Measurement (defunct)
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Should this page's name be changed to "Kilometres per hour"? Vancouverguy 22:45, 17 Sep 2003 (UTC)

Yes it should, I'll change it now. WikiSlasher 03:57, 18 June 2006 (UTC)[reply]

Why has someone changed the spelling from kilometre to kilometer. Kilometre with the "tre" is the standard worldwide spelling only Americans spell it that funny way G-Man 23:00, 17 Sep 2003 (UTC)

No, in german it is also spelled de:Kilometer. --Thomas

It's not just German and American English. You only have to hover of the language box on the left of the article to see that it's "meter" in many languages. --Multiplexor (talk) 17:15, 25 April 2008 (UTC)[reply]

kph is a measurement of speed, not velocity

kph is a measurement of nothing. —Preceding unsigned comment added by 84.65.140.55 (talk) 13:06, 28 July 2009 (UTC)[reply]

In the metric SI system:

• k is a prefix "kilo" and represents a multiplier of 1,000
• p is a prefix "pico" and represents a multiplier of 1/1,000,000,000,000
• h is an accepted abbreviation for hour

Ignoring for the moment that it is not accepted practice to combine prefixes, the presumed literal interpretation of kph is: (1 hour/1,000,000,000) OR 3.6 microseconds.

As is currently, this section reads as an attempt to legitimize a misuse of the SI system. While sometimes this is seen, this does not make it an acceptable representation of kilometres per hour.

I therefore propose that this be amended to acknowledge that while kph is sometimes mistaken as the abbreviation for km/h, that the correct usage is, in fact, km/h and NOT kph (or, for that matter, kmph).

Enquire (talk) 04:44, 6 August 2011 (UTC)[reply]

I was under the impression that vectors require a direction. If so km/h could not be a vector, it would need to be 'x km/h, north' or something like that. I made an edit on that basis but it was reverted. Can this be clarified? Bobblewik  (talk) 4 July 2005 17:44 (UTC)

As the article force tells us, "A force can be represented by a vector with two properties: magnitude and direction." That doesn't mean that it would be wrong for it to say, as it does, that the "SI unit used to measure force is the newton," does it? Nor for newton to say that it "is the SI unit of force"?

Why in the world would you think that velocity would be any different? As its own article says:

• "It is thus a vector quantity with dimension length/time. In SI units this is metre per second."

Gene Nygaard 4 July 2005 18:20 (UTC)

I don't know the answer. The following seemed plausible:

The Difference Between Speed & Velocity
A scalar quantity is one which can be fully described by its size. Length, mass, temperature, energy, speed and volume are all scalar quantities. For example 20kg fully describes the mass of an object.
A vector quantity is one where you must also mention its direction. Force, velocity, displacement and acceleration are all vector quantities. For example a force of 20N can only be fully described by quoting its direction. 20N upwards will be different than 20N to the left.

Direction may be implicit in many cases, but if that source is correct, a vector quantity without a direction is incomplete. Bobblewik  (talk) 4 July 2005 22:07 (UTC)

At Knot (speed) someone changed 'm/h' to 'metres per hour' because it looked too much like 'miles per hour'. That's fine with me, but I was wondering. Isn't that usually written as mph? Which would solve the ambiguity. And is 'm/h' an acceptable notation for 'metres per hour'? I suppose it is because in the metric system you can combine anything with anything. Although km/h and m/s are more common. DirkvdM 09:19, 15 September 2005 (UTC)[reply]

You are right. The unit 'metres per hour' is correctly written as 'm/h'. The SI website clearly lists the:

• official symbol for 'metre'

and the

• official symbol for 'hour'. Note that the SI unit of time is the second, not the hour. The hour just happens to be 'accepted for use' with SI units.

As you might expect, the Wikipedia articles Metre and Hour repeat the official symbol. So there is no reasonable ambiguity with 'm/h' and it is incorrect to claim that there is.

There are no internationally agreed symbols for 'miles per hour' so I cannot advise you on that. Note also that 'mph' is language dependent. One of the benefits of the metric system is that it does not depend on knowing the language, just as the international symbol for mercury is Hg. For example, 'miles per hour' and 'kilometres per hour' would be 'mao' and 'cao' in Italian.

However, Wikipedia articles appear to accept 'mi/h' and 'mph' as forms for miles per hour. I think I have also seen 'mi/h' on speedometers. Either of those abbreviations work for me. Bobblewik 16:03, 24 September 2005 (UTC)[reply]

Just because the official symbol for meters is m, and the symbol for hours (at least when used with SI) is h, that would only show that m/h can mean meters per hour, not that it cannot mean miles per hour. Good grief, even among the SI and units acceptable for use with it, we have the symbol 'rad' which can stand for two different units, rad and rad. We also have "nm" used for nautical miles, as well as the SI unit of lenghth, nanometers.

For miles per hour, mi/h is better than mph, IMHO.

But you will almost never see m/h used for miles per hour in current usage, so there is no real ambiguity. For that matter, you are probably even less likely to run into meters per hour in actual usage. So enough of this tilting at windmills. Gene Nygaard 17:17, 24 September 2005 (UTC)[reply]

I suppose the '1852 metres per hour' in the article really should be changed to '1,852 km/h'. There is no need to use the uncommon 'metres per hour'. Also notice my use of a comma. I read in one thread that the SI rules say you can use either a comma or dot here (and the thousands-separator is a space). But don't worry, I'll use a dot :) .

As for something like km/h being the same in all languages. That is alas not entirely true. Prefixes like 'kilo' are. And afaIk the same goes for the 'm' in all western languages, because the equivalents of 'metre' all happen to start with an 'm' (which isn't a total coincidence of course). But the 'h' isn't universal. It works in Spanish (hora) and French (heure) and I imagine in all Latin languages. But not in Dutch, where the word for 'hour' is 'uur', so it's 'km/u'. which made me wonder about German, inwhich the word for 'hour' is 'Stunde'. Which rather inconveniently starts with an 'S' (capital, but still). So I looked up the German article on km/h and it turns out they write it with an 'h'. Well, they had little choice. But then I looked up the same article in Dutch and there it is also written as km/h. Which surprises me, because most people (though not all) use km/u, even including me, and I am a very strong supporter of standardisation. I'll amend my ways forthwith :) . This however seems to be the only problem with SI base units (in western languages and as far as I know). 'Gram' starts with a 'g' in all languages, as does does 'second' with an 's'. And the others (A, K, mol, cd) seem to be too recent to have different names in different languages.

I also Googled this. In Dutch pages km/u is just a little more common than km/h. I can't make a comparison for German because I wouldn't know what to test against, but km/h scores close to 2 million hits. So at least it's common. DirkvdM 07:26, 26 September 2005 (UTC)[reply]

I am really supriced that the Dutch would have any ambiguity about this! The km/h is the international standard and the individual abrivitions don't come from the language of the particular country. F.ex. in Finland hour is "tunti", still kilometriä tunnissa is km/h as per SI (which itself stands for "Kansainvälinen yksikköjärjestelmä" in Finnish as in English although its a French acronym), day, "päivä" is d, year, "vuosi" is a and so forth, like in (scientific) English. And I assume the prefix "micro" is abrevieded with the Greek letter mu (μ) in Dutch too?82.181.150.151 21:42, 13 February 2007 (UTC)[reply]

I was under the impression that residential areas are usually 20 or 25 mph, or about 30 or 40 km/h. Are they actually 50 km/h in metric countries? 50 km/h (about 30 mph) is a bit fast for a neighbourhood... koolman2 08:34, 30 September 2005 (UTC)[reply]

In the UK residential limits are 30mph. In Australia residential limits are 50km/h (though 40km/h limits apply past schools during certain posted hours). YMMV! Graham 09:03, 30 September 2005 (UTC)[reply]

Interesting! Thanks- koolman2 18:38, 30 September 2005 (UTC)[reply]

Traffic accident research shows that the risk of death resulting from a pedestrian being hit by a vehicle rises dramatically (five times) when comparing an impact at 50 km/h (31.25 mph) to 30km/h (18.75 mph). In other words, the risk of death or major injury at 30 km/h (say, 20 mph) compared to 50 km/h (say, 30 mph) is 20% or one fifth). See, for example:

• Rosén, Erik; Sander, Ulrich. "Pedestrian fatality risk as a function of car impact speed" (PDF). Accident Analysis and Prevention. Autoliv Research, Wallentinsvägen 22, 447 83, Vårgårda, Sweden. pp. 536–542. {{cite web}}: Cite has empty unknown parameter: |coauthors= (help); External link in |work= (help); More than one of |work= and |journal= specified (help)

As a result, various municipalities around the world are experimenting with and/or implementing reduced speed limits for residential and./or school zones.

Enquire (talk) 20:40, 7 August 2011 (UTC)[reply]

Germany (or at any rate Frankfurt) tends to use 50 km/h is normal urban areas, but 30 km/h is residential roads that are nor designed for through traffic. Martinvl (talk) 06:44, 8 August 2011 (UTC)[reply]

What the speed 50 km/h looks like on a normal bicycle

Does anyone else think that this is not really necessary. Firstly, what it looks like on the photo despends on the shutter speed of the camera. If the shutter speed is different, then the image would look very different too.

Also, does the image add any meaning to the article? Is it easier to picture what km/h means? Richard B 18:24, 18 December 2005 (UTC)[reply]

I agree, the image is worthless. Removed as per WP:BB Graham 11:08, 19 December 2005 (UTC)[reply]

The link that you currently have in your article points to a site that is an unauthorized copy of the other site. The original page of online speed conversion is http://www.convert-me.com/en/convert/speed The site http://www.convert-me.com/ exists for years (you can check http://www.archive.org) and the illegal copy linked from this article was only placed recently. As the owner of the original www.convert-me.com project, I'll be happy to provide any additional information and proofs of authenticity. My name is Sergey Gershtein and my contact info can be found on http://sergey.gershtein.net/ I think I will go ahead and edit the page changing the link to make it point to the original site.

Also the other link is a broken one.

Is it really wrong? http://www.thefreedictionary.com/kph http://dictionary.reference.com/browse/kph http://webster.com/cgi-bin/dictionary?va=kph http://www.google.com/search?q=kph

All say kph is kilometers per hour.

No, it's not wrong. Following standard practice for abbreviations, kilometres per hour = kph; if the standard abbreviation, km, is instead used for kilometres, then kilometres per hour becomes kmph; these are perfectly valid abbreviations. Unfortunately, an editor has, at some point, labelled them as incorrect because they are not the accepted standard abbreviations used in scientific discourse. (Just to be clear, this is not an anti-science comment; I am a scientist who uses kmh^-1.) However, not being part of a standard does not make something incorrect—if it did we'd all be using metres per second anyway. ObfuscatePenguin 18:23, 20 September 2007 (UTC)[reply]

It depends exactly what your definition of "wrong" is; one can argue that no misspelling etc is "wrong", just "non-standard". However for practical purposes, "non-standard" equals "wrong". Certainly no high quality publication (ie not the Metro or other error-filled rags) would regard "kph" as acceptable. —Preceding unsigned comment added by 89.240.52.217 (talk) 20:34, 12 April 2011 (UTC)[reply]

I have never seen "kph" on a car's speedometer - as explained in the article, "kph" is specifically an English abbreviation, not an internationally accepted symbol whereas "km/h" is used internationally. Martinvl (talk) 06:53, 13 April 2011 (UTC)[reply]

I've moved the discussion to Wikipedia talk:Naming conventions#RfC: Should titles of article on units of the form "X per Y" be singular or plural?; the two of us (myself & User:Piercetheorganist) could have this discussion forever, and get nowhere fast. Hopefully, more people have that page on their watchlist, and will contribute. Oli Filth^(talk) 13:59, 6 January 2008 (UTC)[reply]

I would add an wiki online convertion page (to change from km/h to mph and viceversa).

Something similar to :

but applied to conversions :

<inputbox> type=? width=24 break=no buttonlabel=km/h to mph </inputbox>

Is there a standard on Wikipedia for which side of the equation the page's subject should be on? The section here lists km/h on different sides for different lines, which is confusing. 205.167.180.131 (talk) 17:35, 25 June 2009 (UTC)[reply]

The article states "the official recommendation from the BIPM is to use km/h" (km/h in italics). The use of italics here is unfortunate. The BIPM specifically states: "Unit symbols are printed in roman (upright) type regardless of the type used in the surrounding text" http://www.bipm.org/en/si/si_brochure/chapter5/5-1.html — Preceding unsigned comment added by 81.142.49.137 (talk) 14:17, 15 August 2011 (UTC)[reply]

De-italicised "km/h" as per suggestion — Preceding unsigned comment added by 92.13.17.54 (talk) 18:56, 27 August 2011 (UTC)[reply]

I think we should remove these. We already have interwiki links for many languages and having a translation for a dozen random ones doesn't add to the article. It is a weird criteria:

• The following are translations of the text "kilometres per hour" where either "km" or "h" do not appear in the text.

as well. - SimonLyall (talk) 19:43, 11 April 2012 (UTC)[reply]