Fatigue management strategies on road and in the workplace involve advice on the need to take breaks when tired. This approach assumes people can assess fatigue effects on performance but this assumption is questionable. The aim of this study was to investigate whether we have access to information about current fatigue state and levels of drowsiness, and the implications for detecting changes in driving performance and the likelihood of crashes in a driving simulator with tired drivers. The results reveal that drivers can report increasing fatigue especially across the earlier part of the drive. Importantly, drivers can detect the likelihood of falling asleep prior to crashing indicating that they can make an informed decision to drive or not drive when tired. This has implications for safety advice to drivers.