Method Participants –In total, 26 participants (19 females and 7 males) –Mean age of 24 yrs (SD = 2.46; range = 20-28) Materials –Karolinska sleepiness scale (KSS), 9-point Likert scale –Physiological sleepiness via EEG Driving task: spectral analysis of O1-A2 Nap break: C3-A2 scored for SOL and sleep staging –Driving stimulus: Hazard Perception task Hazard perception is the driving skill to anticipate that a traffic situation may result in a crash or a near miss Importantly it is the only driving skill that has a consistent relationship with actual on-road crashes (i.e., criterion validity) NRMA - ACT ROAD SAFETY TRUST

Method (2) Procedure –On testing days participants woke at 05:00 –No caffeine or alcohol until completion of testing –Instructed to “Stop when you think you would be too sleepy to drive safely on the road” Design –Experimental design: participants randomly assigned to the morning (09:00) or afternoon (14:00) start time NRMA - ACT ROAD SAFETY TRUST 30 min nap break KSS 1KSS 2 Hazard Perception driving simulation task 5 mins EEG Duration of driving

Results  30 min nap break KSS 1KSS 2 Hazard Perception driving simulation task 5 mins EEG Duration of driving Duration of driving: M = 36.1 mins (SD = 17.7; range = 15-76) No participant could have been judged to have fallen asleep by standard criteria NRMA - ACT ROAD SAFETY TRUST M = 6.65 M = 8.15 Sig increase No sig change Theta and alpha power levels

Results (2) Subjective sleepiness (KSS) detected an increase in sleepiness levels Physiological sleepiness (EEG) levels did not change over the duration of drive No circadian effects evident in any data source Large variability of driving durations Thirty minute nap break data (n = 23) Note. SOL = sleep onset latency (min); REM = Rapid Eye Movement Sleep time (% of total) SOL (SD)Duration (SD)Stage 1Stage 2Stage 3Stage 4REM 8.61 (7.78)15.09 (8.11) NRMA - ACT ROAD SAFETY TRUST

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