Talk:Speed limit/Archive 1

Crash vs. Accident
This is a stub for a discussion of the terminology of crash vs. accident. Please discuss here before further edits. User:Novasource

Note that it is my opinion that "crash" is the correct terminology. The original poster, 66.25.47.88, is correct in that government agencies, including the NHTSA and Federal Highway Administration (a clearly pro-highways agency, unlike the NHTSA which sometimes appears to be in cahoots with anti-highway forces and insurance industry), are preferring the term crash over accident. "Accident" makes a judgment because it implies an unpreventable crash, whereas "crash" includes both preventable and unpreventable crashes. User:Novasource


 * Okay. Provided the main article describes "crash" as a superset of "accident," I will drop my objection. --24.107.227.12 16:33, 6 August 2005 (UTC)


 * Thanks. I am sure that the distinction and commentary on crash vs. accident would be great. Only question is whether. Speed Limit is the right place? Would other places work? 66.25.47.88 21:27, 6 August 2005 (UTC)


 * Speed limit is one place, but perhaps an ideal place would be an article about car crashes, including politics, crash forces, safety, insurance, etc. What do you think? --24.107.227.12 22:51, 10 August 2005 (UTC)


 * That sounds like a great idea. Could you start the article? Novasource 14:05, 11 August 2005 (UTC)

Merge with 30 mph
I've done a preliminary merge of the two pages, as indicated in the article. Comment and modify to your heart's desire. Josh 05:22, Apr 13, 2005 (UTC)

Where is Canada's speed limit?
Each province in Canada has its own speed limit laws. Most provinces have a speed limit on freeways of 110km/h except for Ontario and Quebec which have freeways (and toll highways) at 100km/h. Also rural two-lane roads in Canada have a speed limit of 100km/h (as is standard also in Europe and Australia) but in Ontario and Quebec it is only 80-km/h and 90km/h in rural northern areas. Generally Ontario and Quebec have the lowest speed limits not just in Canada, but in North America. I feel that the Paragraphs in the Article on Canadian Speed Limits is best under the circumstances.

What's an example of a rural two-lane road in Canada with a speed limit of 100 km/h? -rak

Most rural two-lane roads in Alberta, Saskatchewan, and Manitoba are signed at 100km/h. Many but not all rural two-lane highways in B.C. are also signed at 100km/h. I know for a fact it is the default two-lane rural speed limit in Alberta and most rural highways are signed at 100km/h.

Mph in US and UK only?
Am I right every country in the world uses Kph speed limits except the US and the UK? if so, this article should probably say this interesting fact more clearly. Seabhcán 00:50, 8 Jan 2005 (UTC)

Nobody uses "Kph." They use kilometres per hour whose legal symbol is "km/h". SI units do not have abbreviations, they use symbols that do not vary with language or type.


 * Hold your horses there, there's another 12 days to go until us Irish finally change our speed limits to km/h (or kph as the signs will say)! zoney &#09827; talk 13:35, 8 Jan 2005 (UTC)

The conversion is complete and the signs show km/h not kph. Kph is wrong, wrong, wrong!!!


 * There may be a few others, but I can't think of them. The US, in fact, doesn't use metric for anything!

Incorrect. 40 % of US industry is metric. Automobile manufacturing is the most visible. With some industries using metric parts and others not, it creates an added cost burden to Americans who have to maintain duplicate inventories of parts to serve both sides.


 * To make it easier to convert in the real world, the converted speeds here should be listed as follows:


 * Metric to Imperial: 10 = 5, 20 = 10, 30 = 20, 40 = 25, 50 = 30, 60 = 40, 70 = 45, 80 = 50, 90 = 55, 100 = 65, 110 = 70, 120 = 75, 130 = 80, 140 = 90, 150 = 95.


 * Imperial to Metric: 5 = 10, 10 = 20, 15 = 25, 20 = 30, 25 = 40, 30 = 50, 35 = 55 (or 60), 40 = 60, 45 = 70, 50 = 80, 55 = 90, 60 = 95 (or 100), 65 = 100, 70 = 110, 75 = 120, 80 = 130, 85 = 140. 24.146.12.62 03:15, 11 Jan 2005


 * The UK (Where I live) also rarely uses Metric. Milk still comes in pint and two pint bottles, which, due to EU law, are labled as "1.136 l"! Seabhcán 15:13, 11 Jan 2005 (UTC)
 * I just read in Pint that "The UK pint is officially defined as 0.56826125 litres precisely". So whats the point of using it, if its defined in terms of litres anyway??? Seabhcán 15:16, 11 Jan 2005 (UTC)

UK industry is fully metric as are the majority of prepackaged goods in the shops. Weather is predominately reported in metric, petrol and oil are sold in litres, length products are sold by the metre and most shops use kilogram scales when selling produce to customers, etc. Some milk is sold in litres, others in pints, but the remaining non-metric products compose a remnant not the norm


 * convenience, and especially tradition. The convenience because there are lots of bottles, etc, made in this size, and also because they are frequently very nicely sized units. Thryduulf 16:36, 11 Jan 2005 (UTC)
 * Maybe, but when I buy a half litre of milk in Ireland, I don't notice the missing 0.06826125 litres. Personal preference I suppose. ;-) Seabhcán 20:47, 11 Jan 2005 (UTC)

It is what you want to be use to. In Australia milk is sold in 600 mL and 1200 mL sizes. Thus you get 32 mL and 64 mL more. The UK can do the same. BTW, why dis you say "missing 0.06826125 litres", instead of saying "missing 68 mL"? Maybe in imperial that type of nonsense works because imperial doesn't employ user friendly prefixes to scale numbers, but metric does. Maybe you and other luddites might find metric more convenient if you took advantage of its user friendliness instead of trying to incorporate bad imperial practices when using metric. 17:01, 30 Jan 2005 Ametrica


 * Touché. :-) Seabhcán 20:38, 30 Jan 2005 (UTC)

Interesting. When I visited England more than 20 years ago, the signs were all in metric. Did anything change? Or does Northern Ireland still use the traditional system of measurement? 64.50.192.206 14:11, 31 July 2005 (UTC)

Proposed reorganisation of article
I think the current layout of the article is a little hap-hazard - without a good logical structure. I propose a reorganisation here: Speed limit/proposed, along with some new sections which need to be writen, such as a proper history section (Speed limits must be a 20th Century invention? Were there limits before the automobile?) and Speed limit enforcement, which must vary greatly from country to country. We're also missing info on many regions of the world, such as Central and South America, Africa, and Russia. What do you think? Seabhcán 01:39, 21 Jan 2005 (UTC)


 * First thing to do is to throw "kph" out of your vocabulary. Gene Nygaard 01:48, 21 Jan 2005 (UTC)


 * Why? Its perfectly understandable, and serves as a link to the correct article: Kph. Seabhcán 12:03, 21 Jan 2005 (UTC)


 * Although I prefer km/h, it doens't really matter to me which is used. However, you should pick one and use it consistently, not mix and match. Thryduulf 12:34, 21 Jan 2005 (UTC)


 * Wrong. That Kph merely redirects to Kilometre per hour (do slashes work in article names and Wikipedia search engine?), and if you had clicked on that link, you would have learned what the proper symbols are.  Even in the United States, our speedometers don't say "kph"&mdash;they use the proper "km/h". Gene Nygaard 13:18, 21 Jan 2005 (UTC)
 * km/h redirects to Kilometre per hour, so yes it does work in the article name and search engine. Thryduulf 13:26, 21 Jan 2005 (UTC)


 * For what it's worth, km/h is the abbreviation used on our spanking new metric speed limit signs in Ireland. zoney &#09827; talk 13:29, 21 Jan 2005 (UTC)


 * By the way, if you are worried about parallelism, "mi/h" is acceptable, and redirects to Miles per hour (for some reason that one is plural, probably from before preference for singular expressed). Lots of latitude there; English units are like old software, no longer supported and updated--nobody really making any rules for them any more. Gene Nygaard 13:31, 21 Jan 2005 (UTC)


 * I've made several edits and comments on the /proposed page, along with a couple of typo and spelling fixes. Thryduulf 13:11, 21 Jan 2005 (UTC)


 * I'm happy with replacing all "kph" with "km/h". Seabhcán 17:04, 21 Jan 2005 (UTC)

"Forces increase exponentially"
Yesterday, I removed the word "exponentially" from the claim that "crash forces increase exponentially as speed increases." Today, Coolcaesar reverted my deletion with the note "Looks like Coneslayer wasn't paying attention in high school physics!" I would like to point out that I hold a B.S. in physics, in addition to a Ph.D. in astrophysics. I will therefore use this space to explain my deletion.

First, understand what is meant by "exponentially." If a force increases exponentially with speed, we're saying: $$F \propto {\rm e}^v$$. So let's see if that's the case. The original statement is a bit vague, but let's say it's referring to the average deceleration force, which occurs over a fixed distance $$d$$ travelled (e.g. the crush zone of the car). We will assume constant deceleration during this interval.

We have then that the car decelerates from an initial velocity $$v_0$$ over a distance $$d$$ at a constant acceleration $$a$$. From basic mechanics, $$x=at^2 + v_0 t$$ (taking $$x(t=0) = 0$$). Now, the end-state occurs when $$v=0$$, also at which time $$x=d$$. This is when $$v_0 = at_{final}$$, or $$t_{final}=v_0/a$$. Substituting, we have $$d=at_{final}^2 + v_0 t_{final}$$, or $$d=a(v_0/a)^2 + v_0(v_0/a)$$, or finally $$d=2v_0^2/a$$ and hence $$a = 2v_0^2/d$$

Thus, the deceleration (and hence force, since the car's mass is constant) increases with the square of the initial speed. It does not increase exponentially.

You may be able to get different dependences with different assumptions, such as a fixed time, instead of distance, over which the deceleration occurs, but I don't see how to get an exponential dependence, with any reasonable choice of assumptions. If you can, please feel free to illustrate, but don't just point us to the force and acceleration articles, like you did in your edit. -- Coneslayer 22:11, 2005 Mar 24 (UTC)

Oops! Okay, I concede you have analyzed the underlying mathematics quite clearly. I was using exponential (and I believe whomever originally inserted that word also meant the same) in the sense that the relationship is not a simple first-degree or linear function, which is the most intuitive relationship for most people. That is, neither F nor a equals v times some constant.

Of course, having reread several Wikipedia articles on algebra to refresh my own memory, I also concede that exponential is inappropriate since v itself is not the exponent. Perhaps "nonlinear" may be more appropriate. --Coolcaesar 02:00, 25 Mar 2005 (UTC)

Actually, "quadratically" would be most appropriate. --yermo 06:13, 26 Mar 2005 (UTC)

I also immeidately recognized that the use of "exponentially" as incorrect. However, I did NOT see it in the WikiPaedia article (since I read the article after the correction was made). I saw it used incorrectly in the article that was referenced. That must be how it ended up in WikiPaedia. It was used it to describe to the rate of increase in two things relatvie to speed: 1. probability of injury and 2. severity of injury. However, I think they gave no emperical evidence for either claim. They should have posed the claims as an interesting challenge to anybody who wishes to refine and extend the research. Either claim might be true. -dw

US Speed Limits
I will post a US State by State highway speed limit chart. I will also credit the list to the site I found it on, and I hope people occasionally update the chart from time to time.

i replaced the canadian speed limit sign example. the new image is better quality and it is a better example. I hope thats okay. bjj

Mexico speed limits?
Does anyone know what the speed limit is on various classes of roads in the country of Mexico?

85th Percentile Speed
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Is this true? If speed limits were set to the 85th percentile of drivers, then that would mean setting a speed limit would actually raise the average speed at which people take a road, since (at least in the United States) many more than 15% of drivers are speeding at a given time, and most feel compelled to be doing at least the speed limit. In practice (this is just anecdotal observation) the average seems to be 5 to 7 mph over the speed limit, and I'd guess 85th percentile's about +10-15. 137.22.11.145 04:22, 1 Apr 2004 (UTC)

Yes, it's true. Worldwide studies on driver reaction to speed limits go both ways, but many United States studies show little or no clear relationship between actual speeds and speed limits except that 85th percentile speed limits can affect speed dispersion. The prevailing theory is that speed dispersion (i.e., speed difference between fastest and slowest drivers) is reduced with 85th percentile limits, but empirical evidence of this is spotty.

Europe in-town speed limits
What about in-town speed limits in Europe? AFAIK, it's 50 km/h in most countries, often 30 km/h in residential areas, sometimes even only 20 km/h. Switzerland changed from a general in-town limit of 60 km/h to 50 km/h in 1984, just as it did switch from 100km/h outside towns to 80 km/h and from 130 km/h on highways to 120 km/h in 1985. Also, isn't there a minimum speed a car must be able to attain if it is to be driven on a highway (Autobahnen, Autostrade, Autoroutes) in many European countries? I thought it was 60 km/h... Lupo 14:57, August 8, 2005 (UTC)

American vs. British English
I have reverted this article to American English from a recent conversion to British English. Per the |National varieties of English clause of the Wikipedia Manual of Style: "If an article is predominantly written in one type of English, aim to conform to that type rather than provoking conflict by changing to another."

This article is predominantly American English, and American subjects are by far the largest in the article, so let's keep American English.

By the way, "Interstate" is a proper noun when referring to the US Interstate Highway system, so it is correc to capitalize it. Novasource 17:05, 8 August 2005 (UTC)

Safety
This section needs to be reworked. Much of it is opinion and partially thought out theories. There is some good info here, but it needs to be extracted and the whole section rewritten.


 * I agree. Do you have any thoughts on how to do this? Novasource 21:56, 12 August 2005 (UTC)

Perhaps requiring sources for some of the theories presented. Also, simply eliminating some of the wordiness might help. I can try and pare it down, let me know how it looks after. 17 August 2005


 * Changed it, and moved some things to a new category--enforcement.

POV deletions
I just deleted everything contributed by 83.196.194.166. Virtually everything this person wrote was POV, completely uncited, or or made logical errors like a hasty generalization (e.g., the implication that heresay from one radiology unit of a hospital has broad meaning on a country's entire road system).

The person is invited to recontribute without POV and with better documentation. I feel that the speed limit article has benefited from many recent improvements in citations, and I don't want to loose this through unsubstantiated commentary.

Novasource 22:12, 23 September 2005 (UTC)


 * I concur with Novasource's reasoning.--Coolcaesar 04:26, 24 September 2005 (UTC)


 * The same guy did it again, anonymously. I found grammar and spelling erorrs, plus even more POV information. Whoever you are, please provide citations for your quotes. Also, please consider working on it over here in the Discussion page before you post it. Thanks, Novasource 02:15, 26 September 2005 (UTC)


 * What you are doing here, Novasource, is not good at all. You have deleted article content together with supported references, including The UK Transport Research Laboratories. In your edit comment, you are describing it as spam.


 * Furthermore, the impression I get from reading the page as is, is that it is has a degree of POV, toning down the importance of speed as a problem. See especially the Safety and Enforcement sections, as well as the External links (which begins with two links to Association of British Drivers, which is highly POV). Novasource actions maintains that POV. The content added by this anon seems to be valid counterpoints to what was claimed in the article. The claims were, at least for the most part, supported by the references that Novasource deleted. The amount of grammar and spelling errors, were certainly not enough to exclude this content. -- Egil 06:54, 26 September 2005 (UTC)


 * I added an introduction to safety that aims to be more NPOV, and also summarize findings of various studies. I also removed much of the Isle of Man material. There seems to be a conflict between the income brought to the island due to 'speed tourism' and the problem with road safety, but more references are required to cover it properly. -- Egil 08:08, 26 September 2005 (UTC)

Utah
I live in Utah, and it seems like everyone goes exactly 9 mph over the speed limit, no matter what kind of road. the only exception are school zones when the lights are flashing. and whats more, the cops never pull anyone over, and in fact they usually go 9 over. so if thte limit is 55, more than half of the people on the road go 64, and the police could care less. but go 10 over, and they are on your case so fast. you don't fail your driving test in utah if you go + or - 9 mph, but go + or - 10 over, and you'll fail. i think the police follow that principle or something. what do you think? Vandalism destroyer (talk) 05:49, 9 April 2008 (UTC)

New Zealand
certain highways in central Auckland have had a new limit of 80km/h applied, whereas the majority are at 100 km/h. I will figure out exactly which ones and update the main page. If anyone else knows the areas where the new limit applies, feel free to update the page. One area is On State Hwy 1 north of Warkworth (In the "Dome Valley") the open road limit is now 80kmh.

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 for this reason, but were added again under the claim Photographs are not POV. . 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)

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 &mdash; it is rare, for example, for someone to be given a speeding ticket for driving 70 mph on a road posted at 65 &mdash; 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). 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 Softgrow 23:17, 6 February 2006 (UTC)
 * 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

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)