Effects of Prolonged Driving on Time Headway Adopted by HGV (Heavy Goods Vehicle) Drivers

Truck driver safety was studied under conditions of prolonged normal driving, prolonged continuous convoy driving, and continuous convoy driving under conditions of task uncertainty. In all experiments drivers were required to drive an experimental truck for 4 consecutive days. Dependent variables were driver performance, self-ratings, and endocrine changes. Apart from changes over time, when possible the effects of age and time of work period onset were determined. Symptoms of fatigue were most typical of the end of the driving shift, becoming evident from about the 9th hour of driving, and were particularly characteristics of older drivers on a shift finishing at 02.30 hours. Nevertheless, the requirement to drive 11 hours per day for 4 consecutive days did not lead to conspicuous deterioration in driving performance under normal driving conditions. Even prolonged continuous convoy driving did not produce impairment but elicited compensatory adjustments toward the end of the late shift. Finally, task uncertainty was not found to induce earlier fatigue. Drivers appeared to adjust to this condition by covertly anticipating a demand in excess of actual requirement.