RESEARCH over several decades has implicated shiftwork as a major cause of work-·related fatigue and decreased health and safety. However, discriminating between different rosters in terms of fatigue has been difficult. This is partially due to the large number of different rosters currently worked as well as the significant costs associated with laboratory-based roster assessments. Due to difficulties with traditional laboratory-based methods of modelling rosters, it is the authors' aim to develop a quantitative approach based only on the timing and duration of work periods. The potential applications of quantitative fatigue modelling in monitoring health and safety outcomes are also discussed. Specific examples are given for quantifying fatigue in road transport. In conclusion, this model provides a simple, straightforward approach to quantifying fatigue. It also enables organisations to model the relationship between hours of work and health and safety outcomes or to model the implications of proposed roster changes.