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The nature and extent of impacts of ITS projects is fundamentally different from those of conventional road projects. Evaluation of ITS projects is complicated by the presence of the unique variables affecting the outcomes of projects, which include driver behavioural response and market penetration issues. ITS project evaluation methods must be developed to the same standard as evaluation procedures for conventional transport investment. It is important that the costs and benefits of both ITS and conventional projects are evaluated comprehensively in order to ensure efficient and cost-effective project selection and prioritisation. There is little historical data available to quantify most ITS impacts and some ITS impacts, such as increased comfort or travel time reliability, are qualitative or difficult to measure or value. There is presently little understanding of the causal relationships between ITS projects and their impacts and often it may not be appropriate to transfer results in space and time. This paper provides a state-of-practice summary of ITS evaluation methods and impact measurement efforts, by drawing on a comprehensive survey of available literature. The results of a survey of practitioners and stakeholders designed to address the main issues are also reported on.