In May 1975 the general speed limit on rural roads was raised from 80 km/h to 90 km/h. Speed measurements were taken in Transvaal over a period of two years from November 1973 onward. One of the findings reported is that daytime speeds of light motor vehicles, operating at free flowing conditions after the introduction of the 80 km/h speed limit, increased by approximately 5 km/h when the speed limit was changed to 90 km/h and have remained fairly constant since then.
Abstract