Kilometres per hour

History

Although the metre was formally defined in 1799, the term "kilometres per hour" did not come into immediate use – the myriametre (10,000 metres) and myriametre per hour were preferred to kilometres and kilometres per hour. In 1802 the term "myriamètres par heure" appeared in French literature. The Dutch on the other hand adopted the kilometre in 1817 but gave it the local name of the mijl (Dutch mile).{{cite book |url=https://archive.org/details/allereerstegron00ramagoog |title=Allereerste Gronden der Cijferkunst |first=Jacob |last=de Gelder |location='s-Gravenhage and Amsterdam |language=nl |year=1824

Notation history

The SI representations, classified as symbols, are "km/h", "km h−1" and "km·h−1". Several other abbreviations of "kilometres per hour" have been used since the term was introduced and many are still in use today; for example, dictionaries list "kph", "kmph" and "km/hr" as English abbreviations. While these forms remain widely used, the International Bureau of Weights and Measures uses "km/h" in describing the definition and use of the International System of Units. The entries for "kph" and "kmph" in the Oxford Advanced Learner's Dictionary state that "the correct scientific unit is km/h and this is the generally preferred form".

Abbreviations

Abbreviations for "kilometres per hour" did not appear in the English language until the late nineteenth century.

The kilometre, a unit of length, first appeared in English in 1810, and the compound unit of speed "kilometers per hour" was in use in the US by 1866. "Kilometres 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."
• 1900: "kms./hr."
• 1902: "k.m.p.h."
• 1903: "KMph."
• 1910: "km ph"
• 1911: "K.P.H."
• 1914: "km. hr."
• 1915: "km/hour"
• 1915: "km.-hr."
• 1916: "km. per hour"
• 1921: "kms/hr."
• 1922: "Kmph"
• 1927: "kmph."
• 1933: "KPH"
• 1939: "kmph"
• 1940: "KMPH"

With no central authority to dictate the rules for abbreviations, various publishing houses and standards bodies have their own rules that dictate whether to use upper-case letters, lower-case letters, periods and so on, reflecting both changes in fashion and the image of the publishing house concerned, In contrast to the "symbols" designated for use with the SI system, news organisations such as Reuters and The Economist require "kph".

In informal Australian usage, km/h is more commonly pronounced "kays" or "kays an hour". In military usage, "klicks" is used, though written as km/h.

Unit symbols

In 1879, four years after the signing of the Treaty of the Metre, the International Committee for Weights and Measures (CIPM) proposed a range of symbols for the various metric units then under the auspices of the General Conference on Weights and Measures (CGPM). Among these were the use of the symbol "km" for "kilometre".

In 1948, as part of its preparatory work for the SI, the CGPM adopted symbols for many units of measure that did not have universally agreed symbols, one of which was the symbol "h" for "hours". At the same time the CGPM formalised the rules for combining units quotients could be written in one of three formats resulting in "km/h", "km h−1" and "km·h−1" being valid representations of "kilometres per hour". The SI standards, which were MKS-based rather than CGS-based, were published in 1960 and have since then have been adopted by many authorities around the globe including academic publishers and legal authorities.

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

SI, and hence the use of "km/h" (or "km h−1" or "km·h−1") has now been adopted around the world in many areas related to health and safety and in metrology in addition to the SI unit metres per second ("m/s", "m s−1" or "m·s−1"). SI is also the preferred system of measure in academia and in education.

Non-SI abbreviations in official use

• km/j or km/jam (Indonesia and Malaysia)
• km/t or km/tim (Norway, Denmark and Sweden; also use km/h)
• kmph (Sri Lanka and India)
• กม./ชม. (Thailand; also uses km/hr)
• كم/س or كم/ساعة (Arabic-speaking countries, also use km/h)
• קמ"ש (Israel)
• км/ч (Russia and Belarus in a Russian-language context)
• км/г (Belarus in a Belarusian-language context)
• км/год (Ukraine)
• km/st (Azerbaijan)
• km/godz (Poland)

Regulatory use

]] During the early years of the motor car, each country developed its own system of road signs. In 1968 the Vienna Convention on Road Signs and Signals was drawn up under the auspices of the United Nations Economic and Social Council to harmonise road signs across the world. Many countries have since signed the convention and adopted its proposals. Speed limits signs that are either directly authorised by the convention or have been influenced by the convention are shown below:

File:Hungary road sign C-033-100.svg|100 km/h sign following the most common implementation of the Vienna Convention style (Hungary) File:Sweden road sign C31-3.svg|Swedish 30 km/h speed limit – the yellow background provides a contrast in case snow covers the background against which one perceives the road sign. File:IE road sign RUS-043.svg|Since the text "km/h" on this Irish speed limit sign is a symbol, not an abbreviation, it represents both "kilometres per hour" (English) and "ciliméadar san uair" (Irish) File:AE road sign 344-60 (Type II).svg|60 km/h speed limit in Arabic numerals (below) and Arabic script (above) (UAE) File:Vesiliikennemerkki 11.svg|Waterways speed limit of 9 km/h (Finland) File:Samoa - Speed Limit.svg|Samoa uses both miles per hour and kilometres per hour File:MX road sign SR-9 (50).svg|50 km/h sign in Mexico File:NO road sign 812.40.svg|Advisory 50 km/h sign in Norway File:Sweden road sign E11-5.svg|Advisory 50 km/h sign in Sweden

In 1972 the EU published a directive (overhauled in 1979 to take British and Irish interests into account) that required member states to abandon CGS-based units in favour of SI. The use of SI implicitly required that member states use "km/h" as the shorthand for "kilometres per hour" on officialUntil 2010, the directive covered "economic, public health, public safety or administrative purposes"; since then of the EU internal market. documents.

Another EU directive, published in 1975, regulates the layout of speedometers within the European Union, and requires the text "km/h" in all languages, even where that is not the natural abbreviation for the local version of "kilometres per hour". Examples include:

• Dutch: "kilometer per uur" ("hour" is "uur" – does not start with "h"),
• Portuguese: "quilómetro por hora" ("kilometre" is "quilómetro" – does not start with "k")
• Irish: "ciliméadar san uair"
• Greek: "χιλιόμετρα ανά ώρα" (a different script).

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.

Conversions

• ≡ , the SI unit of speed, metre per second
• = 0.2 m/s
• ≈ ≈
• ≡ (exactly)
• ≡

Notes

References

References

1. Develey, Emmanuel. (1802). "Physique d'Emile: ou, Principes de la science de la nature".
2. {{cite OED. k.p.h.
3. [https://www.merriam-webster.com/dictionary/kph "kph."] [[Merriam-Webster. ''Merriam-Webster.com'']]. Retrieved 10 September 2023.
4. [https://www.collinsdictionary.com/dictionary/english/kph "kph."] ''[[Collins English Dictionary]]''. Retrieved 10 September 2023.
5. [https://books.google.com/books?id=hCs6AAAAIAAJ&dq=km/hr&pg=PA126 ''Journal of Research of the National Bureau of Standards: Radio propagation. D'', Volume 65, pp. 122–126. 1961.] [[National Bureau of Standards]]. ''Google Books''. Retrieved 10 September 2023.
6. {{SIbrochure9th
7. "kph abbreviation".
8. "The Oxford English Dictionary".
9. (1971). "The Compact Edition of the Oxford English Dictionary". Oxford University Press.
10. Frazer, John F.. (November 1866). "Journal of the Franklin Institute of the State of Pennsylvania for the Promotion of the Mechanic Arts". Franklin Institute.
11. (May 1889). "American meteorological journal: A monthly review of meteorology, medical climatology and geography". Meteorological Journal Company.
12. (February 1895). "Power consumed on electric railways". The Street Railway Journal.
13. (1898). "Bulletin – United States Geological Survey, Volumes 151–152". USGS.
14. Whipple, F. J. W.. (1899). "The Stability of the Motion of a Bicycle". The Quarterly Journal of Pure and Applied Mathematics.
15. Launhardt, Wilhelm. (1900). "The Theory of the Trace: Being a Discussion of the Principles of Location". Lawrence Asylum Press.
16. Swinburne, J. (July 1902). "The Electric Problem of Railways". The Railway Engineer.
17. Figee, S.. (1903). "Observations Made at the Royal Magnetical and Meteorological Observatory at Batavia". Government of Netherlands East India.
18. Hobart, H. M.. (1910). "Electric Trains". D. Van Nostrand Company.
19. Ball, Jack. (August 1911). "Foreign Notes on Aviation". Town & Country.
20. Dodd, S. T.. (January 1914). "A Review of Some European Electric Locomotive Designs". General Electric Review.
21. (October 1915). "Data on Mixed Motor Fuels of Interest for American Export Trade". The Automobile.
22. (December 1916). "Tractive resistance tests with an electric motor truck". Engineering and Contracting.
23. al-Jawwīyah, Maṣlaḥat al-Arṣād. (1921). "Meteorological Report for the Year [1916?]". Ministry of Public Works, Egypt.
24. (1922). "French Railway Begins Electrification Program". Simmons Boardman.
25. Blakemore, Thos. L.. (1927). "Pressure Airships". Ronald Press.
26. (1933). "Aircraft Year Book". Aerospace Industries Association of America, Manufacturers Aircraft Association, Aeronautical Chamber of Commerce of America.
27. (1939). "Bulletin". Central Electric Railfans' Association.
28. Thompson, Francis R.. (1940). "Electric Transportation".
29. Truss, Lynne. (2003). "Eats Shoots and Leaves". Profile Books.
30. (April 2008). "Reuters Handbook of Journalism". Reuters.
31. "The Economist Style Guide, 12th Edition".
32. (June 2012). "klick". [[Oxford English Dictionary]].
33. Quinn, Terry. (2012). "From Artefacts to Atoms: The BIPM and the Search for Ultimate Measurement Standards". [[Oxford University Press]].
34. {{SIbrochure8th
35. Danloux-Dumesnils. (1969). "The Metric System: A Critical Study of its Principles and Practice". The Athlone Press of the University of London.
36. (1 December 2006). "RLO: SI Units". School of Nursing and Academic Division of Midwifery; University of Nottingham.
37. "Information and Harmonization". [[International Bureau of Weights and Measures]] and [[International Organization of Legal Metrology]].
38. (2000). "OLA Editorial Style Guide". [[Open Learning Agency]] (OLA), Government of British Columbia.
39. (2012). "Conspicuity and Signs: Road signing". [[International Red Cross and Red Crescent Movement#International Federation of Red Cross and Red Crescent Societies (IFRC).
40. (November 2010). "Traffic Signs Manual". Department of Transport.
41. {{cite EU directive. (18 October 1971)
42. {{CELEX. 31980L0181
43. {{cite EU directive. (26 June 1975)
44. National Highway Traffic Safety Administration. (May 2000). "Federal Motor Vehicle Safety Standards; FMVSS 101--Technical Correction--Speedometer Display". Federal Register.
45. National Highway Traffic Safety Administration. "Federal Motor Vehicle Safety Standard (101: Controls and Displays)".