Metrication in Australia
Metrication in Australia effectively began in 1966 with the conversion to decimal currency under the auspices of the Decimal Currency Board. The conversion of measurements—metrication—commenced subsequently in 1971, under the direction of the Metric Conversion Board and actively proceeded until the Board was disbanded in 1981.
Before 1970, Australia mostly used the imperial system for measurement, which the Australian colonies had inherited from the United Kingdom. Between 1970 and 1988, imperial units were withdrawn from general legal use and replaced with SI metric units, facilitated through legislation and government agencies. SI units are now the sole legal units of measurement in Australia. Australia's largely successful transition to the metric system contrasts with the ongoing opposition to metrication in the United States, Canada and the United Kingdom.
Although there was debate in Australia's first Parliament after federation to consider adopting the metric system, metric units first became legal for use in Australia in 1947 when Australia signed the Metre Convention (or Convention du Mètre). However, Imperial "Weights and Measures" were most commonly used until the Commonwealth government began the metric changeover in the 1970s. In 1960, SI units were adopted as a worldwide system of measurement by international agreement at the General Conference on Weights and Measures. The metre, kilogram, second, ampere, kelvin,[nb 1] candela and mole were defined as base units in this system and units formed from combinations of these base units were known as "derived units". SI units were subsequently adopted as the basis for Australia's measurement standards, whereby they were defined as Australia's legal units of measurement.
In 1968, a Select Committee of the Australian Senate examined metric "Weights and Measures" and came to the unanimous conclusion that it was both practical and desirable for Australia to change to the metric system. Some of their considerations included the "inherent advantages of the metric system" that meant that weighing and measuring was facilitated, "often with substantial increases in efficiency". Educationally, the reform would "simplify and unify the teaching of mathematics and science, reduce errors, save teaching time and give a better understanding of basic physical principles". In 1968, more than 75% of Australia's exports went to metric countries, and at that time it was noted that all countries except the United States were metric or were converting to the metric system. It was also noted that because of Australia's large migrant programme, more than 10 per cent of people over 16 years of age had used the metric system before coming to Australia. They also noted that school pupils were widely familiar with the metric system because it had been taught in the schools for many years.
By 1968, metrication was already well under way in Australian industry. The pharmaceutical industry had metricated in 1965 and much of the chemical and electronics industries worked in metric units—there being no "Imperial" units for the latter. One of the country's major automobile manufacturers had already declared its intention to metricate before the Government announced its decision to change to the metric system. "The change itself provided a unique opportunity to rationalise and modernise industrial practices and bring Australia's technical standard specifications into accord with those adopted internationally".
On 12 June 1970, the Australian Metric Conversion Act passed by the Australian Parliament was given assent. This Act created the Metric Conversion Board to facilitate the conversion of measurements from imperial to metric. A timeline of major developments in this conversion process is as follows:
- 1971 – the Australian wool industry converted to the metric system.
- 1972 – all primary schools were teaching the metric system alone. Many had been teaching both imperial and metric and later, metric alone since Australia changed to the decimal currency system in 1966. Horse racing converted in August 1972 and air temperatures were converted in September 1972.
- 1973 – all secondary schools were now using the metric system.
- 1974 – large scale conversion across industries, including packaged grains, dairy products, eggs, building, timber, paper, printing, meteorological services, postal services, communications, road transport, travel, textiles, gas, electricity, surveying, sport, water supply, mining, metallurgy, chemicals, petroleum and automotive services. Most beverages, aside from spirits, also converted to metric units by the end of 1974. The conversion of road signs took place in July 1974. There was a publicity campaign to prepare the public.
- 1976 – the Building and Construction industry completed its change to metric measurements (within two years) by January 1976.
- 1977 – all packaged goods were labelled in metric units, and the air transport, food, energy, machine tool, electronic, electrical engineering and appliance manufacturing industries converted.
- 1987 – The Real estate industry converted to metric.
- 1988 – Metrication completed, with the metric system becoming the only system of legal measurements in Australia.
The Metric Conversion Board spent A$5.955 million during its 11 years of operation, and the federal government distributed $10 million to the states to support their conversion process. The cost of metrication for the private sector was not determined but the Prices Justification Tribunal reported that metrication was not used to justify price increases.
Opposition to metrication was not widespread. The Metric Conversion Board did not proceed with education programmes as polling revealed that most people were learning units and their application independently of each other, rendering efforts to teach the systematic nature of the metric system unnecessary and possibly increasing the amount of opposition.
The Metric Conversion Board was dissolved in 1981, but the conversion to the metric system was not completed until 1988. Between 1984 and 1988, the conversion was the responsibility of the National Standards Commission, later renamed the National Measurement Institute. In 1987, real estate became the last major industry to convert, and, in 1988, the few remaining imperial units were removed from general use.
Restrictions of volume and masses that had previously compelled manufacturers to package products to rounded imperial sizes despite metric labelling, for example packaging a soft drink can as a rounded 13 imp fl oz but labelling it as 375 ml, were removed in 2008.
Metrication of horse racing
An early change was the metrication of horse racing. This was facilitated because the furlong (one eighth of a mile) is close to 200 m. Therefore, the Melbourne Cup was changed from 2 miles (about 3,218 m) to 3,200 m. The first metric Melbourne Cup was raced in November 1972.
Metrication of weather reporting and forecasts
When the Australian Bureau of Meteorology was enlisted to introduce the metric system for weather reporting and forecasts, its public relations officer, Godfrey Wiseman, coined a series of jingles to educate the public, using the terms "frosty fives", "tingling tens", "temperate twenties", "thirsty thirties" and "fiery forties" to describe human sensation to temperatures in degrees Celsius. This was very successful because the public soon became aware of the significance of the descriptions.
As the culmination of this campaign, weather reports and forecasts in both Imperial and metric measures were only provided for one month. After that, purely metric measurements were used for temperature, wind speed, rainfall, air pressure and other meteorological phenomena.
Metrication of the road signs
An important and very visible sign of metric conversion in Australia was the change in road signs and the accompanying traffic regulations; "M-day" for this change was 1 July 1974. Because of careful planning, almost every road sign in Australia was converted within a month. This was achieved by installing covered metric signs alongside the imperial signs before the change and then removing the imperial sign and uncovering the metric sign during the month of conversion.
While road signs could not all be changed at the same time, there was little chance of confusion as to what any speed limit sign meant during this short change-over period. This was because the previous (MPH) signs had the signage in black on white and were rectangular, in the same style as current US speed limit signs, while the (km/h) signs which replaced them had the number indicating the speed limit inside a red circle, as is done in Europe.
Road distance signs were also converted during this period. To avoid confusion as to whether the distance indicated was in miles or kilometres all the new kilometre signs had affixed to them a temporary yellow plate, on which was indicated the corresponding number of miles. These temporary plates were removed after about one year.
Except for bridge-clearance and flood-depth signs, dual marking was avoided. Though people opposed to metrication expressed the fear that ignorance of the meaning of metric speeds would lead to slaughter on the roads, this did not happen as most drivers under the age of 25 had been taught metric units at school and through them, their parents were familiar with metric speeds if not metric units as a whole.
It was believed that public education would be the most effective way of ensuring public safety. A Panel for Publicity on Road Travel, made up of the various motoring organisations, regulatory authorities and the media, planned a campaign to publicise the change. The resulting publicity campaign cost $200,000 and the Australian Government Department of Transport paid for it. The Board also produced 2.5 million copies of a pamphlet, "Motoring Goes Metric". This was distributed through post offices, police stations and motor registry offices.
"For about a year before the change, motor car manufacturers fitted dual speedometers to their vehicles and, after 1974, all new cars were fitted with metric-only speedometers. Several kinds of speedometer conversion kits were available.
Building and construction
The building industry was the first major industry grouping in Australia to complete its change to metric. This was achieved within two years by January 1976 for all new buildings other than those for which design had commenced well before metrication began. The resulting savings for builders and their sub-contractors has been estimated at about 10% a year of gross turnover.
In this the industry was grateful to the SAA (now Standards Australia) for the early production of the Standard AS 1155-1974 "Metric Units for Use in the Construction Industry", which specified the use of millimetres as the small unit for the metrication upgrade. In the adoption of the millimetre as the "small" unit of length for metrication (instead of the centimetre) the Metric Conversion Board leaned heavily on experience in the UK and within the ISO, where this decision had already been taken.
This was formally stated as follows: "The metric units for linear measurement in building and construction will be the metre (m) and the millimetre (mm), with the kilometre (km) being used where required. This will apply to all sectors of the industry, and the centimetre (cm) shall not be used. … the centimetre should not be used in any calculation and it should never be written down".
The logic of using the millimetre in this context was that the metric system had been so designed that there would exist a multiple or submultiple for every use. Decimal fractions would not have to be used. Since the tolerances on building components and building practice would rarely be less than one millimetre, the millimetre became the sub-unit most appropriate to this industry.
Although for the most part they are ignored in everyday life, it was not possible for education in the logical construction of the metric system to ignore the metric prefixes deci, centi, hecto and deka, since the derivation of the litre is dependent upon the knowledge that it derives from the volume of a cubic decimetre, i.e. 1000 cubic centimetres.
However, in Australia, the prefix "centi" has been limited to use with the metre (mainly by the general public not associated with the building industry)—unlike in Europe, where the centilitre may often be encountered.
Metrication is mostly complete. Road signs solely use metric measurements, as do the speedometers and odometers in new motor vehicles; there was no requirement for older vehicles to have their speedometers and odometers converted to metric, so many older vehicles will show miles. Privately imported vehicles, such as classic cars, also do not need to be so converted. The sale of oil and petrol is by the litre. However, vehicle tyre pressures are still commonly talked about in pounds per square inch.
Fruits and vegetables are advertised, sold and weighed by the kilogram, groceries are packed and labelled in metric measures. Schooling is wholly metric. Newspaper reports are mostly in metric terms. In some cases old imperial standards were replaced with rounded metric values, as with horse racing or the size of beer glasses (rounded to the nearest 5 mL). The pre-metric names of beer glass sizes, including the pint, have been retained (although in South Australia the "pint" of beer is not an imperial pint, as it is elsewhere in Australia). Dressed timber is often sold in lengths such as 1.8, 2.1, 2.4, 3.0 and 3.6 metres, each multiples of 300 mm, thereby approximating foot length increments, while pipes and conduits may be specified as having diameters of 12, 19, 25 and 32 etc. mm (based on "soft" conversions" of 1⁄2, 3⁄4, 1 and 1 1⁄4 in).
In some cases goods manufactured to pre-metric standards are available, such as some bolts, nuts, screws and pipe threads and there are some instances where pre-metric measures may still be used:
- Mass is referred to in kilograms, and baby nappy sizes are specified in kilograms only. While some parents may still convert their baby's hospital-stated birth mass to pounds and ounces, the practice of using pre-metric units has become far less common.
- Height is measured and given in centimetres. In informal contexts a person's height is still sometimes stated in feet and inches.
- Domestic and commercial real estate is advertised in square metres or hectares but though crop yields are described in tonnes per hectare, rural land areas are sometimes still advertised in acres.
- Weather reports are always in metric terms but some specialised surf reports give wave heights in feet and there are occasional references to "the old century", meaning 100 °F, when describing temperatures of 38 °C or more.
While Imperial units of measurements may sometimes be specified instead of SI units (usually, where the product originates from or is intended for an American market) apart from area measurements, the use of any measurement except in SI units is not "legal for trade" under current Australian legislation. 
Examples where non-SI units are (sometimes) specified are:
- Aviation, as in many other metric countries, specifies horizontal distances in nautical miles and horizontal speed in knots, but horizontal distance for visibility or clearance from clouds is in kilometres or metres, as are runway dimensions. (The pressure and temperature are also given in SI units, in hectopascals and degrees Celsius respectively). Height or altitude is always specified in feet, as this is vital for safety—as long as one remaining country in the world does not change to metric measurements. (The error in approximating 1000 feet as 300 metres is 4.8 m/16.75 feet. This may be somewhat insignificant at low altitudes. However, the cumulative effect of this error by 30,000 feet (9.15 km) becomes quite significant (144 m/472 feet) The measurement and vertical speed (rate of climb or descent) is given in feet per minute—for much the same reasons height is given in feet.
- The altitude for sky diving is routinely given in feet, which follows from the above existing Aviation "conventions".  (However, Scuba diving uses metric measures)
- Australia uses metric paper sizes for office use and home printing. (A4 = 210 × 297 mm) However, the term dots per inch (dpi) is still used when printing images. The photo printing industry usually uses imperial sizes for photo dimensions (e.g. 4 × 6 inch rather than 10 × 15 cm).
- Historical writing and presentations may include pre-metric units to reflect the context of the era represented.
- Vehicle tyres (as in the rest of the world) mark the rim diameter in inches and the width in millimetres. A car tyre marked '165/70R13' has a width of 165 mm, an aspect ratio (profile) of 70% and a 13-inch rim diameter. Tyre pressures may be given in both kilopascals and "pounds per square inch".
- TV screens and LCD monitors may be described in inches instead of or as well as centimetres, e.g., a Plasma screen may be advertised as 42 inches (106 centimetres), and a computer monitor screen may be advertised in inches.
- Advertising billboards are measured by feet—because of the still pervading influence of USA practices on such activities.
- The illicit drug trade in Australia still often uses imperial measurements, particularly when dealing with smaller amounts closer to end user levels e.g. "8-ball" an 8th of an ounce or 3.5 g; cannabis is often traded in ounces ("oz") and pounds ("p")
The cultural transmission of British and American English in Australia has also been noted to be a cause for residual use of Imperial units of measure.
- The kelvin was known as the degree Kelvin at the time.
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