Euro NCAP’s Fatigue and Unresponsive Driver Evaluation

There are four boxes representing general assessment areas that Euro NCAP uses to evaluate safety ratings. The fourth box, known as Safety Assist is subcategorised into four areas, one of which is Occupant Status Monitoring. This category is further subdivided into two areas, one of which is called Driver State Monitoring. Driver State Monitoring is finally subdivided into three assessment areas; two of which are the topic of discussion; Fatigue and Unresponsive Driver.

Euro NCAP also requires the submission of a dossier when Driver Monitoring Systems are submitted for evaluations. The dossier would contain technical assessments that includes evidence that the system can detect these specific conditions in a wide range of driver and environmental characteristics. These include but are not limited to age, sex, stature, skin complexion, eyelid aperture, lighting, eyewear, facial hair and driver behaviour (full list can be found in Euro NCAP’s Safety Assist Assessment Protocol Section 3.5). A description and implementation evidence of warning and intervention following the detection of these conditions will also need to be provided in the dossier (more on this below).


Fatigue refers to a state of weariness resulting from exertion that is prolonged and/or intense. The state of fatigue is often confused with drowsiness, but they are quite different. Under Euro NCAP’s definition, there are three stages of fatigue that are assessed: Drowsiness, Microsleep and Sleep. Euro NCAP allows for up to 30 minutes for the system to form a baseline for driver behaviour. Once the system detects these events, it must provide a warning as well as an intervention in order to achieve maximum points.


Drowsiness is the transitional state between wakefulness and sleep which happens within a few minutes. Euro NCAP uses the Karolinska Sleepiness Scale (KSS), a 9-point scale to assess a person’s drowsiness levels (as shown below). Euro NCAP’s definition of a drowsy driver is when they reach a KSS level of 8 or higher. In the dossier, OEMs must describe their system’s requirements as well as evidence of its ability to detect drowsy drivers.


Microsleep refers to very short periods of sleep (lasting several seconds) when a driver loses consciousness without being aware of it. During this time, the driver’s brain does not properly process information and loses conscious control of what they are doing. Euro NCAP’s assessment criteria for microsleep is generic and open to interpretation and has asked for OEMs to submit their definitions of microsleep and demonstrate evidence of their system’s ability to detect them. Euro NCAP has provided an example of a microsleep event in their assessment protocol; a short duration (between 1 and 2 seconds) eyelid closure after a build-up of drowsiness in the driver.’


Sleeping is a state of rest where a person becomes physically inactive and unaware of their surrounding environment. A driver is classified as asleep if they display a long eyelid closure that is greater than 3 seconds. In the dossier, OEMs must describe their system’s requirements as well as evidence of its ability to detect sleeping drivers.

Unresponsive Driver

Euro NCAP also has a requirement for unresponsive driver state detection to reflect the loss of awareness likely caused by a sudden onset of sickness. For example, if the driver was classified as sleeping and has not responded to any warnings from the ADAS, they would subsequently be classified as unresponsive.

Euro NCAP listed several possible ways to identify an unresponsive driver:

  • They do not return their gaze to the forward road view within 3 seconds of an inattention warning being issued or,
  • A driver whose gaze has been away from the forward road view for longer than 6 seconds or,
  • Has long eyelid closure that is greater than 6 seconds.