Driver fatigue: The importance of identifying causal factors of fatigue when considering detection and countermeasure technologies

Driver fatigue is an ill-defined term in the literature. It has been broadly used to refer to a wide range of driver states, each with different causal mechanisms. Technologies currently exist which enable detection of driver fatigue and interventions that have the potential to dramatically reduce crash probability. The successful implementation of these technologies depends on the cause and type of fatigue experienced. Sleep-related (SR) forms of driver fatigue result from accumulated sleep debt, prolonged wakefulness or troughs in the circadian rhythms. SR fatigue is resistant to most intervention strategies. Conversely, technologies for detecting and countering task-related (TR) fatigue (caused by mental overload or underload) are proving to be effective tools for improving transportation safety. Methods of detecting and counteracting the various forms of driver fatigue are discussed. Emphasis is placed on examining the effectiveness of existing and emerging technologies for combating TR forms of driver fatigue.