Driver sleepiness accounts for a substantial proportion of fatal and severe crashes

1. Driver Sleepiness Self-regulationPhysiological & Subjective Evidence NRMA - ACT ROAD SAFETY TRUST Christopher N Watling & Simon S Smith Centre for Accident Research and Road Safety - Queensland, Institute of Health and Biomedical Innovation, Queensland University of Technology, Brisbane, Queensland, Australia 30min nap break KSS2 Hazard Perception driving simulation task I N T R O D U C T I O N I N T R O D U C T I O N • 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 M E T H O D M E T H O D EEG KSS1 • 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: 15-76 mins) • Subjective sleepiness: Significant increase from the beginning of driving (KSS1M = 6.6±0.7) to the cessation of driving (KSS2M = 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: 1.5-24 mins) R E S U L T S R E S U L T S 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 Data for 23 participants; SOL = sleep onset latency (mins); REM = Rapid eye movement • 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 • D • I • S • C • U • S • S • I • O • N • D • I • S • C • U • S • S • I • O • N christopher.watling@qut.edu.au