Metrication in Australia
Metrication in Australia took place between 1970 and 1988. Before then, 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 Between 1970 and 1988, imperial units were withdrawn from general legal use and replaced with SI metric units, facilitated through legislation and government agencies.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, 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 electronics and chemical industries worked in metric units. 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." 
In 1970, the Parliament of Australia passed the Metric Conversion Act, which 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.
- 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 weights 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 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.
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.
"As a result of all these changes, conversion on the roads occurred without incident."
Metrication is mostly complete. Road signs are totally metric, as are the speedometers and odometers in motor vehicles and the sale of oil and petrol is by the litre. Vehicle tyre pressures are still commonly talked about in pounds per square inch.
Fruit 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 30 cm, thereby approximating foot lengths, while pipes and conduits may have internal diameters of 19, 25 and 32 mm (based on 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:
- Weight is referred to in kilograms, and baby nappy sizes are specified in kilograms only but some parents give their baby's birth weight in pounds and ounces, however this has become less common.
- Heights for official and sporting purposes are given in centimetres. In informal and private contexts a person's height is 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 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.
Imperial measurements are used in preference to metric usually where the product originates or is intended for an American market (printers, hard-disk drives) or when the size increment for a product is a multiple of an inch (televisions and tyres). A few examples are:
- Scuba diving uses metric measures but the altitude for sky diving is routinely given in feet.
- Aviation, as in many other metric countries, uses 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 metric, in hectopascals and degrees Celsius respectively). Height or altitude is always in feet and vertical speed (rate of climb or descent) is in feet per minute.
- Australia uses metric paper sizes for printing but the term dots per inch (dpi) is still used in printing pictures. 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 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 are often given in both kilopascals and pounds per square inch.
- TV screens and LCD monitors may use inches 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.
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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