K. Stephan, S. Hosking, M. Regan, A. Verdoom, K. Young, N. Haworth. The Relationship between Driving Performance and the Johns Drowsiness Scale as Measured by the Optalert System. Monash University Accident Research Centre: Independent Report.
Executive Summary
...The aim of the current study was to determine whether there is a breakdown is driving performance during the period after which the JDS reaches the cautionary level (4.5) and the critical level (5.0), that is, after the driver is classified as drowsy by the Optalert system. In order to achieve this, the Optalert system warnings were not active within this experiment, that is, the system was only used to measure drowsiness, not to warn the driver of their drowsiness. Based upon previous research using the Optalert system, Sleep Diagnostics defined the period of interest to be 30 minutes after the JDS reached the cautionary or critical levels. The analyses were also repeated for shorter periods, of 15 minutes and 5 minutes after the participant reached the cautionary or critical JDS level. It is important to note that the Optalert system is designed to predict drowsiness well ahead of when a warning would be given, and so, the longer time intervals of 15 minutes and 30 minutes are of greater interest in this study...
