SLEEP 2011 Abstract Supplement

A. Basic Science XII. Instrumentation and Methodology
two 5-day simulated shift work periods separated by a rest break of one
or two days. 11 subjects were assigned to a day shift condition (daily
TIB 22:00-08:00), whereas 24 subjects were assigned to a night shift
condition (daily TIB 10:00-20:00). In both day and night shift conditions,
each shift work day included four 30min driving sessions, at fixed
intervals over time of day (AM or PM depending on condition). Subjects
drove a simulated Ford Taurus in a standardized scenario of rural highways
in a high-fidelity driving simulator (PatrolSim IV, MPRI, Salt Lake
City, UT). Ten straight, uneventful road segments with a speed limit of
55mph (cumulative driving time ~5min) were designated to extract 87
potential driving performance metrics (72Hz sampling).
Results: The variance in the data set of 35 subjects by 40 driving sessions
by 87 metrics was examined with principal component analysis.
This yielded two dominant dimensions of driving performance, which
were represented by metrics reflecting steering variability and lane
deviation, respectively. The steering dimension explained 39% of the
variance and the lane dimension explained another 9% of the variance.
Mixed-effects ANOVA revealed significant interactions of condition by
time of day for the steering dimension (F=4.26, P