This report compares the speeds of cars and articulated trucks before and after the change in heavy vehicle speed limit to 100 km/h on 1 July 1988. Comparable data before and after this time were collected at 62 sites in New South Wales, Victoria, Queensland, South Australia, Western Australia and Tasmania. Faster articulated truck and car speeds were recorded at most (four fifths) of the sites after the speed limit change compared with before the change. The mean speeds of cars and articulated trucks were closer after the change compared with before for most sites. The percentages of sites for which truck speeds increased, for which car speeds increased, and for which car and truck speeds became closer rather than further apart, are each statistically significant. These three results remain true when the analysis is restricted to sites with appreciable data.