This is an archive of past discussions about Speed limit. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page.
I challenge Duke Ganote in particular to provide a citation to back the assertion that opposition to limits is significantly based on the OECD study. The majority of drivers have no idea this exists at all, and those who do probably only come across it as part of a post-hoc rationalisation. There is also other research which clearly demonstrates the link between speed and severity and frequency of collisions, so that sounds a lot like cherry-picking. The statistical is not "weak", though it is possibly fair to describe it as inconclusive. Just zis Guy you know?12:33, 1 March 2006 (UTC)
Guy, I don't think I stated "that opposition to limits is significantly based on the OECD study". I cited and directly quoted from the OECD study as perhaps the most international, reputable synthesis study that questions "conventional wisdom" on speed limits. In essence, the OECD study states that it is possible to conduct an rock-solid speed study, but that most studies are controvertible or, as you stated, inconclusive. That's exactly what the opposition says, but they will usually controvert studies done in their own country. The article needs to be more concise and international, hence the international citation. Duke Ganote02:11, 4 March 2006 (UTC)
mph and km/h equivalents rounded to nearest 5 units
Why are all the equivalent mph or km/h speeds in this article rounded to the nearest 5 units? For example, 110km/h is equivalent to 68mph, not 70mph. Likewise, 70mph is equivalent to 113km/h, not 110km/h. I see no good reason to round all the equivalents to the nearest 5 units. It is inaccurate, misleading and unnecessary. NFH21:29, 5 March 2006 (UTC)
I've found the answer. Anonymous user:24.146.12.62 inexplicably changed almost all the equivalent values on 2 January2005, rounding them to the nearest 5, thereby making them incorrect. See [5]. What's the easiest way to revert this very old edit (which could almost be called vandalism)? NFH22:26, 6 March 2006 (UTC)
Rounding to the nearest 5 makes the numbers more user friendly and better correlates to actual speeds that normal people would think about. I talk in terms of 55 or 75 mph, not 62 or 57 mph. If you see rounding errors, such as 70 mph being rounded incorrectly to 110 instead of 115, then please correct it. Otherwise, keep the 5 mph increments. Nova SS04:01, 7 March 2006 (UTC)
I don't see how rounding to the nearest 5 makes the numbers more user-friendly. Rounding to the nearest 5 km/h is ridiculous, given that km/h speed limits are in increments of 10. Why not therefore round to the nearest 10 km/h? Even mph speed limits in the UK are always in increments of 10. Apart from mph speed limits in the US, using increments of 5 is irrelevant to how most people think about speed limits. In any case, it makes absolutely no sense to round the equivalents in such a way that makes them inaccurate and misleading. Wikipedia should be accurate and not mislead. If I drive through a 30 mph speed warning device in the UK at 33 mph, it flashes up that I am doing 33 mph, and it does not round it to 35 mph. If I get stopped for speeding in France at 129 km/h, then the gendarme will tell me I was doing 129 km/h, and he does not round it up to 130 km/h. This rounding was introduced to the article by an anonymous user with no explanation of justification and should be reverted. NFH07:18, 7 March 2006 (UTC)
There have been other attempts at un-rounding numbers in the past few months, and they have been reverted. Please do not change rounding unless you have a consensus. By the way, I am fine with rounding km/h limits to 10 kmh increments. That being said, I am aware that some countries use kmh increments that end in 5 (35, 45, 55, etc) on advisory speeds, so that rule will need some flex. Nova SS16:19, 7 March 2006 (UTC)
By the way, you may need to check your glasses. This user's Jan. 2, 2005 edit has nothing to do with changing rounding practices on existing numbers. [6] All he did was correct one number that was rounded unlike every other number on the page. Here are all of this user's edits: [7]. Nova SS04:15, 8 March 2006 (UTC)
No, sorry you're wrong. See the link that I posted above, which I'll repeat again here for your benefit: [8] The anonymous user changed a large number of equivalents so they became incorrect. I'm not the one who needs glasses. NFH07:39, 8 March 2006 (UTC)
Ooops, you're correct. I neglected to remember that I was only looking at the first 50 of that user's changes. Sorry! Nova SS14:56, 8 March 2006 (UTC)
The only rouding that seems contentious to me on rounding is 100 km/h. In the article it's rounded to 65-mph consistently. However, it makes more sense to me to consistently round to the nearest 5-mph increment, which would be 60-mph. Conceptually, I remember the conversions using: 40 km/h = 25-mph; 80 km/h = 50-mph; 120 km/h = 75-mph. Duke Ganote15:57, 1 April 2006 (UTC)
Taiwanese maximum and minimum speed limits are to be posted in increments of 5 km/h, though most are posted in increments of 10 km/h. I have heard of a minumum speed limit of 25 km/h in a Hong Kong tunnel.--Jusjih14:12, 3 May 2006 (UTC)
Please vote below for the units to which you think equivalent speeds should be rounded. Please add Support votes above Oppose votes for ease of counting.
Round to the nearest 1 mph or 1 km/h
Support - this balances accuracy with ease of reading, i.e. no decimal places, and is the most natural. NFH21:18, 7 March 2006 (UTC)
There's a good reason why speed limit signs don't end in anything but 5 or 0. That reason also applies to this page.
Usability is more important than absolutle accuracy. Absolute accuracy in this case is a false benefit because nobody is going to print this out and use it to determine speeds.
People think in terms of what appears on the speed limit signs. This means 5 mph increments (10 kph increments), and using such increments makes the page more user friendly. Otherwise, users have to mentally pause and figure out which 5 or 10 increment we're talking about. I can tell you how 70 or 80 mph feels, but it's less intuitive for me to tell you how 73 mph feels.
If ending with 5 or 0 is not accurate enough, why not carry out to decimal places? Where does it end?
Oppose except for speeds slower than 20 km/h or 10 miles per hour. For faster speeds, the nearest 5 km/h or miles per hour are good enough, but for slower ones, the nearest 1 km/h or mile per hour is more accurate.--Jusjih14:17, 3 May 2006 (UTC)
Support. Limits are set in only one unit, not both. They are rounded in that unit for ease of both memorization and reading off the speedometer. The speedometer will usually be calibrated in the same units as the speed limit. Readers are not using this article in the same context as the posted speed limits, therefore they should be accurate. Rounding up or down to the nearest 1 or even 2 mph is sufficiently accurate. 5 mph is too far away in most cases.--Rfsmit19:25, 22 May 2007 (UTC)
Round to the nearest 5 mph or 5 km/h
Oppose - speed limits in multiples of 5 are unusual except in the United States and such rounding makes the data on this page inaccurate. NFH21:18, 7 March 2006 (UTC)
Support - this is typical practice in the US highway industry, including the MUTCD and AASHTO green book. It's known as a hard conversion. Rounding to the nearest 1 kph would be a soft conversion, which is deprecated unless accuracy is essential. Toiyabe22:35, 3 April 2006 (UTC)
Support for both km/h and miles per hour except for speeds slower than 20 km/h or 10 miles per hour.--Jusjih14:18, 3 May 2006 (UTC)
Oppose - This is inaccurate and dumbs down the article. I expect to see precise information in an encyclopedia. Please don't second guess what I might be using the information for. --Rfsmit19:47, 22 May 2007 (UTC)
Round to the nearest 10 mph or 10 km/h
Oppose - this introduces extreme inaccuracy. For example, 40 mph is equivalent to 64 km/h, but if rounded to 60 km/h, makes it 7% off from the true value. NFH21:18, 7 March 2006 (UTC)
Oppose. With conversions to 1 sig. fig., you might as well leave them out, because people will be reaching for their calculators anyway.--Rfsmit19:48, 22 May 2007 (UTC)
What the manual of style says
From the Wikipedia Manual of Style
Converted values should use a similar level of precision as the source value. For example, "the Moon is 380,000 kilometres (240,000 mi) from Earth", not "(236,121 mi)".[9]
Based on that, it does not make sense to be more precise than to the nearest 5 kph or mph since they are ultimately pretty similar units of measure (i.e., they are equally useful for measuring distances between locations that humans normally travel).
I think this shuts down the debate in favor of rounding everything to the nearest 5.
Disagree. It says is if n digits of precision used in one measurement, then use n in another. So for example a 50 km/h limit which is specified in legislation (not 51 or 49) then two digits are used so this should be translated to 2 significant figures in some other units hence, 50km/h becomes 31mph, 46fps and 550 inches per second. Softgrow07:56, 18 May 2006 (UTC)
Precision says that it is the units of the least significant digit of a measurement; for example, if a measurement is 17.130 meters then its precision is millimeters (one unit in the last place, or ulp, is 1 mm).
In that above example, the precision of 1 mm would not translate to a nice, round decimal value in the US measurement system. Therefore, the key concept is the smallest unit of measure used to determine a measurement.
In practice, the precision on posted speed limits is never more precise than every 5 or 10 units. Unless you want to revise the manual of style, it does not make sense to use a precision smaller than 5 whole units, whether it be kmh or mph. Nova SS13:59, 18 May 2006 (UTC)
Please read the section on history of Australian speed limits and comment on how rounding to the nearest 5 would work.
In the state of Victoria limits are enforced with a tolerance of 3km/h so a 100Km/h limit is 100+3/-0km/h (an effective limit of 103km/h). It is nonsensical to argue that the units digit has been rounded and the limit is 10 lots of 10km/h. The intent of the the legislation is quite clear as being to the nearest 1km/h so any translation should preserve that sense. The units of the limit should match the size of the practical tolerance. Softgrow01:16, 19 May 2006 (UTC)
You are missing the point of the conversions. This is not a driving manual. The purpose of the conversions is to provide an equivalent in terms that drivers using different systems can easily understand and relate. If I was going to Australia, then I would need to be sure I can read and understand kmh speed limits. But as I am sitting here in America, converting, say, 100 kmh to 60 mph makes more sense to me than 62 mph. I know what 60 mph is, but 62 is less intuitive.
Governments use no less than 5 unit increments on regulatory/advisory speed limits. When talking about speed limits in an article about speed limits, let's maintain this precision level in the conversions. When we are talking about other things, such as Australia's unreasonably small tolerance (about 1.86 mph), it may be fine to revert to 1 unit or even small precision.
Kilometers and miles are very similar types of measurement, so it makes sense to comply with the Manual of Style and maintain similar precision.
"Governments use no less than 5 unit increments on regulatory/advisory speed limits." Not true. In some parts of Chicago (for example) the posted speed limit is 12 MPH. I should get a pic of the sign sometime. --Kalmia04:25, 22 August 2006 (UTC)
Even if you find a picture, that would be a highly unusual exception and not relevant to the discussion. Nova SS13:42, 22 August 2006 (UTC)
(In response to Nova SS's previous comment) Actually, 62 mph is a better representation of 100 km/h than 60 mph, because it explains two things: 1. 100 km/h is equivalent but not equal to 60 mph, 2. 100 km/h is slightly faster than 60 mph. What valid reason is there for the article to remain dumbed down?--Rfsmit19:39, 22 May 2007 (UTC)
Minimum limits?
Across parts of Europe, a sign is defined for minimum speed limits - circular, white number on blue (UK). Are they any actual instances of these being used? 07:11, 14 March 2006 (UTC)
Last time I went through the Mersey Tunnel - a while ago now.
Essential Physics Section
The essential physics section is full of bad science. First of all, as stated in the referenced article, kinetic energy is proportional to velocity squared, not force. The relation between force (on the occupant, for example) and speed is less straight-forward but should be closer to directly proportional. The statement that the probability of a fatality is related to the fourth power of speed is actually taken from the reference, but that's still obviously bogus. The relationship in the reference shows a 100% probablity of fatality with a delta-V of 71 mph, which can be trivially proven to be false. The relationship may approximate x^4 for some portion of the curve, but certainly not for high speeds. Toiyabe23:26, 24 March 2006 (UTC)
The kinetic energy of a vehicle: E = 0.5 * m * v^2. Work done in a collision with an immovable object: W = F * d, where F is the average force exerted on the vehicle, and d is the distance over which that force is exerted. So, F = .5 * m * v^2 / d , neglecting other energy sinks (this is a conservative neglection - including other energy sinks would decrease the average force calculation). The problem is that d is also going to be dependant on v. If the object that is collided with does not deform, d will be how much the vehicle crumples. That is dependent on velocity. The relationship between d and v will vary from vehicle to vehicle, and probably can only be determined experimentally through crash tests. If d is directly proportional to v, then average force is also directly proportional to v. Most likely, average force is proportional to something between v and v^2.
Now average force is not peak force. Peak force will also be highly dependent on the design of the vehicle. Also, depending on how well the occupant is restrained, the peak acceleration of the vehicle may not be the peak acceleration on the occupant. Anyway, this all may be needlessly complex, and if it was covered in the article, it could really use some input from an expert to fill in the gaps. Why not just say that the kinetic energy involved in a collision is proportional to velocity squared?
If you say that the probability of anything is proportional to x^4, then it follows that there is some value of x where the probability is greater than 1 (in this case x > 71 mph), which is a bogus concept. The true curve for probability of fatality vs. speed is almost certainly an 's' type curve, with a low slope at low speeds and asymtopic to y = 1 at very high speeds. The initial portion of the curve may be approximated by x^4, but it won't be for high speeds. In this case, the article should say something like "The probability of a fatality is proportional to the fourth power of the speed change at impact for typical highway speeds". Toiyabe16:07, 27 March 2006 (UTC)
Original Research in 85th percentile rule
I have removed the following section that cites unpublished research (The section was previoulsy removed as POV when it lacked a source). Please refer to WP:NOR. To quote:
"Original research is a term used on Wikipedia to refer to material added to articles by Wikipedia editors that has not been published already by a reputable source. In this context it means unpublished theories, data, statements, concepts, arguments, and ideas; or any new interpretation, analysis, or synthesis of published data, statements, concepts, or arguments that, in the words of Wikipedia's co-founder Jimbo Wales, would amount to a "novel narrative or historical interpretation".
While at first glance this may appear to be a small adjustment, this effectively shifts speed limits from criminalizing only the fastest 15%--per the 85th percentile rule--to criminalizing the majority of drivers. A review of several Dallas-area speed limits shows that by setting speed limits on average 8 mph below the 85th percentile speed, 70% of drivers are criminalized. [10]
The following quote from a NHTSA publication may serve as a partial replacement:
"Despite the fact that speed directly relates to the severity of a crash, the motoring public generally does not view speeding as a safety problem. Further, speed limits are generally viewed as guides with few, if any, consequences for being ignored.
Unfortunately, the highway profession has done little to change this perception. In fact, many things are done to reinforce the perception by drivers that speed limits are only guides including: posting speed limits far below the design speed of the highway; posting speed limits far below the 85th percentile speed; inability or unwillingness of enforcement agencies to enforce speeding violations; and, unwillingness of courts to adequately penalize offenders." Toiyabe22:49, 3 April 2006 (UTC)
This whole 85th Percentile thing should be deleted from articles solely dealing with current speed limit. It's only realevent is it was one of the first methods used to initally set speed limits in the early 20th century. (This was prior to there being a large set of existing roads to compare to.) You certinatly can't beat a speeding ticket by claiming more than 15% of people go as fast as you do on that strength of road. Jon16:06, 25 May 2007 (UTC)
Totally untrue. In many instances, especially roads with no speed-related safety problem, the 85th percentile speed is still the only factor that goes into applying speed limit. In fact, in Texas, the 85th percentile speed is the only mandatory factor in determining a speed zone. Other factors may be considered but are optional. Nova SS01:17, 1 June 2007 (UTC)
Boy, now _this_ article is some ugly mess... time to be bold.
First off, I've shuffled the sections around a bit and sorted the countries by continent, thereby hopefully making it a bit easier to navigate around. The Europe table has been spiced up, and the readings in mph removed as they cluttered the table quite a bit (with the exception of the UK, which still uses miles, so naturally they stayed there).
I suppose we'd be best off if entries for countries that still use miles list mph, and if countries that use km/h list km/h. Of course, no rule without exception; as the UK is pretty close to mainland Europe it'd be wise to list both measurements there. Elsewhere, let the Americans get a calculator...
I've tried to smooth out stuff a bit, moved inline URL references to the References section, removed some fluff and unbacked statements from the various countries' entries. The lower part of the article needs some serious copyediting, as it dwindles down into a desert of text. Any physicists around here that can spice it up a little? --Doco12:19, 21 May 2006 (UTC)
Sometimes government gets carried away with making really slow speed limits in areas where there have been several accidents; sometimes to as low as 20 or 30 km/h. Can anyone provide any reference to the legality of this? Is there a certain speed limit which is unenforcable from a legal standpoint because it is set too low? I'm specifically interested in Ontario laws. Before you ask, no, I'm not trying to fight a ticket. Thanks. --RedACE19:56, 13 June 2006 (UTC)
Basically that was accurcute around the time automobiles came into common usage in the US on what to set speed limits initally to in the states, but it's since become totally obsolete. Instead when a new road is built, they sign it similarly to existing ones. Jon18:17, 5 July 2006 (UTC)
Please stop posting nonsense original research like this. Wikipedia is not a place to try out new theories. Nova SS20:16, 5 July 2006 (UTC)
Request for Explanation
Can someone please write an explanation of the significance of the various columns in the table, so that those of us unfamiliar with German roadsigns can understand it? LuNatic06:30, 14 August 2006 (UTC)
Well, the first column is for town & city speed limits, second column is for expressway (semi-motorway, dual-carriageway) and out of city speed limits and the third column for motorways (or highways). VI and V columns are for expressway/out of city and motorways, but for towing vehichles or HGVs (lorries).
However, I do believe these diagrams need replacing. They must be very hard to understand for users outside of Europe. Using text in lieu of the diagrams may be the best approach. I will do this soon as I can --Luke w22:29, 24 August 2006 (UTC)
Germany
I think it is the same in every country that there are low speed limits if there are roadworks - this is the same anywhere
and does not belong here.
"... the insurance company may refuse to settle part of the bill if the driver...."
This has nothing to do with the speed of driving - only unsafe driving. This is just an assumption without any evidence.
Insurance companies would have to prove that the speed of driving was unsafe, which could only happen if the police happened to do a speed control at the same time - and then the safety distance to the other cars is decisive, and not the speed of the car unless it was foggy or there was a speed limit.
"Porsche vehicles, for instance, are known for not having this restriction, and many aftermarket car tuners offer to remove the limiter. "
Every garage can do that and there are many other cars withouth an artificial speed limiter. This is unfair advertising for Porsche.
Germany is not like the USA. "Federal states" are not difference from each other and laws are national laws and always apply to specific parts of a motorway due to a particular reason.
"Although the concept of a nationwide law restricting Autobahn speeds to 120 or 130 km/h has been on the agenda of various political and environmentalist groups for decades, there are no definite plans for this at present."
In fact there are no plans...not even indefinite plans.
Actually, some of this is not quite correct. The Autobahn and the major Landstrassen are quite simply federal roads, so there's no reason to even expect states to introduce speed limits there, but this isn't really relevant since a law would only be relevant for a national speed limit, not for a local one which is simply an administrative act with laws merely covering what happens if you get caught breaking it. --OliverH08:58, 2 October 2006 (UTC)
"A statewide binding speed limit of 130 km/h, for example, was established in Rhineland-Palatinate over a decade ago,"
To my mind, this is not quite correct. Rhineland-Palatinate imposed a speed limit of 130 km/h on the whole Rhineland-Palatinate part of the A 61 motorway, but still there are stretches of other motorways (e. g. A 60, A 63) still whithout speed limits. Posting speed limits or other restricitions state and local authorities must obey the frame conditions given by the road law (Straßenverkehrs-Ordnung, StVO). —Preceding unsigned comment added by 84.176.199.29 (talk) 20:39, 20 September 2007 (UTC)
Roads without speed limits - qualification
Nepal has been recently added to the list in this section, which is technically correct but average speeds in Nepal are 40-50 Km/h [11]. Whilst there are no limits vehicles never approach Autobahn-like speeds which a reader would expect from a road wihtout a limit. I've had a couple of attempts to fix this up but all look clumsy:
Put some sort of qualification (say can actually exceed 100km/h)
Leave Nepal in but point out the speeds are quite low in practice
Delete the reference to Nepal (but it will probably come back)
Certainly don't delete the reference. It makes the valid point that traffic speeds are controlled by factors other than legal speed limits. The entry could say something like "Nepal has average traffic speeds of 40-50 km/h and has no statutory speed limits set on any of its roads". -- de Facto (talk). 10:26, 25 January 2007 (UTC)
I can't see the link between paved roads in far rural BC and Nepal. The situation is quite different. I'm sure that people already drive faster than 40-50 km/h in rural BC. Alex Sims03:11, 3 March 2007 (UTC)
In my opinion, far rural BC and Nepal are similar in that "posted speed limits have little impact because they do not provide useful information that the driver needs to negotiate the rural area, especially during night time and inclement weather conditions." Duke Ganote02:46, 13 March 2007 (UTC)
Justification of speed limits
I was hoping to add a section on the justification of speed limits. I have heard a saying, "The right to swing my arms ends where the other person's nose begins". So, the justification of speed limits is other drivers have a right to be on a safe road that overrides other peoples right to speed. What about at night when there are no other drivers? Why is there still a speed limit? People have a right to slowly kill themselves by smoking, why can't they be allowed to put themselves at risk by speeding when no one else is around? —The preceding unsigned comment was added by Dragonsshadows (talk • contribs) 23:31, 3 March 2007 (UTC).
Italy
Actually the 150 km/h limit on some section of Italian "Autostrade" was approved but was never officially introducted.
In fact, the limit is valid only where is indicated, but as there is no section that shows a limit of 150, the maximum speed allowed in Italy is 130.
Also, on expressway the limit is of 110 km/h for cars and motorbikes (no different speed limit), valid only where if indicated.
Enforcement and ANPR
I've noticed a fact tag there and am wondering if the original editor meant to write about ANPR used for enforcement of speed limits and driving hour limits on heavy long distance vehicles such as the [Safe-T-Cam] in Australia, where cameras are hundreds of kilometers apart. Should I change the passage to reflect that approach or is there really a one mile apart based system? Alex Sims06:42, 22 March 2007 (UTC)
Speed Limit in Austria
I removed the 160 km/h limit because this particular speed test was limited to May and June 2006 and thus does not exist anymore. I kept the footnote (and enhanced it a little) because I think the fact that there was such a speed limit should also be recorded somewhere. See e.g. DerStandard
20 mph near many schools, neighbourhoods with no through route; some industrial estates and business estates
30 mph as a default speed limit for areas with streetlamps
40 mph for major through routes (with smaller “repeater signs” posted periodically to prevent the lower default kicking in)
50 mph for some “Urban Clearways” and suburban through routes (again with repeaters)
So the Within Towns column should have “20-50 (32-80 km/h)” or “20-50 (30-80 km/h)” depending on your view on rounding. Also, what counts as a “Town”? If villages and hamlets do then the range goes up to 70 mph (which is 113, 110 or 100 km/h, to 3, 2 and 1 sig. fig.). --Rfsmit20:00, 22 May 2007 (UTC)
Non-mandatory or “suggested” speed limits
In addition to mandatory speed limits, the UK has non-enforceable “suggested speed limit” signs. They look somewhat like the US signs, only they are wider, with "MAX SPEED" to the left. There is no corresponding “end of suggestion” sign. Do other countries have a similar thing? (While they're unenforceable, they could probably be used to support a charge of “driving too fast for the conditions”.) It seems the US uses mandatory limits where in the UK a suggested limit would be posted.--Rfsmit20:17, 22 May 2007 (UTC)
You will find such signs in the USA for road directional changes. For example, if you are coming upon a curve, the speed limit might be 55 miles per hour (90 km/h) but a yellow sign (example given) will have an arrow indicating the curve and also a sign directly below saying 25 miles per hour (40 km/h). If you are able to travel the curve at 55, that is not illegal. However, if you cause an accident, you would almost certainly be held responsible under the "driving too fast for conditions provision" or perhaps "reckless operation of a motor vehicle".--Analogue Kid20:52, 22 May 2007 (UTC)
Evidence that raising speed limits doesn't increase accidents and can actually make the roads safer and that the UK used the 85th percentile speed
From a pre obsession with "Speed Kills!" policies UK government document on speed limit setting:
ANNEX E TO DEPARTMENT OF TRANSPORT CIRCULAR ROADS 1/80
THE EFFECT OF ALTERING LEVELS OF SPEED LIMITS: SUMMARY OF EXPERIENCE
1. It is a common but mistaken belief that drivers allow themselves a set margin over the prevailing speed limit, and that if a limit is raised by 10 mph, they will travel 10 mph faster. In fact, an increase in an unrealistic speed limit rarely brings an increase in traffic speeds. ("Unrealistic" is here used to mean "substantially below the 85 percentile speed"). It is much more likely that there will be no change, or even a fall. It seems that drivers relieved of the frustrations of too low a limit rarely abuse the higher one. Indeed it is not unusual for the accident rate to fall when a poorly-observed limit is raised. This may mean that reduced frustration leads to changes in driving behaviour conducive to accident reduction.
2. The evidence for asserting that speeds and accidents do not increase in proportion to an increase in speed limit comes from studies made before and after unrealistic local limits have been raised. Some of the main evidence is summarised in paragraphs 3-9 below.
3. In 1960, a Departmental Road Safety Committee reporting on the results of the experimental introduction of 40 mph speed limits in the London area concluded that the raising of the limit had resulted in no appreciable change in speeds, while the accident rate remained substantially the same. The committee considered that the higher limit had achieved its purpose of removing unjustifiably low speed limits, and encouraging a proper standard of enforcement.
4. A before and after study carried out at 20 locations through Kent, where the limit had been raised from 30 mph to 40 mph, showed a fall in speed, or no change, in 80% of the measurements taken, and a small increase in the others. The total number of accidents fell by almost 20%.
5. In 1973 the Metropolitan Police produced the results of a study on six sections of trunk road where — in accordance with the Department's criteria — speed limits had been raised from 40 to 50 mph, or from 30 mph to 40 mph. At four locations the 85 percentile went up by less than 2 mph and at two locations it went down. Allowing for a general decrease in accidents, the reduction in the number of accidents at these places was 15%.
6. When the speed limit in Park Lane, London W1, was increased from 30 mph to 40 mph in 1970, the 85 percentile speed fell from 43.6 mph (measured in 1970) to 39.2 mph (measured in 1974).
7. In 1974, the Midland Road Safety Unit reported the results of a study of a large number of speed limit changes from 30 mph to 40 mph. Their conclusion that there had been no significant increase in either speeds or accidents was in line with the conclusions from a similar exercise for cases in other parts of the country carried out within the Department.
8. The Department has recently conducted a survey of the effects of changing the levels of speed limits in various parts of the country. The results indicate that raising speed limits has little effect either on the speeds of vehicles or the rates of accidents.
9. The following examples of local speed limit changes from 30 mph to 40 mph illustrate this point.
85th Percentile Speed Accident Rate
County Road Before After Before After
Cheshire A41 44 43 1.06 0.6
Lancashire B5253 43 37 0.78 0.85
West Yorkshire A58 40/43 47/52 1.45 0.65
Warwickshire A34 42/42 43/43 0.5 0.65
Warwickshire B4453 42/44 43/43 3.2 1
Surrey 40/42 47/40 41/41 45/37
The table above shows that, in the one instance in which speeds rose, the accident rate went down.
10. With the removal of the energy conservation speed limits in June 1977, the national speed limit went up from 50 to 60 mph on single carriageway roads and from 60 to 70 mph on dual carriageway roads. This afforded an ideal opportunity to judge if traffic responds to national speed limit changes in the same way as it does to local changes. A survey of speeds at 49 points throughout the country made in July 1977, compared with a similar survey in July 1976, showed that for cars and motorcycles with a headway of at least 5 seconds there was no change in the mean speed on single carriageway roads and a 1 mph on single carriageway roads and 2 mph on dual carriageway roads (sic). An analysis of national accident rates in the months following the changes shows no evidence that raising the limits caused any increase in the number of accidents.
=========
Here's an another (21st century? I forget the year) government document (link now dead) which confirms how speed limits were supposed to be set and tries to get rid of the 85th percentile rule by, not to put too fine a point on it, lying about it's effects:
Update of Circular Roads 1/93, Setting Local Speed Limits
Section 3: The underlying principles of local speed limits
This section identifies who is responsible for determining local speed limits on which roads and the underlying principles behind determining appropriate speed limits.
Responsibility for local speed limits
22. The Highways Agency is responsible for determining local speed limits on the trunk road and motorway network, and Local Traffic Authorities for determining local speed limits on the local road network. In this Circular, the term Traffic Authority is used to denote both the Highways Agency and Local Traffic Authorities.
23. It is essential that Traffic Authorities collaborate with the police throughout when determining or considering any changes to speed limits. It is also important that neighbouring authorities work closely together, especially where roads cross boundaries, to ensure speed limits remain consistent.
24. All speed limits other than the default national limits are made by speed limit order. Further details are set out in Section 4, The Legislative Framework. Traffic Authorities must follow the full consultation procedure, details of which can be found in The Local Authorities' Traffic Orders (Procedure) (England and Wales) Regulations 1996, before any new speed limit is introduced.
Considerations in setting local speed limits
25. A study of types of accidents, their severity, causes and frequency together with a survey of traffic speeds should indicate whether an existing speed limit is appropriate for the type of road and mix of use by different groups of road users, or whether it needs to be changed. It may well be that a speed limit need not be changed if the accident rate can be improved by other speed management measures. These alternative options should always be considered before proceeding.
26. There will be roads or stretches of roads that suffer from poor compliance with the existing speed limit. Where this happens and the speed limit is considered to be appropriate for the road, there may be a mismatch between the appearance of the road and the driver or rider's perception of the risks of a collision or injury. If local engineering and/or education solutions have been tried and the road is either unsuitable or inappropriate for major engineering changes some form of enforcement may be necessary. However, it is again vital that Traffic Authorities discuss this with the police force responsible for enforcement before any remedial action is taken.
27. Before introducing or changing a local speed limit, Traffic Authorities will wish to satisfy themselves that the benefits exceed the disbenefits. Many of the costs and benefits do not have monetary values associated with them but Traffic Authorities should include an assessment of
Benefits:
Accident and casualty savings
Reduced emissions
Improvement to the environment
Reduction in public anxiety
Reduction in severance by fast moving traffic
Improved conditions and facilities for vulnerable road users.
Disbenefits:
Increased journey times for motorised traffic
Cost of associated engineering or other physical measures and their maintenance
Negative environmental impact of engineering or other physical measures
Cost and negative visual impact of signing
Cost of enforcement.
The underlying principles
28. The underlying aim of speed management policies should be to achieve a 'safe' distribution of speeds which reflects the function of the road. This should mean an average speed appropriate to the prevailing conditions, and all vehicles moving at speeds as close to this average as possible.
29. The main purpose of local speed limits is to provide for situations where it is considered appropriate for drivers to adopt a speed that is lower than the national speed limit. However, that limit does not imply that it is a safe speed under all conditions and drivers should be encouraged to adopt still lower speeds if conditions warrant.
30. Any decision to change a speed limit must be taken with the full support of the police as they will be responsible for enforcing the new limit. If the new limit is set in isolation or is unrealistic it is likely that the police will not be able to enforce and the overall effect will have little impact on safety. It is also likely to cause problems if there are raised expectations in the local community but these are not delivered.
31. An important factor when setting a speed limit is what the road looks like to the road users, such as its geometry and adjacent land use. Drivers are likely to expect and respect lower limits, and be influenced when deciding on what is an appropriate speed, where they can see there are potential hazards, for example outside schools, in residential areas, and in shopping streets. A principal aim in determining appropriate speed limits should therefore be to alert drivers to changes in road geometry or environment.
32. However, different road users perceive risks differently and drivers and riders of motor vehicles do not have the same perception of the hazards of speed as do pedestrians, cyclists and equestrians. Furthermore sometimes the "messages" given by the road environment and geometry can be contradictory. Introducing or changing a local speed limit indicated by signing alone without accompanying education and effective engineering changes to the road itself is unlikely to have sufficient influence on driver behaviour to change actual speeds to below the new limit.
33. Speed limits should not be used to attempt to solve the problem of isolated hazards, such as a single road junction or a bend, since speed limits are difficult to enforce over such a short length. Other measures such as warning signs, junction improvements, superelevation of bends and new or improved street lighting are likely to be more effective. Similarly, the provision of adequate footways can be an effective means of ensuring pedestrian safety as an alternative to lowering a speed limit over a short distance.
34. As well as being a key indicator of whether a local speed limit is appropriate, the estimated collision and injury savings should also be a key factor when considering changes to a local speed limit.
35. The needs of vulnerable road users must be taken into account. Setting appropriate speed limits is an important element in urban safety management, with particular benefits for pedestrians and cyclists. Similarly as vehicle speeds are generally higher on rural roads, accident severity and the risk to vulnerable road users are also greater. Alerting drivers to the presence and needs of vulnerable road users should therefore be another principal aim in determining appropriate speed limits.
36. Drivers and riders of motor vehicles, pedestrians, cyclists and equestrians will also have different views about what speed is appropriate on rural roads. There is also a difference of opinion as to what constitutes a reasonable balance between risk of an accident, travel efficiency and environmental impact. Speed brings benefits in terms of shorter travel times for people and goods but with inappropriate speed for the conditions come costs, the greatest of which is death and injury to people. Sometimes, but not always, the appropriate speed will be lower than the speed drivers are choosing at present. An acceptable balance between costs and benefits needs to be sought so that speed management policies take account of environmental, economic and social effects as well as the reduction in casualties they may achieve.
37. Circular 1/93 advised the use of 85th percentile speed to determine local speed limits. This refers to the speed at, or below, which 85 per cent of the traffic is travelling. Viewed another way it is the speed only 15 percent of drivers exceed. Practitioners' thinking has evolved since then and many have expressed concern that 85th percentile speed can be heavily influenced by excessive speeds travelled by a minority of drivers. Some Traffic Authorities have therefore adopted the use of Mean speeds in assessing what is an appropriate local speed limit, as they are felt to better reflect what the majority of drivers perceive as an appropriate speed for the road. The Department shares this view and therefore recommends that mean speeds be used in future assessments of appropriate speed limits.
38. For the majority of roads there is a consistent relationship between mean speed and 85th percentile speed. Where this is not the case, it will usually indicate that drivers have difficulty in deciding the appropriate speed for the road, suggesting that a better match between road design and speed limit is required. The aim should therefore be to align the local speed limit so that it is not substantially higher than the original mean speed driven on the road, and to achieve an outcome where the mean speed is at or below the posted speed limit for that road.
39. Within routes, separate assessments should be made for each length of road of 600 metres or more for which a different speed limit might be considered appropriate. When this is completed, the final choice of appropriate speed limit for individual sections might need to be adjusted to provide reasonable consistency over the route as a whole.
40. The minimum length of a speed limit should generally be not less than 600 metres to avoid too many changes of speed limit along the route. In exceptional circumstances this can be reduced to 400 metres. Anything shorter is not recommended. The length adopted for a limit will depend on the limit applied and also on the conditions at or beyond the end points. Where a limit would otherwise end on a steep gradient, a sharp bend, humpbacked bridge or other hazard, the restriction may need to be extended to clear the hazard. Similarly, an extension may be required to provide good visibility of the speed limit signs. A limit may also need to be extended to cover any new access to an industrial or residential estate.
41. Occasionally it may be appropriate to use a short length of 40mph or 50mph speed limit as a intermediate transition between a length of road subject to a national limit and another length on which a lower limit is in force, for example on the outskirts of villages or urban areas with adjoining intermittent development. However, the use of such transitional limits should be restricted to sections of road where immediate speed reduction causes real difficulty or is likely to be less effective. Research and experience has shown that a 'countdown' system of successive short lengths of road with mandatory limits at gradually decreasing speeds is not effective, and it should be avoided.
Note that in section 37 the 85th percentile speed can **NOT** "be heavily influenced by excessive speeds travelled by a minority of drivers"! If you start with twenty speeds spread evenly from 5mph to 100mph the 85th percentile speed is 85mph. It doesn't matter if the 100th percentile increases to a million mph, or even if the 90th, 95th and 100th do: THE 85TH percentile speed is ***still*** 85mph!!!! What they are proposing is to criminalise not just those driving way above the speed most people drive at, but HALF of the people who drive at typical speeds. And as people are forced to drive below this "average" speed the average will fall enabling another reduction in the limit which leads to........
I'll leave it to the experts to edit this into the article.
Lack of speed limits in Indian States of UP and Kerala
As a resident of the state of Kerala I have myself responded to speed limits on highways in Kerala. If the article wants to prove otherwise, citations are needed rams81 (talk) 04:24, 3 April 2008 (UTC)
So there are defined speed limits for vehicles in Kerala, though it is usually sarcastically stated Kerala does not have speed limits. I am taking off Kerala from the list of places without speed limits. rams81 (talk) 19:45, 29 April 2008 (UTC)
German Version about streets without a general speed limit
