Martin Vlietstra was living in South Africa when the Republic changed from imperial to metric
"South Africa was a success story as regards metrication. The metrication process started in 1967 with the appointment of a Metrication Advisory Board to plan and co-ordinate the changeover to the metric system in South Africa.
At the time, the South African Government was intensifying its Apartheid legislation and was rapidly becoming a pariah in the world. To their credit, however, they were the first of the Commonwealth countries to have replaced an existing £.s.d. system with a decimal currency. This conversion had gone fairly smoothly and great pains were taken to ensure that the largely illiterate black population were not disadvantaged as a result of decimalisation.
From the point of view of the public, the bulk of the metrication process was carried out over a two year period between 1971 and 1973. Dual units were not used on packaged goods - initially, packaged goods remained the same size but with the Imperial quantity replaced by a metric quantity. For example, 2 lb tins of jam were replaced by 907 g tins. Road signs were replaced over a period of a few months with an entirely new style of road sign. The new style was close to the "European" style, but with the white fields replaced by a blue field. As with other measurements, speedometers with dual units were unknown - cars that were built up to about 1971 had mph speedometers and those from about 1972 had km/h speedometers.
One of the biggest differences between the metrication processes in the United Kingdom and in South Africa was the degree of compulsion in South Africa. The South African Government, having a history of authoritarianism, took some simple steps to speed up metrication - the sale of measuring devices that were calibrated in imperial units whether on their own or in conjunction with metric units was prohibited and the media was forbidden to use imperial units. For a number years recipes in newspapers and women's magazines would have recipes that needed 454 g of flour. A few years later this became 450 g and then finally 500 g. Similarly, I have a kitchen measuring jug that is in French and English rather than English and Afrikaans or English only - such devices were not manufactured in South Africa and nobody manufactured them using only English and metric units.
Of course the degree of compulsion brought some resistance though the biggest resistance that I recall came from the local authority where my parents lived. Certain officials refused to accept building plans in metric units for some time when the law required that metric units be used. Politically, the authority concerned (Carletonville) was run by the National Party, the same party as the Government. The English-language press (who were often vocal in their opposition to Apartheid) did not oppose metrication - nor on the whole did the population as a whole: they saw metrication as progress and put up with the inconveniences as part of the process that was to bring South Africa into line with the rest of the world. Most of South Africa's large trading partners such as France, Germany and Japan were already using metric units and others such as the United Kingdom and Rhodesia (now Zimbabwe) were in the process of converting to metric units. At that time, as now, South Africa had comparatively little trade with the United States.
The Metrication Advisory Board was disbanded in 1977 with its job complete. After it was disbanded the restrictions that were imposed were no longer enforced and people were free to use whatever units of measure they preferred. Apart from the use of feet and inches for people's heights, South Africa today is a metric country.
My own view is that the South African changeover, while being a little rough on the edges, recognised that people will only change over to metric usage once the imperial crutch has been withdrawn. In contrast, successive British Governments did not have the will to remove the crutch with the resultant mess that in which we find ourselves today."
[Notes: South African decimalisation took place on 14 February 1961. South Africa withdrew from the Commonwealth on 31 May 1961 and was re-admitted in 1994.]