The Department for Transport has identified the need for a critical evaluation of up-to-date evidence to accurately determine the current scale of the driver fatigue problem in the UK, and to highlight evidence gaps that may require further research. A consortium consisting of Clockwork Research, the University of Leeds and the Transport Research Laboratory (TRL) have worked together to produce a report that meets the objectives of the Department for Transport; namely, to provide a comprehensive and critical review of the literature that synthesises the evidence relating to fatigue and road safety. The Department for Transport research specification identified a list of research questions that were to be addressed by this project. These questions were distributed between the three teams collaborating on the project. Following an inception meeting, each team worked independently to identify and critically evaluate the key sources relevant to their research questions, according to criteria agreed with the client at the inception meeting. This report is structured around the research questions identified as being of interest by the Department for Transport. Each section begins with a summary of the evidence identified as being of most relevance and importance, and then sets out any evidence gaps that the review identified.