Driver sleepiness accounts for a substantial proportion of fatal and severe crashes A critical component to mitigate sleep-related crashes is the driver’s awareness of their sleepiness Drivers that are aware of increasing sleepiness levels can self-regulate their driving by taking appropriate actions - such as ceasing to drive and then having a nap break Effective self-regulation requires accurate self-awareness of sleepiness when driving However, the accuracy of self-awareness may vary between individuals The aim of this study was to assess drivers’ capacity to identify their own sleepiness, and self- regulate driving cessation, during a validated driving simulator task Participants: 26 young adult drivers (20-28 yrs) who were partially sleep deprived (05:00 wake up) completed a hazard perception driving simulation task in a laboratory Measures: Sleepiness was assessed via physiological (EEG) and subjective measures (Karolinska Sleepiness Scale: range of 1 “ extremely alert ” to 9 “ very sleepy, great effort to keep awake, fighting sleep ”) Participants were instructed to “Stop when you think you would be too sleepy to drive safely on the road” After driving cessation participants were then offered a nap opportunity No participant fell asleep during the driving task via standard criteria The mean duration of driving before cessation was 36.1 mins (±17.7 mins; range: mins) Subjective sleepiness: Significant increase from the beginning of driving (KSS1 M = 6.6±0.7) to the cessation of driving (KSS2 M = 8.2±0.5), t(25) = -11.8, p <.001 Physiological sleepiness: No change in EEG spectral power for theta (t(25) = 1.9, ns) and alpha frequency bands (t(25) = -1.3, ns) 23 of the 26 participants achieved sleep onset during the nap opportunity (SOL range: mins) Sleep time (% of total) SOLDurationStage 1Stage 2Stage 3Stage 4REM 8.61± ± High levels of sleepiness (KSS level 6 “ some signs of sleepiness ” and level 8 “ sleepy, some effort to stay awake ”) were reported during the daytime driving task after very moderate sleep restriction On-road driving at these levels of subjective sleepiness (KSS 6 and 8) correspond to a 5 and 15 times increase in the likelihood of having a fatal or severe crash All participants were able to perceive increasing sleepiness during the driving task despite no observed change in standard physiological indices of sleepiness The participant’s subjective sleepiness levels had behavioural validity with a high ‘napability’ at the point of driving cessation The influence of driving demands (destination arrival, time constraints) on driver sleepiness self- regulation will need to be assessed by future research This study found these drivers could perceive increasing sleepiness and decide to cease driving Data for 23 participants; SOL = sleep onset latency (mins); REM = Rapid eye movement NRMA - ACT ROAD SAFETY TRUST DISCUSSIONDISCUSSION RESULTSRESULTS METHODMETHOD INTRODUCTIONINTRODUCTION 30min nap break KSS2 Hazard Perception driving simulation task KSS1 EEG