We review research findings on Intelligent Speed Adaption (ISA) and evaluate a self-contained, onboard speed advisory system that alerts drivers when the prevailing speed limit is exceeded (passive ISA). Recent developments in technology, including improvements to GPS and other navigation aids, mean that ISA has become a commercial reality rather than an experimental novelty. Extensive trials of ISA throughout the world have demonstrated the potential for significant accident savings as well as other community benefits. There is a compelling case for governments to actively support ISA implementation. This paper examines the role of speeding in road accidents, the reasons for speeding, ISA technology, trials and limitations of ISA, potential benefits and implementation issues.