3.0 Study Design
The primary goal of the study was to determine whether information feedback from a combination of the more promising fatigue management technologies would (1) enhance truck driver alertness, especially during night driving, and (2) increase sleep time, while driving under current hours-of-service in the United States and Canada. As noted above, since it was neither cost-effective nor practical to conduct a separate study of each individual technology, the selected representative four FMT technologies were combined and tested as a set within in a single field trial that had two phases. Study Phase 1 (data collection in 2002) took place under Canadian hours-of-service, and involved a Canadian trucking company (Challenger Motor Freight, Ontario, Canada) in which volunteer drivers operated single tractor-trailer units with sleeper berths, and approximately 74% of their driving was conducted during daylight hours. Study Phase 2 (data collection in 2003) took place under U.S. hours-of-service, and involved a U.S. trucking company (Con-Way Central Express, Ann Arbor, Michigan) in which volunteer drivers operated tandem tractor-trailer units without sleeper berths, and approximately 93% of their driving was conducted during nighttime hours. The difference between Canadian and U.S. trucking companies were in part a function of which companies agreed to be part of the study, as well as our goal to expressly study companies in which night driving was both a minority (Study Phase 1) and a majority (Study Phase 2) of trucking operations.
To compare the effects of feedback from combined fatigue management technologies with no feedback from FMT technologies, a within-subjects cross-over design was used in both phases (countries) of the study. The design did not require manipulating or controlling what the participating companies and drivers did, what schedules the drivers adhered to, or what operating practices they actually followed. Rather, the FMT intervention and data collection were applied to existing routine trucking operations. Thus, for the comparisons of the effects of FMT FEEDBACK vs. NO FEEDBACK, volunteer drivers served as their own controls-undergoing both conditions under nearly identical circumstances.
Each driver underwent the two conditions in the same order: 2-weeks of the NO FEEDBACK (baseline control condition) occurred first, followed by 2-weeks of the FMT FEEDBACK (intervention condition). Condition order was not counterbalanced because providing the NO FEEDBACK condition after the FEEDBACK condition would have involved a change in driver behavior carried over from the FEEDBACK condition (i.e., drivers might have opted to turn on the feedback information from devices while in the NO FEEDBACK condition). In contrast, by providing the NO FEEDBACK condition first, drivers engaged in their normal driving practices for 2 weeks, although their driving performance, drowsiness and sleep need were still recorded by the relevant FMT technologies (i.e., FMT devices were recording but not providing feedback). The NO FEEDBACK condition therefore served as a baseline against which the FMT FEEDBACK intervention was compared. Again, each driver participant was scheduled to undergo each condition (NO FEEDBACK and FEEDBACK) for a period of 14 days per condition (i.e., approximately 28 days total for study participation).
There were a number of considerations that went into selecting a design to address the specific aim and hypothesis. A cross-over (or treatment-by-treatment) design uses subjects as their own controls. It is efficient, and it has a number of advantages over an independent-groups design. It ensures roughly the same inter-subject variability across both conditions (by and large the results of the study confirm this was the case). It provides an opportunity for subjects to explicitly compare and contrast conditions. It requires fewer subjects than an independent-groups design, which makes it more feasible from both cost and timeline perspectives. On the downside, a cross-over design necessarily burdens a smaller group of subjects with more recording time than would be the case in an independent-groups design. If too burdensome, subjects may fail to complete all conditions. This occurred to some extent in both phases of the present study, but was not a major problem.