Direct Mapping to the KSS

Within the European Union’s (GSR (EU) 2021/1341) definition, a Driver Drowsiness and Attention Warning (DDAW) system may provide a warning to the driver at a KSS (Karolinska Sleepiness Scale) level of 7 and must provide a warning at a KSS level of 8 or above. The regulation allows the use of alternative measurements to the subjective KSS to determine the participant’s level of drowsiness, provided there is evidence that it is valid and accurate.

Optalert’s scientifically validated Johns Drowsiness Scale (JDS) is a composite scale (0 = Very alert, 10 = Very drowsy) based on different features reflecting the short-term variability of blinks and eyelid closure characteristics. Measured each minute, JDS provides a single, sensitive measure of driver impairment due to drowsiness. The system has been developed based on 20 years of research into the physiological effects of drowsiness and implemented commercially in professional driver fleets for over 10 years.

There is a direct, linear relationship between the KSS and JDS, so we can validate your DDAW solution against the requirements of GSR (EU) 2021/1341, simply, quickly and remotely – today.

The graph demonstrates the relationship (with a 95% confidence interval) between the KSS and Optalert’s JDS. To achieve compliance, your DDAW can generate an optional early warning at KSS of 7 and a compulsory alert at KSS of 8 – when the driver requires some effort to stay awake. These directly map to JDS values of 4.3 and 5.9.

  1. Optalert provides validated mapping between KSS and JDS.
  2. Optalert provides evidence detailing the equivalency between a given JDS and a KSS level of 7 and 8.
  3. Optalert can incorpate its JDS based system into any DDAW system with eyelid movement.