When driving on a highway with speed limits (which is pretty much every road except for the Autobahn) one can notice that most drivers break the limit by at least 5-10 km/h. Where the speed limit is seen as unreasonable (e.g. 4 lane highway, middle of the night, 80 km/h limit), most people would go 15-20 over if they know radar detectors are unlikely to be present. To me this shows that most drivers (and therefore most voters) would welcome an increase in highway speed limits, to (say) 160 km/h which is the maximum speed most people drive on the Autobahn.

But for some reasons the speed limits stay the same, to the point where New York has a limit of merely 105 km/h. So why aren't New York voters electing people who promise to raise the limits to something reasonable?

P.S. I'm not asking why the public won't raise the 50 km/h limit in cities - this limit does save a lot of lives and most people won't speed when pedestrians are nearby. Highways are a whole different beast.

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    You seem to assume that voters actually have an effect on speed limits. I suggest that revenue collection from traffic tickets is a more important factor. Also, a lot of those speeding voters tend to be in favor of speed limits &c for other people.
    – jamesqf
    Jan 2, 2018 at 18:21
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    You assume that if speed limits were 5-10 kph higher, the people who breaks these speed limits right now would not do the same. From the people I know, I think it is not as much a "This is the right speed for this road" but "This is how much i think I can get away without fines while breaking the speed limit" or "I am trying to do it as stated but sometimes I left myself go". And of course, some hard data about actual speed limit compliance would be nice.
    – SJuan76
    Jan 2, 2018 at 18:27
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    @SJuan76 actually, if you drive on the Autobahn (where there's no limit on at least 50% of the highway sections), you'll see that 90% of the people drive below 160 km/h, even though most modern cars can handle 200 km/h. If the limit was 160 on American roads I'm sure 90% would drive at 160 there as well. See the 85th percentile principle for further research. Jan 2, 2018 at 18:32
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    most people would go 15-20 over: I doubt that. Most people seem to drive according to the speed limit.
    – user11249
    Jan 2, 2018 at 20:18
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    Most people would probably whinge about the inconvenience of not being able to drive whatever speed they want...... right up until some idiot driving faster than they can manage takes out someone they know, someone cute and very young, or an equally cute family pet. Then they'd be completely outraged about why our politicians are letting these menaces to public safety fly around endangering responsible citizens, completely unchecked. In the USA, we have a deep, abiding desire to be victims in the spotlight, and want assurances of complete safety from any form of death. Jan 2, 2018 at 22:54

5 Answers 5


Essentially you have conducted a rough poll of motorway drivers and concluded that many would like to see a rise in speed limits. This may be true among people who often use the motorway It is less clear that people who don't often use the motorway would be equally keen.

In 2015 there was some discusion in the UK about raising the motorway speed limit to 80mph (about 130 km/h). It was never enacted. There were various reasons for this: It was suggested that it would generally increase speeds by 10mph, with as many people speeding, only now at 90mph. It would increase petrol consumption (at a time when the government was keen to be seen to be reducing CO2 emissions) Either drivers would have to separate, lowering road capacity, or safety would be compromised. There would be an increase in accidents, or the seriousness of accidents. The relative speed between cars and HGVs (speed limited to 90km/h) would be greater, again a potential source of collisions. Noise from motorways would increase, and there was opposition from people living close to the road. At the end of the day it was not felt to be worth the parliamentary time to investigate these issues properly and produce the legistlation necessary. (Then the referendum for leaving the EU came along and there was no parliamentary time for anything)

These same considerations apply in other jurisdictions: For every person who uses the motorway and wants to travel at 160km/h there are others who object to it on environmental or safety grounds. Your observation of drivers is not a representative sample of voters.

  • Could you further explain or link "drivers would have to separate, lowering road capacity"? If cars move 10% faster with 10% more space between them (a 2 second rule) that seems like the same capacity.
    – user9389
    Jan 3, 2018 at 18:32
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    Because the "two second rule" is a rough rule of thumb. Actual braking distances are quadratic in speed, and so separation should also be quadratic. In fact drivers don't observe this, so greater speeds lead to greater risks.
    – James K
    Jan 3, 2018 at 18:36
  • Re "drivers would have to separate", as a matter of observation, they don't do so (at least on western US highways). If anything, vehicle separation has decreased.
    – jamesqf
    Jan 3, 2018 at 18:36
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    @JamesK Braking distance is quadratic, but that's the same for the car in front of you. Assuming both drive at the same speed and have the same brakes (you have to assume something), actual distance you need is "reaction time times speed when starting to brake" which is linear in speed, and even constant when measured in time. (Note that 2 seconds is much more than average reaction time, so that leaves a huge margin to cover difference in brakes and starting speed). Only when suddenly e.g. a non-moving brick wall appears in front of you on the high way, the "quadratic" comes into play.
    – Sjoerd
    Jan 4, 2018 at 22:30

I think the premise of your question is faulty, or at least unproven. Most people I know drive according to the speed limit, and some people who do drive above the limit will admit they "shouldn't do that".

Either way, increasing the speed limit has several effects, which could be used as arguments against it. In The Netherlands the speed limit was increased from 100km/h and 120km/h to 100km/h and 130km/h in 2012. I'll focus mainly on this, since it eliminates many other variables such as road quality, driver license system, car type/age/quality, driver culture, etc.

The results from this are:

  • The total number of casualties increased, and it's plausible this was caused by the increased speed limit. This article gives a reasonably good overview (translated from Dutch):

    Driving at 130 km/h is more dangerous for two reasons says van der Wee: the chance something goes wrong is greater, and if something goes wrong the impact is harder. "If everyone would drive at the same speed it would be okay, but on 130-roads there are still trucks that can drive only 80 km/h. The speed difference is too large, en the larger the difference, the more lethal the impact: 1 km speed increase gives 3 to 4 per cent more change of a lethal accident".

    According to Rugebregt there is not yet enough information about 130-roads for hard conclusions. "For example, we don't know which accidents happened during the day, on some of those roads you can drive only 100 km/h. Those are crucial details". The numbers about 2016 won't be announced until later this year.

    Two experts seem to disagree in this article, but it's at least very plausible that the number of (lethal) accidents increased. It's a risk not everyone is willing to take just to drive 10 km/h faster (which shaves only minutes off most journeys).

  • Air pollution and noise pollution is higher with increased speeds; this is not just CO2 and the like, but also particulates and other emission which are harmful for people's health. This is one reason not all motorways have a maximum speed of 130km/h, but 100 or 120 km/h. For example the air quality for some areas are now higher than EU norms and noise will be increased by about 20% by the 10 km/h increase, having an impact on people living in the area as well as the environment.

  • The national police has stated they are worried that many people will now drive a little bit above the new limit, instead of adhering to the previous limit.

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    Where do you live that most people you know don't go over the speed limit?
    – Christian
    Jan 3, 2018 at 14:14
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    I have a hunch 'honoring' the speed limit varies quite a bit culturally. Even in the US it varies by location. I've lived in areas where 10+ is the norm. And places where (frustratingly) -5 seems to be the norm.
    – user1530
    Jan 3, 2018 at 16:36
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    @Christian The Netherlands and the UK. Are there people who speed? Of course. Are those people common? Also yes. But are they "most people"? I don't think they are.
    – user11249
    Jan 3, 2018 at 17:01
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    The article cited is partisan. There is still fighting over the 130 km/h in the Netherlands, and those opposing it will cherry-pick any number they can. 130 km/h was introduced at the end of 2012, and traffic deaths dropped in 2013, stayed at that lower level in 2014, rose in 2015 to the level of 2012 again, and stayed at that level in 2016. The article cites only the last increase. See e.g. statline.cbs.nl/Statweb/publication/… (column "personenauto's" )
    – Sjoerd
    Jan 4, 2018 at 21:43
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    In conclusion: "The total number of casualties increased [in The Netherlands], and it's plausible this was caused by the increased speed limit." is not supported by the actual numbers, except when cherry-picking.
    – Sjoerd
    Jan 4, 2018 at 22:02

The speed limit in the United States used to be 55 mph (a little less than 90 km/h). 65 mph (105 km/h) is the increased limit in New York.

Western states often have higher limits, e.g. 70 mph (112 km/h) or 75 mph (120 km/h).

The 55 mph speed limit was originally designed to reduce fuel usage. Most cars run most efficiently in the 45-55 mph range, so any speed over 55 mph is increasing the amount of fuel for the trip. While the national limit has been eliminated, the states could still support the original goal with lower and potentially better enforced limits.

Note that even someone who agrees with this logic in general may still want to go faster individually. After all, the difference is minimal in any individual trip. It's only in the aggregate that this makes a big difference.

It's also worth noting that US highways are not designed for speeds of 100 mph (160 km/h). They were designed for speed limits from 50 mph to 80 mph. This contrasts with the German autobahn, where high speeds are part of the design. Those sections that do not fit that have speed limits lower than 160 km/h (100 mph).

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    In the US the decision to set the limit at 55 was done in the 70s, at which time fuel efficiency suggested even lower speeds, but 55 was chosen as the lowest politically possible speed. Additionally, engineers design highways for considerably faster speeds than 55mph - unfortunately those design specs for the roadway are not considered when setting the speed limit because it has little to do with road characteristics. Jan 4, 2018 at 15:59

Because people don't respond to the existence of a law; they respond to the enforcement of a law.

If police everywhere were uniformly citing drivers for exceeding the speed limit by a few mph or kph, then there would be public pressure to either a) raise the speed limit, b) reduce enforcement, or c) reduce the cost of the citations.

Consider the pushback in virtually any jurisdiction over the use of red light cameras, which are set up to automatically generate citations for drivers who fail to follow specified rules for stopping at intersections. The linked Wikipedia article notes a number of jurisdictions where public backlash has limited or eliminated the use of red light camera systems. (My own city, San Diego, removed its 21 red light cameras in 2013 at the direction of the mayor, who had campaigned against them.)

  • "Because people don't respond to the existence of a law; they respond to the enforcement of a law." This is provably incorrect. If memory serves, a few decades ago researchers dug into what people thought of a type of laundry powder that eventually got banned in Florida. When asked whether it was better, they wholeheartedly answered yes a lot more after it got banned - because they could no longer get it in the researchers' opinion. Another example might be alcohol consumption during the prohibition era. Point being, people love to live at the limit or try the forbidden - enforcement or not. Jan 5, 2018 at 19:57
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    @DenisdeBernardy Could be, but my point with the red light cameras is that the underlying law wasn't the target -- it's still a violation to run a red light or turn right on red -- but the way it was enforced generated the sort of public pressure the OP was pondering. Jan 5, 2018 at 20:02

Speed limits generally work the way you describe: Many people drive at or below the speed limit. A few drive a bit faster. Very few drive a lot faster. And everyone knows this. Including the people setting up the signs. If the want almost everyone to drive below X (you can never make everyone drive slowly), they set the speed limit to X-10, and almost everyone will drive below X.

Just because people exceed the X-10 speed limit, doesn't mean they want to go over X, especially if it's dangerous. And they don't want a higher speed limit, because it's Ok if people exceed a speed limit that is a bit too low, but not Ok if people exceed a correct speed limit.

  • Yeah, that's the logic of politicians. But shouldn't the voters be demanding higher speeds for themselves? Jan 2, 2018 at 19:20
  • @JonathanReez: Why? I don't particularly want to drive faster than I do, at least on 4-lane highways (twisty mountain roads are another matter :-)) I imagine most people feel the same way.
    – jamesqf
    Jan 2, 2018 at 19:42
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    @JonathanReez It's anecdotal, but as someone who habitually follows the "5 over" 'rule', I've never encountered a road with a particularly annoying speed limit for the type of road that it was. The only exception are the annoyingly ambiguous "it's now 10-15 under the speed limit if children are 'present'" whatever that means. It's equally worth pointing out that aside from a few speed trap towns that are milking tickets for revenue, I've found it exceptionally rare to see police pull people over if they're going with the flow of traffic and not driving aggressively. Jan 2, 2018 at 19:46
  • As a general rule with Speed cameras, they are set up to flash at X+12 MPH where X is the posted limit.
    – hszmv
    Jan 2, 2018 at 20:34
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    I don't think this really answers the question. You seem to make the argument that people self-regulate and generally won't want to travel faster than the speed limit + 10MPH. But then you suggest that people will do the speed limit + 10, whatever that limit is, so it's better to set the safe speed as the limit + 10 rather than just the limit. Those statements seem pretty speculative (and contradictory) and don't at all address the issue of public policy. Jan 2, 2018 at 21:02

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