This Tech Brief summarises the final report of a study by the same title, which was conducted as a part of a major program by the Federal Highway Administration to investigate commercial driver fatigue in commercial motor vehicle (CMV) operations. The study investigated the possibility that longer-combination vehicles (LCVs), with their increased length, greater weight, and greater number of trailers, could significantly increase the amount of stress and fatigue experienced by the driver. The study was limited to the issue of fatigue under proper and normal operating conditions; it was not intended as an investigation of the safety of these vehicles. Three general conclusions regarding configuration effects that can be drawn from the study results are: (1) Configurations and other task demands consistently affected performance, subjective workload, and fatigue/physiological state following a single, C-dolly, A-dolly (SCA) pattern. The A-dolly configuration resulted in the highest level of workload and fatigue, the C-dolly configuration resulted in the next highest level, and the single-trailer configuration resulted in the lowest level of workload and fatigue. (2) Driver differences were prominent in all analyses representing between 32% and 51% of the relative mean squares for lane-keeping and workload variables. The results indicate that some drivers are challenged by the driving task and support adoption of means to reduce this challenge, particularly when driving triples. (3) Configurations also have consistent carryover effects of physiological effects, driver subjective workload, and lane-keeping performance, and imply that triple-trailer drivers generally would be expected to maintain a higher probability of safe operation with the Super C-dolly configuration than with the standard A-dolly configuration. (Author/publisher)
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