The Johns Drowsiness Scale (JDS™) is a 10-point scale; a score of 0 = ‘very alert’ and 10 = ‘very drowsy’. The JDS™ is used to define the exactly level of drowsiness experienced by operators using Optalert’s early-warning drowsiness detection products. Recent evidence has shown the JDS™ can be applied to other sensor technologies capable of measuring eyelid aperture, even at relatively low sampling rates.
The ability to objectively identify the earliest signs of drowsiness removes uncertainty and subjective bias that can influence a professional operator’s judgment, even though they are expected to remain vigilant in the workplace.
Peer-reviewed research has shown as levels of drowsiness increase, the risk of performance failure also increases. The term ‘performance failure’ refers to the inability of a person to respond appropriately, such as failing to respond to a visual stimulus (for example, responding to a stop signal) or failing to turn the wheel during a bend in the road. A drowsy driving crash will occur if a performance failure coincides with the need to perform a safety critical task.
The risk per minute begins to increase only slightly as JDS™ scores rise above 3.0. This risk increases substantially at JDS™ scores of 4.5 or above. Once JDS™ scores reach 5.0 or more, the risk of performance failure (i.e. the risk of a drowsy crash) is sufficiently high, in fact, several times higher than for an alert driver.
Independent research has shown JDS™ scores at medium risk levels indicate performance impairment equivalent to a blood alcohol concentration of 0.05, the legal limit on roads in many countries. High risk JDS™ scores correspond to impairment equivalent to a BAC level of 0.08. These levels of impairment are similar to being awake for 17 and 21 hours respectively.