22 ms·

Is Every Speed Limit Too Low?

293 points by malchow 12y ago

chiph 12y ago
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 12y ago
  "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.
Symmetry 12y ago
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.
- warfangle 12y ago
  Or by designing roads around encouraging bicycling and pedestrian safety: - 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.
- robert_tweed 12y ago
  Part of the idea behind the 85th percentile speed idea talked about in the article is that drivers understand the dangers around them and slow down accordingly. If there are a lot of pedestrians around, most drivers will slow down a lot. Not all of them, but that's why you ignore that last 15%. 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.
- wahsd 12y ago
  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-related_death_rate http://en.wikipedia.org/wiki/List_of_countries_by_traffic-re...
  - nostromo 12y ago
    Per-capita is a bad way of measuring auto-fatalities. 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.)
    - aetherson 12y ago
      Per mile is much better, but also not that good. There are a lot of variables here. How much of driving is at freeway speeds versus how much at lower speeds (where even worse accidents are less likely to cause fatalities)? How good is trauma care in that country (which can turn what would be a fatality in country A into an injury in country B -- and note that part of how "good" trauma care is has to do with how remote from a hospital traffic accidents are)? How modern are vehicles in that country, and what percentage are what kinds of vehicles (air-bag equipped modern cars are much safer than older cars, which are in turn much safer than motorcycles)? What kind of intersection traffic control is there? How good are the roads?
tunesmith 12y ago
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 12y ago
  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 12y ago
    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.
- thaumasiotes 12y ago
  This only makes sense as a solution to the problem "some people are going faster than the little sign says they should". By design, it doesn't make anyone any safer; it makes them less safe. What problem are we trying to solve?
- peatmoss 12y ago
  Exactly. Ideally, speed limits are an expression of policy that reflect the normative values and desires of a jurisdiction. The best case would be for us to build roadways that reinforce those values. 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.
_archon_ 12y ago
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?
- mcdougle 12y ago
  You do raise a good point. I know that, when I started driving, my dad taught me a neat trick: drive 8.5 mph over the speed limit, and you'll never get pulled over. That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops. If you go any more than 8.5mph over, though, you might accidentally cross that 10mph mark, and if a cop's around he'll get you. And, sure enough, any ticket I've ever gotten is because I was going over 10mph faster than the speed limit.
  - incision 12y ago
    >'That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops.' 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.
peatmoss 12y ago
This article ignores a lot of peer-reviewed literature from planning, public health / injury prevention, and civil engineering in favor of some folksy wisdom of a lieutenant cop. A good starting mental model is that vehicle speeds increase both the frequency and severity of crashes. The article weakly, and quietly made an argument that I do agree with. Namely, roadway design needs to accompany speed limits to ensure people actually drive the desired speeds. Wide lanes, big setbacks, homogenous environments encourage speeding regardless of what is posted. But let's be clear, we should have our design follow our policy, not our policy follow bad designs that were put in place by roadway engineers of yesteryear. That message seemed to be lost in the race to tell us something tantalizingly counterintuitive. I love "everything we know is wrong" storytelling as much as the next guy, but only when that's actually backed up with solid evidence. Take for example this gem from the article: > “We all speed, yet months and months usually pass between us seeing a crash,” Lt. Megge tells us when we call to discuss speed limits. “That tells me that most of us are adequate, safe, reasonable drivers. Speeding and traffic safety have a small correlation.” That would seem to be at odds with this peer reviewed article (sorry, paywall, but you can read the abstract): > Respectively, they found evidence for an exponential function and a power function between speed and crash rate. Both types of studies found evidence that crash rate increases faster with an increase in speed on minor roads than on major roads. At a more detailed level, lane width, junction density, and traffic flow were found to interact with the speed–crash rate relation. Link to article: http://www.sciencedirect.com/science/article/pii/S0001457505001247 http://www.sciencedirect.com/science/article/pii/S0001457505... Priceonomics's banner ad tells me it is selling a new book titled "Everything is Bullshit." Quite right.
- tux1968 12y ago
  There is conflicting evidence on the matter. A local (Vancouver) video[1] circulating here had some strong arguments that our speed limits are kept needlessly low. If you're interested in such things, it's a well done video and worth the 15 minutes it takes to watch. [1] http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vancouver-roads/ http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vanco...
  - 12y ago
cheald 12y ago
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_report.pdf http://www.mdt.mt.gov/publications/docs/brochures/safety/hsp... [3] http://missoulian.com/news/local/report-montana-highway-death-rate-rd-highest-in-u-s/article_f0baa0c4-9998-11e3-8d21-001a4bcf887a.html http://missoulian.com/news/local/report-montana-highway-deat... [4] http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in_U.S._by_year http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in...
- peatmoss 12y ago
  I've always loved this example. I lived in MT pre, during, and after this experiment. We went from: - 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.
  - 12y ago
mwfunk 12y ago
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.
cfstras 12y ago
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.
- Cakez0r 12y ago
  I think it would work to just make the inside lane unrestricted and only have speed limits on the outer lanes. That way, slow and fast drivers aren't endangering each other because they're in completely separate streams of traffic.
  - cfstras 12y ago
    Except that could encourage people to stay out of the right lanes -- leading to confusion or wasted lanes when trying to pass people, which happens all the time. If you closely watch a german highway, there are 2 to 3 lanes (per direction) for the most part, and the speeds are quite consistent: The rightmost lane is full of trucks going 60 mph (90-100 km/h), while the middle lane is going around 80 mph (130 km/h), which is the advised speed, or Richtgeschwindigkeit. The leftmost lane is left exclusively for passing slower cars and those going 100+ mph (160+ km/h).
- chadgeidel 12y ago
  I'm sure you hear this all the time, but it's my understanding that US drivers are not nearly as well "trained" as German drivers. Anecdata, yes yes. It's trivially easy to acquire and maintain a driving permit here in the States, and it shows. (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.)
3pt14159 12y ago
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.
- chrishacken 12y ago
  Excellent example. I've noticed a few roads by me that are marked for 45mph that made me think, "woah, that speed limit is quite high for this road", but then I realized that it's actually on-par with the actual speed that people drive on that road (40-45). Then, there are other roads that are marked for 30mph that everyone drives 50mph on and you wonder wtf they were thinking when they set that limit. 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?
- pchristensen 12y ago
  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.
  - 12y ago
lutorm 12y ago
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.
zephjc 12y ago
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.
saticmotion 12y ago
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 12y ago
  In the US, automated cameras are generally limited to capturing people driving through red lights, if they are used at all.
  - apendleton 12y ago
    In many urban areas there are speed cameras as well. I live in Washington, DC, and there are lots.
- snowwrestler 12y ago
  There are automated speed cameras in the U.S. I know of several in the DC area. They seem to be calibrated a bit over the posted limit, probably to cover themselves for variance in the accuracy. Cars who know where the cameras are drive whatever speed they want until the immediate vicinity of the camera, where they slow down to just over the posted limit. Then they speed back up again. Drivers who don't know about them either follow the social cues ("hey, everybody else is slowing down"), or get flashed for a ticket.
- corin_ 12y ago
  In the UK we have (only a recent thing, so afaik it's not massively common yet) "average speed" cameras - they take a photo of you at two points along a road, and calculate your average speed by how long it took you to get from A to B, then ticket you for speeding if it was too quick. That prevents people from just slowing down when there's a camera coming up.
bryanlarsen 12y ago
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 12y ago
  Sweden actually has a goal of zero traffic deaths overall. http://www.economist.com/blogs/economist-explains/2014/02/economist-explains-16 http://www.economist.com/blogs/economist-explains/2014/02/ec...
yason 12y ago
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 12y ago
  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'.
evjim 12y ago
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?
akgerber 12y ago
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.
- eru 12y ago
  That's why we need laws to establish strict liability.
- gabriel34 12y ago
  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
ajmurmann 12y ago
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.
mbleigh 12y ago
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.
moneybags4 12y ago
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 12y ago
  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).
jchrisa 12y ago
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.
djloche 12y ago
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 12y ago
  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 12y ago
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.
satyrnein 12y ago
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 12y ago
  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.
Houshalter 12y ago
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.)
ackfoo 12y ago
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 12y ago
  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 12y ago
    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
  - mnw21cam 12y ago
    And in France, they are. The speed limit is automatically lowered in bad weather. Tourists have been fined for not realising. http://en.wikipedia.org/wiki/Speed_limits_in_France http://en.wikipedia.org/wiki/Speed_limits_in_France
deleted 12y ago
[deleted]
bsimpson 12y ago
Using the article's logic, why have speed limits on country roads at all?
rollthehard6 12y ago
An interesting rhetoritcal question is what will be a suitable speed limit when we have roads that are 100% autonomous vehicles?
vjvj 12y ago
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.
DatBear 12y ago
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 12y ago
  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.
- alexmayyasi 12y ago
  Please use ctrl-f to skip to this part of the article: "So if drivers disregard speed limits, why bother trying to set the “right” speed limit at all?" Then let us know what you think.

293 points by malchow 12y ago

chiph 12y ago

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 12y ago
"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.

Symmetry 12y ago

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.

warfangle 12y ago
Or by designing roads around encouraging bicycling and pedestrian safety: - 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.
robert_tweed 12y ago
Part of the idea behind the 85th percentile speed idea talked about in the article is that drivers understand the dangers around them and slow down accordingly. If there are a lot of pedestrians around, most drivers will slow down a lot. Not all of them, but that's why you ignore that last 15%. 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.
wahsd 12y ago
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-related_death_rate http://en.wikipedia.org/wiki/List_of_countries_by_traffic-re...
- nostromo 12y ago
  Per-capita is a bad way of measuring auto-fatalities. 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.)
  - aetherson 12y ago
    Per mile is much better, but also not that good. There are a lot of variables here. How much of driving is at freeway speeds versus how much at lower speeds (where even worse accidents are less likely to cause fatalities)? How good is trauma care in that country (which can turn what would be a fatality in country A into an injury in country B -- and note that part of how "good" trauma care is has to do with how remote from a hospital traffic accidents are)? How modern are vehicles in that country, and what percentage are what kinds of vehicles (air-bag equipped modern cars are much safer than older cars, which are in turn much safer than motorcycles)? What kind of intersection traffic control is there? How good are the roads?

tunesmith 12y ago

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 12y ago
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 12y ago
  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.
thaumasiotes 12y ago
This only makes sense as a solution to the problem "some people are going faster than the little sign says they should". By design, it doesn't make anyone any safer; it makes them less safe. What problem are we trying to solve?
peatmoss 12y ago
Exactly. Ideally, speed limits are an expression of policy that reflect the normative values and desires of a jurisdiction. The best case would be for us to build roadways that reinforce those values. 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.

_archon_ 12y ago

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?

mcdougle 12y ago
You do raise a good point. I know that, when I started driving, my dad taught me a neat trick: drive 8.5 mph over the speed limit, and you'll never get pulled over. That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops. If you go any more than 8.5mph over, though, you might accidentally cross that 10mph mark, and if a cop's around he'll get you. And, sure enough, any ticket I've ever gotten is because I was going over 10mph faster than the speed limit.
- incision 12y ago
  >'That's (supposedly) because a ticket for anything less than 10mph is simply not worth it for the cops.' 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.

peatmoss 12y ago

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

tux1968 12y ago
There is conflicting evidence on the matter. A local (Vancouver) video[1] circulating here had some strong arguments that our speed limits are kept needlessly low. If you're interested in such things, it's a well done video and worth the 15 minutes it takes to watch. [1] http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vancouver-roads/ http://www.vancitybuzz.com/2013/09/speed-does-not-kill-vanco...
- 12y ago

cheald 12y ago

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_report.pdf http://www.mdt.mt.gov/publications/docs/brochures/safety/hsp... [3] http://missoulian.com/news/local/report-montana-highway-death-rate-rd-highest-in-u-s/article_f0baa0c4-9998-11e3-8d21-001a4bcf887a.html http://missoulian.com/news/local/report-montana-highway-deat... [4] http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in_U.S._by_year http://en.wikipedia.org/wiki/List_of_motor_vehicle_deaths_in...

peatmoss 12y ago
I've always loved this example. I lived in MT pre, during, and after this experiment. We went from: - 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.
- 12y ago

mwfunk 12y ago

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.

cfstras 12y ago

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.

Cakez0r 12y ago
I think it would work to just make the inside lane unrestricted and only have speed limits on the outer lanes. That way, slow and fast drivers aren't endangering each other because they're in completely separate streams of traffic.
- cfstras 12y ago
  Except that could encourage people to stay out of the right lanes -- leading to confusion or wasted lanes when trying to pass people, which happens all the time. If you closely watch a german highway, there are 2 to 3 lanes (per direction) for the most part, and the speeds are quite consistent: The rightmost lane is full of trucks going 60 mph (90-100 km/h), while the middle lane is going around 80 mph (130 km/h), which is the advised speed, or Richtgeschwindigkeit. The leftmost lane is left exclusively for passing slower cars and those going 100+ mph (160+ km/h).
chadgeidel 12y ago
I'm sure you hear this all the time, but it's my understanding that US drivers are not nearly as well "trained" as German drivers. Anecdata, yes yes. It's trivially easy to acquire and maintain a driving permit here in the States, and it shows. (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.)

3pt14159 12y ago

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.

chrishacken 12y ago
Excellent example. I've noticed a few roads by me that are marked for 45mph that made me think, "woah, that speed limit is quite high for this road", but then I realized that it's actually on-par with the actual speed that people drive on that road (40-45). Then, there are other roads that are marked for 30mph that everyone drives 50mph on and you wonder wtf they were thinking when they set that limit. 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?
pchristensen 12y ago
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.
- 12y ago

lutorm 12y ago

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.

zephjc 12y ago

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.

saticmotion 12y ago

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 12y ago
In the US, automated cameras are generally limited to capturing people driving through red lights, if they are used at all.
- apendleton 12y ago
  In many urban areas there are speed cameras as well. I live in Washington, DC, and there are lots.
snowwrestler 12y ago
There are automated speed cameras in the U.S. I know of several in the DC area. They seem to be calibrated a bit over the posted limit, probably to cover themselves for variance in the accuracy. Cars who know where the cameras are drive whatever speed they want until the immediate vicinity of the camera, where they slow down to just over the posted limit. Then they speed back up again. Drivers who don't know about them either follow the social cues ("hey, everybody else is slowing down"), or get flashed for a ticket.
corin_ 12y ago
In the UK we have (only a recent thing, so afaik it's not massively common yet) "average speed" cameras - they take a photo of you at two points along a road, and calculate your average speed by how long it took you to get from A to B, then ticket you for speeding if it was too quick. That prevents people from just slowing down when there's a camera coming up.

bryanlarsen 12y ago

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 12y ago
Sweden actually has a goal of zero traffic deaths overall. http://www.economist.com/blogs/economist-explains/2014/02/economist-explains-16 http://www.economist.com/blogs/economist-explains/2014/02/ec...

yason 12y ago

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 12y ago
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'.

evjim 12y ago

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?

akgerber 12y ago

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.

eru 12y ago
That's why we need laws to establish strict liability.
gabriel34 12y ago
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

ajmurmann 12y ago

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.

mbleigh 12y ago

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.

moneybags4 12y ago

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 12y ago
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).

jchrisa 12y ago

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.

djloche 12y ago

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 12y ago
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 12y ago

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.

satyrnein 12y ago

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 12y ago
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.

Houshalter 12y ago

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.)

ackfoo 12y ago

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 12y ago
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 12y ago
  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
- mnw21cam 12y ago
  And in France, they are. The speed limit is automatically lowered in bad weather. Tourists have been fined for not realising. http://en.wikipedia.org/wiki/Speed_limits_in_France http://en.wikipedia.org/wiki/Speed_limits_in_France

deleted 12y ago

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bsimpson 12y ago

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

rollthehard6 12y ago

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

vjvj 12y ago

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.

DatBear 12y ago

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 12y ago
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.
alexmayyasi 12y ago
Please use ctrl-f to skip to this part of the article: "So if drivers disregard speed limits, why bother trying to set the “right” speed limit at all?" Then let us know what you think.