Novice drivers’ performance after different alcohol dosages and placebo in the divided-attention steering simulator (DASS)

RationaleThe divided-attention steering simulator (DASS) is designed to measure lane-keeping (i.e., a tracking task using a steering wheel) while performing a secondary visual task (responding to digits that appear in the corners of the computer screen). Some studies have already used the DASS, but the magnitude of impairment is difficult to interpret because reference values are lacking.ObjectiveTo examine the magnitude of impairment after administration of four different dosages of alcohol and placebo.Materials and methodsThirty-two healthy young adults participated in this randomized, single-blind crossover trial. Subjects received alcohol to gain a blood alcohol concentration (BAC) of 0.02%, 0.05%, 0.08%, and 0.10% or alcohol–placebo. Sixteen subjects performed a 30-min test in DASS (dual-task condition). Outcome measures were steering error, reaction time, and percentage of errors. Sixteen other subjects performed the test without performing the secondary peripheral task (single-task condition).ResultsTwenty-eight subjects (novice drivers; drivers’ license up to 5 years) were included in the analyses. Dose-dependent impairment was found in both the single-task condition (F(4,11) = 10.86, p < 0.001) and the dual-task condition (F(4,9) = 5.58, p < 0.015). Performance at all BAC levels differed significantly (p < 0.05) from alcohol–placebo, except BAC 0.02%. With increasing BAC levels, subjects made more errors and reacted slower on the peripheral visual search task, but these effects did not reach significance.ConclusionWith increasing BAC, dose-dependent impairment was found. The DASS seems to be a suitable divided-attention task that is useful in psychopharmacological research and training of novice drivers.