This paper describes some initial investigations of the feasibility of development of a driver fatigue warning system for trucks. Extensive measurement of drowsiness and vehicle control variables was undertaken on trucks and drivers in normal operation. The result suggests that the phenomenon of less frequent but larger steering wheel movements which underlies the Renault system for detection of drowsiness in car drivers is also present in trucks. The steering wheel angles observed are larger, however, and this may require revision of the algorithms to more effectively detect fatigue in truck drivers.