Talk:Speed limit/Archive 2

Because of their length, the previous discussions on this page have been archived. If further archiving is needed, see Wikipedia:How to archive a talk page.

Previous discussions:

Archive 1 (through Sept. 31, 2005)

Same sign for kmh and mph

Amazing that the same sign is used for km/h and mph. - Patrick 10:38 18 Jun 2003 (UTC)

I always thought they use a round sign with a red border for km/h, and a rectangular white sign with a black border and black lettering for mph. 64.50.192.206 14:12, 31 July 2005 (UTC)

The white circle with red border and black text seems to be standard, for both miles/hour and km/hour. Rather confusing as you say, albeit slightly less so than having to drive on the wrong side of the road ;) Ojw 18:45, 16 October 2005 (UTC)

The double sign thing is remarkably dumb, I think it would be a good idea to change it. SimonP 01:28 5 Jul 2003 (UTC)

Fixed dml

Driving too slow

One time a police officer in our area said that he stopped an older man for going 28mph on the interstate when the limit at the time was 55mph. He said that was an accident waiting to happen, that someone going the limit would have come upon him and been unable to slow down or move aside in time.

JesseG 02:34, Nov 20, 2004 (UTC)

Apparently, driving slower than average traffic speed is just as dangerous as driving faster than the average traffic speed (relative speeds, etc.) and I wouldn't be surprised if it was common to pull over drivers who are at the posted limit.

It's certainly bloody scary to be driving at the 50mph speed limit (through some motorway roadworks) while everyone else is doing 75/80mph on both sides of you... Ojw 18:45, 16 October 2005 (UTC)

IIRC, it's forbidden to drive slower than 30 km/h on motorways in Sweden. Also, the wikipedia article on Hsuehshan Tunnel claims there's a formal lower speed limit of 50 km/h there. Perhaps the article should contain a separate section on lower speed limits? --213.50.52.226 17:23, 4 December 2006 (UTC)

Talking about POV

and about hasty generalizations, the photos and captions in the enviromental speed limits section are used in a very POV manner, and has no place in the encyclopedia. They seems to have been removed before [1] for this reason, but were added again under the claim Photographs are not POV. [2]. Duh!!! That entire section certainly seems to need substantial work toward NPOV. -- Egil 10:38, 26 September 2005 (UTC)

The photogrpahs were only intended to illustrate that the 55 MPH speed limit was later reverted to 65 MPH. The guy who originally claimed POV was mistakenly saying that something was trying to be said about the number of cars using the road. That is totally false. The difference in cars just happens to be because of the times and angles at which I took both pictures.

I understand your point about POV, and I see how it can be taken that way. I will try to document stuff better that could appear to be POV.

Novasource 13:35, 26 September 2005 (UTC)

I've added more documentation. Let me know what else can be done to ensure it's truly NPOV. Novasource 18:15, 26 September 2005 (UTC)

Moving Interstate Highways Speed Limit content to here

I think we should move the speed limit stuff off of Interstate Highways and to speed limit. If you compare the two, you'll see that speed limit is far more thorough, covers more road types, and is more accurate. Given that speed limits are by far the most pervasive and probably the most contraversial road regulation, I think we are best served by keeping the speed limit info on its own page.

I suggest linking to the United States anchor on speed limit.

Novasource 16:29, 6 October 2005 (UTC)

This article is already big and excessively focused on US issues. I believe that a separate article discussing speed limits in the USA is justified. This could be wider than the current interstate-only article. - Just zis Guy, you know? ^[T]/_[C] AfD? 14:23, 24 December 2005 (UTC)

Variable speed limits

Is there an article for variable speed limit that we should link to? If not, it's worth noting that the UK has them (first one was M25 I think, which lowers its speed limit to keep the traffic moving rather than start-stop). Ojw 18:45, 16 October 2005 (UTC)

Statements that need references

I have moved several statements that need more references to this page. I could not find documentation backing them up.

Opposition

However, it is noted that the Autobahns have twice the fatality
rate of Britain's (speed limited) motorways, and that increasingly
Autobahn speeds are being limited.

I cannot find any clear documentation of this statement.

It's in IRTAD. - Just zis Guy, you know? ^[T]/_[C] :: AfD? 19:06, 5 November 2005 (UTC)

It may be significant that drivers have been found
to drive slower within 1km of home than on equivalent roads
further away.

Needs documentation.

A TRL report, I'll get the number. - Just zis Guy, you know? ^[T]/_[C] :: AfD? 19:06, 5 November 2005 (UTC)

Safety

(text about increasing or lowering speed limits)...sometimes by
(perversely) ''reducing'' average speeds: drivers are more willing
to obey a limit they see as "reasonable" (although it should be
noted that there is solid evidence that most drivers overestimate
their own skill).

Needs documentation.

Novasource 18:22, 5 November 2005 (UTC)

It's in death on the streets, several primary sources are cited. I'll find my copy and list them. - Just zis Guy, you know? ^[T]/_[C] :: AfD? 19:12, 5 November 2005 (UTC)

Thanks for the updates. I look forward to these statements being re-introduced to the main text once they are referenced. Novasource 03:04, 7 November 2005 (UTC)

Examples: a survey of British drivers found that 40% rated the overall standard of driving as bad, but only 2% rated their own driving as bad; 24% rated the overall standard as goo, 75% rated themselves good (Lex Motoring Plc, 1989); A survey of motorway drivers found that, on a scale of 1 (poor) to 5 (good) drivers rated themselves at an average 3.9, and rated other drivers at a mean 2.7 (Gallup for General Accident Insurance, 1989); see also McCormick I, et. al., "Comparitive perceptions of driver ability - a confirmaiton and expansion" Accident Analysis and Prevention, Vol. 18 no. 6, 1986 (these are from the refs in a 1989 book). According to Davis, the tendency of drivers to see themselves as better than other drivers is one of the most stable features of informed debate on road safety. - Just zis Guy, you know? ^[T]/_[C] (W) AfD? 22:18, 8 December 2005 (UTC)

Now here's a questionable comment:

According to the study the risk of death is twenty percent. 
Specifically, in a crash with a change in speed from 180 km/h to 100 km/h, 
the driver is exposed to a risk of death of twenty percent. If such a crash 
were immediately followed by a second significant decrease in speed, from 
100 km/h to 20 km /h the driver would be exposed to a second independent 
risk of death (ie assuming the driver and the vehicle emerged unscathed from 
the first crash) of twenty percent. The combined probability of death is 
approximately one in three. The risk is likely greater since the study 
implicitly assumes that the driver is healthy and the vehicle and safety 
devices are intact prior to each impact; an unlikely scenario prior to a 
second impact.

I would be amazed if you could come up with a collision which dumped 80 km/h and left the vehicles travelling at 100km/h in the way described; a crash of that magnitude is not guaranteed to leave both vehicles drivable at all, let alone capable of being controlled to a stop at 100 km/h - it would have to be a straight rear-end shunt wioth no oblique component. I think this is highly speculative. - Just zis Guy, you know? ^[T]/_[C] (W) AfD? 22:27, 8 December 2005 (UTC)

History?

This article (like so many in Wikipedia), while interesting, omits any context of why & how speed limits developed... For instance, Br's Ref Flag Law, or New York's first limit, 1904...? Trekphiler 10:42, 16 December 2005 (UTC)

Hey, thanks for volunteering to create a history section! :-) Novasource 03:58, 17 December 2005 (UTC)

notes

According to the Shell Book of Firsts. The first speed limit in the UK and was 2 mph in the country or towns under the Locomotives and Highways Act on th 5th July 1865

I concur with Senior Moments. In Britain The Locomotives on the Highways Act 1865 imposed a limit of 2 m.p.h. in towns and 4 m.ph. in the country. It also required motor vehicles to be preceded by a runner carrying a red flag which is why it was known as 'The Red Flag Act'. The law was repealed in 1896 when a new urban speed limit of 12 m.p.h was introduced with 14 m.p.h for the country. This was further revised in 1903 when the limit became 20 m.p.h.

1904 -- The maximum speed limit in most cities was 10 mph.

http://www.ci.nyc.ny.us/html/nypd/html/transportation/newpage5.html

http://www.iihs.org/research/qanda/speed_limits.html#12

14th November, 1896, Motorcar speed limit raised from 4mph to 14mph

The Locomotive and Highways Act 1896 was the first improvement in motoring laws to encourage motor vehicles. It lifted the retrictions set by the 1865 act and the then famous 'man with a red flag' who would walk 60 yards ahead of each vehicle, enforcing a walking pace of between 2 and 4mph.

Ohio

1908 -- The first speed limit was 20 mph outside municipalities, 8 mph inside municipalities
1926 -- 35 mph
1940 -- 45 mph
1941 -- 50 mph
12/1/42 -- Gas rationing and a 35 mph speed limit on all roads that had been in effect along the 
 East Coast for 7 months was extended nationally to conserve gasoline and rubber during
 World War II
8/15/45 -- 50 mph speed limit reinstated
1958 -- 60 mph daytime, 50 mph speed limit at night
1963 -- 70 mph for cars and 55 mph for trucks and commercial tractors on interstates;
 60 mph daytime and 50 nighttime on noninterstates
1974 -- 55 mph for all vehicles on interstates and most other highways
1987 -- 65 mph for cars on 900 miles of rural interstates, 55 mph for commercial vehicles weighing
 more than 8,000 lbs.
1991 -- 65 mph for cars on another 246 miles of interstates
1992 -- 65 mph on 209 miles of rural noninterstates
1996 -- Speed limits raised to 65 mph on designated urban interstates and rural highways for
 passenger vehicles and commercial buses

Source: Ohio Historical Society

Gam3 17:44, 26 February 2006 (UTC)

That's pretty accurate... my own website, which I'd wager pre-dates the OHS site, actually quotes from the Ohio Code. I spent way too long (back in the 1980s) in the dusty basement archives of the University of Dayton finding and photocopying that information that I posted starting here http://www.dma.org/~ganotedp/ogc_1912.htm

Duke Ganote 02:22, 4 March 2006 (UTC)

Truck limits

This section looks a lot like someone with an agenda. The obvious solution to passenger cars running into the back of trucks is to reduce the speed of the passenger cars, especially since many trucks are either governed mechanically or unable to reach greater speeds due to weight. The fact that passenger cars are badly driven is hardly a good argument for increasing the risk and severity of truck impacts! - Just zis Guy, you know? ^[T]/_[C] AfD? 16:28, 23 December 2005 (UTC)

But if you do that, then you get back to uniform speeds between trucks and cars, which eliminates the need for differential speed limits. The section is about differential speed limits.

By the way, can you cite any evidence of truck/car collisions in light of US speed limit increases in the past 10 years?

Novasource 18:10, 23 December 2005 (UTC)

You are, I think, missing the point. The limits for trucks are not set to be different, they are set because these lower limits are more appropriate for goods vehicles. There is a surprising degree of unanimity on this between jurisdictions (and incidentally lower limits have existed for a very long time int eh UK). If the fact that goods vehicles need to drive at moderate speed means that careless drivers drive into them, the solution is for the careless drivers to go slower as well! - Just zis Guy, you know? ^[T]/_[C] AfD? 22:10, 23 December 2005 (UTC)

Truck limits are set using the same rationale as limits around schools. Heavy vehicles have more mass. If they collide with a passenger car the force applied to the passenger car is much more than the passenger vehicle can cope with. E=1/2mv2. The fact that the truck driver is less at fault is not the issue. To quote from page 3 of the excellent reference provided by Novasource, "The primary reason for regulating individual choices is the significant risks drivers can impose on others. For example, a driver with a higher tolerance for risk may decide to drive faster, accepting a higher probability of a crash, injury, or even death in exchange for a shorter trip time. This driver’s decision may not adequately take into consideration the risk his choices impose on the other road users. Even a driver traveling alone who is involved in a single-vehicle crash may impose medical and property damage costs on society that are not fully reimbursed by the driver. The imposition of risks on others that are not adequately considered when the activity of a person or a firm affects their welfare is a primary reason for government intervention in many areas besides traffic safety, such as environmental protection and product safety." A lot of the content in the speed limit article is POV but it will continue to exist (and reappear) until the fundamental reasons (which exist in textbooks on the subject) are expounded. An article on crash mechanics if it doesn't exist would be a good start. Softgrow 00:32, 24 December 2005 (UTC) (feel free to fix the markup)

I still think this discussion misses the point. The truck speed limits section is simply about different speed limits for cars and heavy trucks. It is not a discussion about blanket speed limit reductions, nor is it a discussion of vehicular physics. Those are entirely different issues and deserve their own sections or articles.

The record seems clear that it is difficult to make a case for or against differential speed limits. Just because something is appealing on a 5th grade physics level does not automatically mean it is an effective regulatory tool to manage human behaviors. Humans tend to complicate things...

A check for POV in the whole article would be appreciated. I am interested to hear your perspective. Maybe start a new discussion topic?

Novasource 04:17, 24 December 2005 (UTC)

I've had a quick look for POV (it is Christmas Eve in my timezone) and there is a fair bit of it except for the sections that list of the actual speed limits (that should probably be hived off to separate articles such as Speed limits in Australia, USA speed limits to remove the USA centric nature of the article (particularly given the large number of states with differing legislation). As a rule the last paragraph in each section is worst.

Taking a book off my bookshelf, and turning to the speed limit chapter, what is missing is probably more important, namely

Discussion of risk taking behaviour
System limits (driver, curves, other road users etc)
Enforcement issues in rural areas
Advisory speeds are a bit thin in the article
Linking to other measures that lower speed (altering network connectivity, speed humps, rumble strips etc)
Interrelationship with overtaking
The list goes on .... Softgrow 07:35, 24 December 2005 (UTC)

By the way, crash causation is a very valid question with regards to truck speed limits. There is only "so much" regulation that a populace can bear. Do you use your regulation and enforcement resources to hassle the usually innocent party, or do you concentrate on the guilty ones?

Novasource 04:25, 24 December 2005 (UTC)

In this case the innocent party (trucks) is making an economic gain. If they put all the goods in smaller vehicles they can driver faster, but they don't.Softgrow 07:35, 24 December 2005 (UTC)

Your points echo my concerns. The reason trucks have lower limits is precisely as stated: the potential to do harm. These limits are entirely defensible and apply to many jurisdictions around the world. The fact that negligent car drivers crash into slower-moving vehicles is no kind of reason to let trucks pose more dager, if anything it's a reason to slow the cars down to the same speed! - Just zis Guy, you know? ^[T]/_[C] AfD? 09:55, 24 December 2005 (UTC)

How do you justify a regulation when there is nothing to support that it actualy accomplishes its intended purpose? Novasource 16:01, 24 December 2005 (UTC)

I added some UK ocntext (where we have a higher differential in limits than the "highest" in the original text. I also removed the long section on Texas as being far too parochial for what is supposed to be an article on speed limits, the concept, in a worldwide context. - Just zis Guy, you know? ^[T]/_[C] AfD? 10:21, 24 December 2005 (UTC)

In the future, please move these sections to the Talk page. I think that is how Wikipedia recommends handling stuff like that (after 10 minutes of wading through the obtuse Wikipeda help pages, I couldn't find the proper reference). Novasource 16:01, 24 December 2005 (UTC)

Pictures removed

I removed the two pictures of a road in Texas. We have far too much about Texas in this article (Texas is not the world!) and the captions were POV and they could as OR since no verifiable evidence is presented that either picture was representative of the general conditions at either time. On the M25 in the UK use of variable speed limits has substantially improved traffic flow by slowing traffic at times of high volume.

I am moving United States content to a different article. Novasource 16:01, 24 December 2005 (UTC)

Separate article for US speed limits

I have moved the US Speed Limit information to Speed limits in United States. It is clear that US speed considerations were dominating the article, and it is also clear that US practices are much different than in other countries, causing unnecessary contentious disucssions.

In the move, I removed the following statement due to the fact that it are no longer relevant in a US-only article:

In the UK, on non-motorway dual carriageways trucks are limited to 50mph and cars to 70mph. On motorways cars are subject to 70mph limits on and trucks are limited to 60mph by law (and often 56mph by mechanical governor).

Novasource 16:19, 24 December 2005 (UTC)

This is probably reasonable. What is important is that the discussion of libertarian opposition to speed limits does not overwhelm the balance of the article. Per policy, Wikipedia documents the balance of informed opinon. The balance of informed opinion on speed limits is that they are necessary. - Just zis Guy, you know? ^[T]/_[C] AfD? 16:48, 24 December 2005 (UTC)

Requesting cleanup of Safety section

I am requesting a cleanup of the safety section. It has statements that are contradictory, unnecessary verbiage (usually using too many words to describe simple concepts), it contains some uncited original research, and since there are differing views presented, it needs better citation.

I will try to work on it as I have time.

Novasource 20:40, 28 December 2005 (UTC)

I have cleaned up this section.

Novasource 03:14, 16 January 2006 (UTC)

85th percentile speed

I feel the following additions to the 85th percentile speed is original research and POV:

There are several reasons for this. Predominant among them is that it is standard, in the United States, for drivers to assume an implicit 5 - 10 mph "pass" on speeding — it is rare, for example, for someone to be given a speeding ticket for driving 70 mph on a road posted at 65 — therefore, speed limits are underposted for safety's sake. (Some, however, have argued that increasing speed limits would make roads safer by reducing speed variance.) Moreover, many roads that could be traveled safely (for the driver) at higher speeds are posted at 20 - 35 mph because they are residential, as fatality rates in pedestrian accidents increase dramatically from 20 to 40 mph.

Drivers in the United States should also know that underposted speed limits are less common in rural areas, and that on many rural roads the posted speed limit is the maximum safe speed at which the road may be driven; moreover, difficult conditions on such roads often call for speeds lower than the speed limit.

I am not aware of a perceived enforcement cushion being one of the reasons why speed limits are marked below the 85th percentile speed. It's definitely not the case in Texas; in fact, such a rationale for pushing speed limits lower probably wouldn't muster under the statute regulating reasons why speed limits can be lowered.

Also, I feel it is POV to say that "many rural roads the posted speed limit is the maximum safe speed at which the road may be driven". This is quite POV without citations.

Finally, my own research leads me to believe that underposting is consistently 5-15 MPH in rural and urban areas. As one example, the speed limits on virtually every highway outside the Dallas, TX area are posted 5-10 MPH below the 85th percentile speed (rounded to the nearest 5 MPH)[3]. States with 65 MPH maximum speed limits are likely even further below the 85th percentile speed.

Novasource 18:51, 9 January 2006 (UTC)

I think what needs to be added to this discussion is that setting a speed limit at the 85th percentile speed effectively means 1 in 7 drivers are imediately driving over the speed limit. I am sure that most people would not say every seveth driver on a road is driving too fast - but that is what the 85th percentile speed policy does.

AWE, 31 August 2006

Original Research in Speed limits, actual speeds, and aggregate safety

This section and others relies heavily on original research by Aren Cambre. This is unpublished research and is excluded from Wikipedia by policy. Additionally the paper from the TFHRC has been misquoted. Most not some, studies found a reduction/increase in speed limits gave a correlated reduction/increase in fatalaties/injuries. This section needs to be cleaned up to remove it's bias and to reflect the cited material correctly. (I'm not volunteering to do the edit right now, just flagging the issue for other editors). Softgrow 05:47, 16 January 2006 (UTC)

I see what you mean. I didn't intend to change the emphasis much; I just moved stuff around and eliminated redundancies. I was also making assumptions about what was in the content of both sites (TFHRC and Aren Cambre's site), and I didn't validate them well enough. Give me a chance to work on those issues. Also, I do not believe that Aren Cambre's site constitutes original research. It appears to just be a listing of research he found with certain quotations highlighted. If necessary, I could bypass his site and reference the research directly?

Novasource 15:59, 16 January 2006 (UTC)

Check it out now.

Novasource 16:24, 16 January 2006 (UTC)

Aren Cambre's site is original research. Have you read it? It is a collection of articles to support an argument and organised by topic. Have you noted that significant research that does not support his point of view is omitted? Wikipedia policy is to use the primary sources. These are articles that have been subject to peer review and are generally accepted.

You are still misquoting the article and presenting a particular POV and not allowing the sources to speak for themselves. Nine out of nine non US studies found a positive correlation between higher speed limits and overall crash risk. Of the ten US studies, five had a positive correlation, three found no significant change, one was mixed, and one (Lave and Elias (1994)) found a negative correlation. As a quick test for POV in an article this section fails. There are 12 lines. 9 of these should support the view that lower speed limits are safer, two should be for no correlation and one against. Its currently 2 support and ten against. Softgrow 22:56, 16 January 2006 (UTC)

I don't entirely agree with your interpretation of the studies (e.g., Parker (1997) also found a negative correlation, and it may be far more comprehensive than all the other studies), but I see your point about POV and original research. Could you clean it up in a way that is fair to both sides of the issue?

Novasource 04:10, 17 January 2006 (UTC)

I was hoping that you might :-) - I will do it though, just not straight away. Softgrow 05:02, 17 January 2006 (UTC)

OK. Be gentle to us "speed freaks." :-)

Novasource 15:52, 17 January 2006 (UTC)

Done, finally. 13 lines of what the study found. I was gentle to the "speed freaks". Softgrow 11:02, 1 February 2006 (UTC)

The article now purports "straightforward, positive correlations between speed limits, speed, and safety on freeways and other high speed roads". However, the FHWA Synthesis carefully delineates (a) the clearer correlation of speeds with crash physics and (b) the murkier correlation between speed and crash incidence. Most of the speed to crash correlation was studied on the basis of speed variance rather than absolute speed. While Fildes et al show a straight-forward, positive correlation in their graph, this is based on "self-reported crash data collected at roadside from motorists" according to the Synthesis. Can you show me where you found the straightforward, positive correlations? Duke Ganote 18:43, 3 February 2006 (UTC)

The summary paragraph 4 and the section "SPEED LIMITS AND SAFETY". The paragaph I have written should reflect what that article found. To go beyound that is original research. Softgrow 20:58, 3 February 2006 (UTC)

I see where you're looking now. Among other things, I'm concerned that while presenting the Synthesis summary the article (1) neglects to mention the "limited evidence that suggests the net effect of [motorway] speed limit [increases] may be positive on a system wide basis", an reference to Lave's work. (2) is a bit over- and mis-stated. The actual Synthesis statement is "on freeways and other high-speed roads, speed limit increases generally lead to higher speeds and crashes". Note that (a) it's a general not straightforward correlation; the Synthesis does cite Pant's research in Ohio and (b) a "positive correlation between speed... and safety" would imply that safety increases with the speed -- the opposite of the next sentence in the article.Duke Ganote 09:25, 6 February 2006 (UTC)

I've altered the text to clear up point (2) by quoting directly from the report rather than a sentence that was a modification of something that was there before. I didn't put (1) in as it was limited evidence suggesting something. The next synthesis article should be more definite one way or the other. Softgrow 10:57, 6 February 2006 (UTC)

Have you considered bulletizing the points? The frequent use of italics is, to my eye, rather distracting. Duke Ganote 12:08, 7 February 2006 (UTC)

I wanted to keep it compact (given the length of the article already). I have however changed the italics to quoted text that should look better. Softgrow 22:54, 7 February 2006 (UTC)

Yes, removing the italics is much more in keeping with the look of an encyclopedia article. Thank you. Note also that (1) is not a gratuitous summary aside by FHWA; it's subdued acknowledgement that a low motorway limit may suboptmize overall road safety by (a) shifting law enforcement away from high-accident roadways onto motorways and (b) shifting traffic away from safer motorways onto less-patrolled but more dangerous roads. Duke Ganote 03:58, 9 February 2006 (UTC)

Motorways section of Essential Physics

I appreciate the information added to Essential Physics about motorways, but I am concerned about it for a few reasons:

It duplicates content already on road safety. This setup can cause concurrency problems: if the motorways information on road safety is edited, then who guarantees that the same content on speed limit is edited, and vice versa?
It is not 100% related to speed limits. The study of motorways is one that involves many disciplines, and vehicle speed regulations are just one of these disciplines.

I think it may be better to have a quick summary that wiki-links over to the Road Design section of Road Safety rather than to copy everything.

Novasource 19:38, 24 January 2006 (UTC)

I'm inclined to agree. However, speed, speed limits, safety and roadway design are intertwined topics. I've updated the road safety section, and am looking at how to set up appropriate links. Duke Ganote 18:45, 3 February 2006 (UTC)

The speed limit article is getting a bit long. Something needs to go! (to another article). The interelationship between speed limits and safety would be an ideal candidate. A restructuring of the article could have

Why - rationale for speed limits (link to safety article)
How speed limits are set (85th, design, variable, blanket etc, discuss techniques used over time including current practice)
What speed limits are set where (table format, including urban limits, the article is very weak on urban) Link to regional or country articles to show information that wont fit in a global table)
Signage
Enforcement
Opposition

Softgrow 23:17, 6 February 2006 (UTC)

And let's not forget the excellent prior comment: "This article (like so many in Wikipedia), while interesting, omits any context of why & how speed limits developed... For instance, Br's Ref [sic] Flag Law, or New York's first limit, 1904...? "

As for urban limits: JzG is prolific about traffic calming in road safety.Duke Ganote 03:41, 9 February 2006 (UTC)

Now a "quick summary that wiki-links over to the [motorway subsection of the] Road Design section of Road Safety".Duke Ganote 13:26, 26 February 2006 (UTC)

Roads without speed limits photo

Is it possible to get a different photo for this section or failing that just remove the manipulated one that is currently in the article? I think that a manipulated photo has no place here. Softgrow 11:44, 16 February 2006 (UTC)

I agree. I removed it. :-) Now why don't you create your own true 140 MPH photo? Nova SS 15:39, 16 February 2006 (UTC)

Vandalism in progress - "push it to the limit"

Vandalism is in progress on this page and other pages under a lame meme called Safety Not Guaranteed. Affected pages include this one[4], limit [5], Limit (mathematics)[6], Limit of a function [7], etc. The vandal leaves a statement along the lines of "If you push it to the limit, safety is not guaranteed." Much unlike this meme, All your base are belong to us was actually funny. Nova SS 02:50, 17 February 2006 (UTC) (who pushes it to the limit all the time and somehow doesn't crash every time he drives)

Statistical basis for opposition

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 Ganote 02:11, 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. NFH 21:29, 5 March 2006 (UTC)

I've found the answer. Anonymous user:24.146.12.62 inexplicably changed almost all the equivalent values on 2 January 2005, rounding them to the nearest 5, thereby making them incorrect. See [8]. What's the easiest way to revert this very old edit (which could almost be called vandalism)? NFH 22:26, 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 SS 04:01, 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. NFH 07:18, 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 SS 16:19, 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. [9] 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: [10]. Nova SS 04:15, 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: [11] The anonymous user changed a large number of equivalents so they became incorrect. I'm not the one who needs glasses. NFH 07:39, 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 SS 14:56, 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 Ganote 15:57, 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.--Jusjih 14:12, 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. NFH 21:18, 7 March 2006 (UTC)
Support limits should be reported accurately and translation into alternative units likewise Softgrow 22:37, 7 March 2006 (UTC)
Support--Patrick 12:08, 8 March 2006 (UTC)
Oppose for the following reasons/truisms:
1. 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.
2. 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.
3. 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.
4. If ending with 5 or 0 is not accurate enough, why not carry out to decimal places? Where does it end?
Keep the 0 and 5 increments. Nova SS 04:11, 8 March 2006 (UTC)
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.--Jusjih 14:17, 3 May 2006 (UTC)
Support except drop the fraction down. To keep accuracy will ensuring people don't accidently get a speeding ticket driving thru a speed trap. Jon 18:12, 5 July 2006 (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. NFH 21:18, 7 March 2006 (UTC)
Oppose Softgrow 22:37, 7 March 2006 (UTC)
Support for mph speeds. Nova SS 04:11, 8 March 2006 (UTC)
Oppose--Patrick 12:08, 8 March 2006 (UTC)
Support for mph speeds. Duke Ganote 15:57, 1 April 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. Toiyabe 22:35, 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.--Jusjih 14:18, 3 May 2006 (UTC)
Oppose - 5 KM/H and 5 MPH rounding is inaccurcute; and likely to result in drivers falsely using this getting a speeding ticket driving thru a speed trap. Jon 18:11, 5 July 2006 (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. NFH 21:18, 7 March 2006 (UTC)
Oppose Softgrow 22:37, 7 March 2006 (UTC)
Support for kph speeds. Nova SS 04:11, 8 March 2006 (UTC)
Oppose--Patrick 12:08, 8 March 2006 (UTC)
Oppose If you look at the case for shared roadways in Australia, this is an almost 20% error. 58.165.14.146 15:08, 31 March 2006 (UTC) Dean
Oppose for both km/h and miles per hour.--Jusjih 14:19, 3 May 2006 (UTC)
Oppose for some reason as the 5 MPH / 10 KM/H. Jon 18:10, 5 July 2006 (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)".[12]

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.

Nova SS 03:40, 18 May 2006 (UTC)

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. Softgrow 07:56, 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 SS 13:59, 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. Softgrow 01:16, 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.

Nova SS 02:32, 19 May 2006 (UTC)

"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. --Kalmia 04:25, 22 August 2006 (UTC)

Even if you find a picture, that would be a highly unusual exception and not relevant to the discussion. Nova SS 13:42, 22 August 2006 (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. Toiyabe 23:26, 24 March 2006 (UTC)

You have some intriguing arguments. Would you mind expanding on this logic here? Nova SS 02:25, 25 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". Toiyabe 16:07, 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. [13]

Softgrow 21:59, 3 April 2006 (UTC)

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." Toiyabe 22:49, 3 April 2006 (UTC)

Chinese speed limit

I would like to request any citation for "on most roads, enforcement cameras are non-existent". I find at Wikitravel:Driving_in_China#Speed_Limits about photo radars, though I am unsure if they are common.--Jusjih 14:22, 3 May 2006 (UTC)

Badly in need of some major housekeeping...

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? --Doco 12:19, 21 May 2006 (UTC)

News

http://www.planetjh.com/flip_2006_05_03.html DyslexicEditor 03:14, 13 June 2006 (UTC)

Illegally slow limits?

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. --RedACE 19:56, 13 June 2006 (UTC)

Maybe you should check the speed trap article. Jon 18:18, 5 July 2006 (UTC)

85 Percentage Rule section obsolete

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. Jon 18:17, 5 July 2006 (UTC)

Please stop posting nonsense original research like this. Wikipedia is not a place to try out new theories. Nova SS 20:16, 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? LuNatic 06:30, 14 August 2006 (UTC)

I'll second that. Nova SS 13:57, 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 w 22:29, 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. --OliverH 08:58, 2 October 2006 (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 [14]. 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)

Suggestions? Alex Sims 09:58, 25 January 2007 (UTC)

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 concur with DeFacto. The situation is like that experienced by rural areas anywhere (see page 16 of footnote 6 of the main, that is, http://www.th.gov.bc.ca/publications/eng_publications/speed_review/Speed_Review_Report.pdf which discusses removing posted limited in remote areas...] Duke Ganote 14:43, 2 March 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 Sims 03:11, 3 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?