The heavy vehicle driver fatigue project is the first international large scale project to validate alertness monitoring technology and use it to evaluate the impact of work-rest scheduling features on alertness and drowsiness in order to inform fatigue policy. Four different data sets were used including: two detailed instrumented vehicle studies conducted within the project involving more than 300 driver shifts; and collection and evaluation of retrospective alertness monitoring data from more than 150,000 shifts between 2015 and 2018 in conjunction with industry partners. This enabled evaluation of the impact of timing and duration of shifts, number and pattern of consecutive shifts, and duration and timing of rest breaks on alertness and drowsiness events, with consistent findings from the different project elements.