according to statistics for 2003, 9 in 100,000 people in canada died from driving accidents. a high percentage (30-40%) of these took place due to sleepiness on monotonous road conditions. therefore, driver vigilance must be studied in order to attempt to decrease these fatal accidents. thiffault and bergeron (2003) have proposed a model for fatigue and vigilance which involves both endogenous and exogenous factors. in this framework, endogenous factors would include any fluctuation in alertness which originates from within the driver, such as circadian variations associated with the time of day, fatigue generated from the task itself, and sleep related problems that the individual may be suffering. exogenous factors that influence driving vigilance are those which come from the task itself, such as road geometry and road-side environmental cues. the authors also suggest that mental under-load caused by such driving conditions could be as important as overload from urban expressway conditions.