Variable speed limits (VSL) have been trialled in the US and Europe since the 1960s. VSL are used to manage speed with the aim of improving safety and sometimes motorway performance. In Australia, VSL pilot projects have been deployed in Sydney, Melbourne, Adelaide and Brisbane. The applications of VSL include speed management for safety and congestion, speed control for inclement weather, incidents, school zones, shopping strips, tunnels, bridges and roadworks. More VSL projects have been proposed throughout Australia and a consistent evidence-based approach is warranted. This paper briefly reviews the designs and outcomes of some VSL systems that have been implemented or tested on overseas and domestic motorways. Most VSL installations reviewed in the literature were found to have significant safety benefits. Driver compliance with speed limits was generally improved and this resulted in reduced mean speeds and less speed variance. Drivers experienced fewer crashes, shorter journey times and found the road system to be more reliable. There was also a positive impact on the environment.