 130km/h for most highways that are 100km/h.

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.

~~~
pchristensen
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.

~~~
selectodude
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...](http://www.suntimes.com/27575224-761/chicago-among-safest-us-cities-
for-pedestrians-study.html)

------
cfstras
_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 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.

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

~~~
cfstras
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.

~~~
gnur
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.

~~~
gambiting
Depends on the car. If you have a tiny engine, then it will use large amounts
of fuel at high speeds. If you have a large engine, it will use less. My
personal experience:

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.

------
cheald
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 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](http://www.hwysafety.com/hwy_montana.htm)

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

[3] [http://missoulian.com/news/local/report-montana-highway-
deat...](http://missoulian.com/news/local/report-montana-highway-death-rate-
rd-highest-in-u-s/article_f0baa0c4-9998-11e3-8d21-001a4bcf887a.html)

[4]
[http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in...](http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in_U.S._by_year)

~~~
softgrow
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](http://en.wikipedia.org/wiki/Talk:Speed_limit#Montana)
commenting on
[http://www.hwysafety.com/hwy_montana_2001.htm](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!

~~~
cheald
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.

~~~
softgrow
No I think the so called paradox was made up, To verify:

    
    
      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
    

Output

    
    
      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
    

Then lose your doubts.

------
bryanlarsen
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.

~~~
symmetricsaurus
Sweden actually has a goal of zero traffic deaths overall.
[http://www.economist.com/blogs/economist-
explains/2014/02/ec...](http://www.economist.com/blogs/economist-
explains/2014/02/economist-explains-16)

------
chiph
There's got to be a term for it, but the factors that influence how fast
people drive on a road include how well it's been maintained, how congested it
is, but also purely visual factors like whether there are trees or signs or
buildings crowding the edges of the roads.

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.

~~~
Gracana
"Traffic calming" is the term used for the stuff you described that causes
drivers to instinctively slow down. Curb extensions at crosswalks and narrow
lanes seem to be the most effective measures, in my personal experience.

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

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

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

------
Symmetry
Their reasoning about the dangers of low speed limits make a lot of sense when
you're looking at highways, but I don't think they'd necessarily apply to city
or residential streets where there are frequent red lights, pedestrians, etc.
Of course, the right thing to do there is probably to configure the roads so
that people drive more slowly naturally by narrowing lanes, having trees on
the side of the road, etc.

~~~
wahsd
It doesn't even make any sense regarding highways. Ignoring their
embarrassingly flawed standard for setting speed limits based on a percentile
of speed limited traffic, there are so many other factors that go into the
danger of traffic that are wholly and totally separate from speed. I would
argue that the speed is exponentially less significant than the skill and
training and experience of the drivers.

Take a 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...](http://en.wikipedia.org/wiki/List_of_countries_by_traffic-
related_death_rate)

~~~
malchow
The data in the Wikipedia article you cite can also be sorted by road
fatalities by 1 billion vehicle/kms. This accounts for variance in population,
auto ownership, and amount of driving.

    
    
      Country and traffic fatalities per 1b veh/kms.
    
      United Arab Emirates 310
      Brazil	55.9
      Slovakia	24.5
      South Korea	22.8
      Bulgaria	19.1
      Estonia	17.5
      Cyprus	16.7
      Czech Republic	15.7
      Malaysia	13.8
      Spain	8.5
      New Zealand	8.3
      Japan	8.3
      Belgium	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
    

As usual, everyone in the Nordics is home counting bullion, so nothing going
on there. But among the more vibrant quarters the U.S. doesn't seem especially
dangerous.

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

This is because:

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

~~~
sbalea
Wow, I was thinking just that. It's the only place i've seen posting a 100km/h
limit on a narrow, barely two lane winding road, hugging a cliff. It was
almost like a dare. The speed I felt safe at was no more than 50 km/h

------
mwfunk
I've lived in the US all my life, with my excessive number of years split
between Michigan, North Carolina, and northern and southern California, and in
all of those places the proper range of speeds was anywhere from the posted
speed limit to a hair under 10 MPH over the posted speed limit (I prefer the
latter :). Go slower than that and you start blocking traffic, go faster than
that and you might get a ticket.

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.

------
yason
I think that the road design is a key factor in how fast people drive, not
limits.

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.

~~~
australis
A similar effect can be noticed on sections of roads with dedicated overtaking
lanes. Cars that are travelling below the speed limit for long stretches of
road (and can't be overtaken due to the road), tend to speed up to the actual
speed limit when an overtaking lane comes along - likely due to the more open
road, they feel safer driving faster, etc.

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'.

------
ackfoo
The problem with speed limits is that people think they are a license to go
that speed, or a little faster, regardless of the conditions. Americans are
nearly universally useless at slowing down for things like ice, heavy rain and
fog. They ignore things like stopping distance and diminished reaction time in
poor visibility.

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.

~~~
rokhayakebe
_The problem with speed limits is that people think they are a license to go
that speed, or a little faster, regardless of the conditions_

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

~~~
greggman
Sounds like an idea for a startup. Electronic Paper Remotely Updating Speed
Limit Signs. Get a government contract to replace all the signs and PROFIT :D

------
saticmotion
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 rotated every once in a while.

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.

~~~
dfxm12
In the US, automated cameras are generally limited to capturing people driving
through red lights, if they are used at all.

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

------
ajmurmann
Having moved to the US from Germany, it always stroked me as particularly
dangerous that it is common to overtake cars on the right and have slow cars
and fast cars in any lane. The article mentions that different speeds are
dangerous. I think enforcing cars sorting themselves properly into the right
lane would make a huge difference in reducing accidents and allowing traffic
to o faster. I wish law enforcement could focus on that instead of giving
tickets to people who go 5mph/h faster than most other cars.

------
lutorm
If there's a state that should win the price for speed limits that make no
sense, it must be Hawaii. We have stretches of straight, extremely wide
highways with no intersections and a speed limit of 40mph. Then you come to an
old, narrow, and curvy road and it's 55mph. Or it could be 35mph. It's like
the speed limit is set by a random number generator.

------
akgerber
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.

~~~
gabriel34
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

------
moneybags4
The lower the speed limit, the easier it is to generate traffic ticket
revenue. It's a money game. In California, they tell you that whatever the
judge tells you your traffic ticket fine is, say $100, your total is 6 times
that when administrative fees are added in.

~~~
greggman
They're more if you add in how much your insurance premiums go up. I believe
it's $300 per year per point so $900 for 1 point since they last 3 year. (at
least it was $300 a year for me for getting 1 point).

------
evjim
I believe low speed limits give police officers a legal means to stereotype
drivers and pull them over. Since everyone is now speeding, they can pick and
choose who to pull over and have a legal reason. Young? sketchy car? minority?

------
DatBear
This article continuously states that speed limit signs have little to no
bearing on how fast people actually drive, and it says Lt. Megge is actually
arguing this. If it has no bearing on how fast people drive, and changing
speed limits actually doesn't affect the speed of traffic like they say in the
article, why are they changing them? Why are they too low right now? Why does
the 85th percentile matter at all? If people pay as little attention to speed
limit signs as is mentioned in the article, wouldn't changing them have no
effect on safety whatsoever - be it lower or higher, better or worse?

~~~
matdrewin
Cops would spend less time issuing useless tickets and concentrate on the real
speeders.

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.

------
djloche
I'm an advocate of getting rid of speed limits completely. Rather than having
speed limit signs, post signs that suggest the highest speed for reasonably
safe driving. If there is an accident that causes you or someone else damage,
the court can use those signs as a way to say that you went against better
judgment and assign a greater punishment.

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.

~~~
asuffield
The punishment idea never really seems to deter drivers, and it has one
critical flaw: the punishment for driving like a maniac and causing a 10-car
pileup that killed a whole bunch of people is already that you didn't survive
it either.

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

------
gdne
All traffic laws do one thing: increase the likelihood that all drivers behave
predictably. Going a certain speed. Stopping at a stop light. Not changing
lanes erratically. It's all about being predictable to other drivers so they
have time to react to your presence. Being unpredictable is the quickest way
to get into a collision. Speeding but being predictable is a lot safer than
going the speed limit and swerving erratically.

------
rollthehard6
An interesting rhetoritcal question is what will be a suitable speed limit
when we have roads that are 100% autonomous vehicles?

------
mbleigh
I used to live in Atlanta where all of the major highways were capped at 55
around the city. The average highway speed was probably 75-80. If you drove
the speed limit, you would be the most dangerous car on the road by forcing
the flow of traffic to run around you.

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

------
tunesmith
Raising the speed limit to the 85%/15% ratio isn't necessarily the safest way
to handle the driving. If there's a road where more than 15% of drivers are
going faster than the speed limit, one option is to raise the speed limit, but
the other option is to change the road so people won't drive so fast on it.

~~~
colanderman
That would likely make the road more dangerous for the 85% who drive under the
limit. Like any engineering project, roads must be designed with headroom…

~~~
mikeash
That doesn't have to be the case. There are ways to make a road where people
_want_ to drive more slowly but that isn't any less safe.

------
Houshalter
Since this is HN, what about technological solutions? Better speeding cameras
could enforce speed limits universally. Self driving cars would obey speed
limits automatically, however they could safely drive at much faster speeds
than humans (albeit with significantly reduced fuel efficiency, which I think
will be an issue.)

------
satyrnein
The assumption is that there's no enforcement mechanism, so you might as well
give better guidance to the few people who comply voluntarily.

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

~~~
greggman
Well I don't want to die but I also don't want the ticket. In SF between
Candlestick Park and Oakland the speed limit is 50 but most traffic goes
65-70.

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.

------
zephjc
The trick to speed control is to set the speed limit 10-20 mph slower than you
expect traffic to actually go, and never or infrequently enforce it until it
exceeds +20mph. This is the M.O. for many places already.

------
vjvj
Speed does not cause accidents. Bad driving does.

The two are sometimes, but not always, linked.

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

------
bsimpson
Using the article's logic, why have speed limits on country roads at all?

