User:Garamond Lethe/sandbox/kmh

A Bit of Background
There's a wonderfully strange dispute going on over how this article should be written. The existing version treats "km/h" as kilometre per hour / kilometer per hour and then describes the two standard unit symbols. However, the name of the article is not "kilometre per hour", but "km/h". The latter string has a history intertwined with (but distinct from) "kilometre per hour": "km/h" is one of several abbreviations used before (and after) international standardization occurred, and standardization has created a body of rules by which "km/h" must be constructed and represented (down to specifying how the [solidus] may and may not be used and the requirement of an upright Roman typeface).

This distinction (so far unspoken, to the best of my knowledge) has resulted in a bifurcation of the focus of the article. For example, the European Union may have adopted the units "kilometers per hour" to be used in specific areas, but that would more properly be noted in an article on "kilometers per hour", not "km/h". Pointing out that existing dictionaries continue to treat "km/h" as an abbreviation instead of a symbol has very little to do with the definition and standardization of "kilometers per hour", but is a useful and interesting datapoint in the evolution of "km/h".

Elsewhere I had proposed that the article be split in two: km/h (Unit Symbol) and km/h (pre- and non-SI uses). A more natural split might be kilometers per hour and km/h. While I think both can find a home within one article, it may helpful to editors to remind them that there are two distinct concepts in play. Garamond Lethe 16:50, 12 July 2012 (UTC)

RFC
At least one editor would like to resolve the focus problem using RFC. I'll be starting a draft of that here.

Use of kph in the EU
User:Garamond Lethe/sandbox/kph

Current Lead
The kilometre per hour (American English: kilometer per hour) (unit symbol km/h or km·h−1) is a unit of speed, expressing the number of kilometres travelled in one hour.

Lead
km/h is one of several abbreviations for and one of two standard symbols of the unit of speed "kilometers per hour".

Compromise lead
The kilometre per hour (American English: kilometer per hour) (unit of speed, expressing the number of kilometres travelled in one hour. English-language abbreviations in current use include "km/h", "kmph" and "km/hr".

km/h as an abbreviation
Although the unit of length kilometer first made its appearance in English in 1810, the compound unit of speed "kilometers per hour" was first observed no later than 1866. "Kilometers per hour" did not begin to be abbreviated in print until many years later, with several different abbreviations existing near-contemporaneously.


 * 1889: "k. p. h."
 * 1895: "km:h"
 * 1898: "km/h"
 * 1899: "km./hr."
 * 1899: "km./hr"
 * 1900: "km/hr."
 * 1902 "k.p.h."
 * 1911: "K.P.H."
 * 1912: "K. P. H."
 * 1914 "km. hr."
 * 1915: "km/hour"
 * 1915: "km.-hr."
 * 1916: "km. per hour"
 * 1919: "km/hr"
 * 1921: "K.p.h"
 * 1933: "KPH"

Current accepted abbreviations are listed below. Note that some of these abbreviations may be limited in scope to specific domains, such as the United State military.


 * "km/h"


 * "kmph"


 * "kph"


 * "KMHR"


 * "KPH"

km/h as a symbol
A desire for standarization of weights and measures across international borders led to the creation of the General Conference on Weights and Measures (CGPM) whose first conference in 1889 sanctioned international prototypes for the meter and the kilogram. In 1927, the seventh CGPM conference further refined the definition of the meter and, with the seventh resolution of the 9th conference (1948) several symbols were associated with units, including the symbol m for meter and h for hour. The 11th conference of the CGPM (1960) selected six units, including the meter, to be considered as an International System of Units (SI) along with a standarized set of prefixes and their corresponding symbols (including kilo (k) for a multiplying factor of 1000). Note that while the second was defined as the base unit of time during this process, the hour was not defined as either a base unit or supplemental unit and is defined instead as a Unit in use with the International System along with minute and day. There are two methods for indicating a compound unit is the quotient of two or more units. A solidus may separate the units, thus producing km/h, or a negative exponent may be used along with either a space or a dot between units, thus $km h^{-1}$. Note that conformance to the standard requires use of a Roman (upright) font. The symbol must not be changed to indicate a plural and no space should be left between a unit symbol and its prefix.

The SI explicitly states that unit symbols are not abbreviations and are to be written using a very specific set of rules. M. Danloux-Dumesnils provides the following justification for this distinction:

"It has already been stated that, according to Maxwell, when we write down the result of a measurement, the numerical value multiplies the unit. Hence the name of the unit can be replaced by a kind of algebraic symbol, which is shorter and easier to use in formulae. This symbol is not merely an abbreviation but a symbol which, like chemical symbols, must be used in a precise and prescribed manner."

Regulatory use of km/h
In 1988 the United States National Highway Traffic Safety Administration promulgated a rule stating that "MPH and/or km/h" were to be used in speedometer displays. On May 15, 2000 this was clarified to read "MPH, or MPH and km/h". However, the Federal Motor Vehicle Safety Standard number 101 ("Controls and Displays") allows "any combination of upper- and lowercase letters" to represent the units.

EU directive 75/443/EEC which regulates the layout of speedometers within the European Union, uses the text "km/h" in all languages.