Two separate European requirements govern drowsiness detection in passenger vehicles, and they are routinely confused. One is law. The other is a consumer rating. They set different thresholds, are verified differently, and in January 2026 moved further apart rather than closer together.
What the EU General Safety Regulation requires of a DDAW system
Regulation (EU) 2019/2144 requires every new vehicle of categories M and N sold in the European Union to carry a driver drowsiness and attention warning (DDAW) system. It has applied to all new vehicles since 7 July 2024. Commission Delegated Regulation (EU) 2021/1341 sets the technical requirements and the validation test procedure.12
The General Safety Regulation is type approval legislation. A vehicle that does not meet it cannot be sold. There is no partial credit and no points score.
The timeline
| Requirement | New vehicle types | All new vehicles |
|---|---|---|
| DDAW: driver drowsiness and attention warning | 6 July 2022 | 7 July 2024 |
| ADDW: advanced driver distraction warning | 7 July 2024 | 7 July 2026 |
The requirements engineers most often miss
Four provisions of (EU) 2021/1341 constrain architecture more than the warning threshold does.
- Vehicle systems analysis is mandatory. Point 3.3.2 requires the system to analyse vehicle systems for drowsy driving indicators, and recommends lane position or steering input. A camera-only implementation does not satisfy it.
- No biometric information. Point 2.3.1 requires the system to function in normal operation mode without biometric information, including facial recognition, of any occupant, within a closed-loop system.
- The driver cannot switch it off. Point 3.1.1 prohibits manual deactivation, although the interface warnings may be silenced and must be reactivable in no more actions than silencing took.
- Activation is by speed. The system activates automatically above 70 km/h and must operate normally between 65 km/h and 130 km/h, or the vehicle’s maximum permitted speed, whichever is lower.
The KSS 7 and KSS 8 thresholds, and the alternative the regulation permits
The regulation’s reference measure is the Karolinska Sleepiness Scale (KSS), a 9-point scale on which a person rates their own sleepiness. Point 3.3.1 states:
The DDAW system shall provide a warning to the driver at a level of drowsiness which is equivalent to or above 8 on the reference sleepiness scale set out in the Appendix (Karolinska Sleepiness Scale, hereinafter referred to as ‘KSS’).
The DDAW system may provide a warning to the driver at a level of drowsiness which is equivalent to level 7 on KSS.
Commission Delegated Regulation (EU) 2021/1341, Part 1, point 3.3.1
So KSS 8 is mandatory and KSS 7 is optional. What matters more is the phrase equivalent to. The regulation does not require a manufacturer to run a KSS study. Part 2, point 5.2 permits alternative measurements that directly monitor the participant’s state (electroencephalography and PERCLOS are named as examples) and requires that:
the manufacturer shall provide evidence that the chosen measurement is a valid and accurate means to assess driver drowsiness, and that the drowsiness threshold used in the validation testing is equivalent to a KSS level referred to in point 3.3.1. of Part 1.
Commission Delegated Regulation (EU) 2021/1341, Part 2, point 5.2
That is the entire test for an alternative ground truth: valid, accurate, and demonstrably equivalent to the KSS threshold. Point 6 adds the arithmetic for translating a scale with different granularity onto the KSS.
The reason to take that route is that the KSS is a poor instrument for this job. It is a self-report of tiredness, a subjective feeling, rather than a measure of impairment, the increase in relative risk of a performance failure. Collecting it requires interrupting the participant every five minutes or so once they first report a KSS of 6 or above, which rouses the person whose drowsiness is being measured. In a 2023 closed-track study, the KSS predicted lane departures with three times the errors of an objective eyelid measure, the Johns Drowsiness Scale (JDS™).6
Two further weaknesses matter for anyone selecting a ground truth. The KSS and an objective impairment measure sometimes decouple: a participant may report a high KSS while unimpaired, or a low KSS while impaired, because the two are measuring different things. And the act of asking is itself an intervention: rousing a participant counteracts drowsiness, so the measurement interferes with the state it is trying to capture.
Mapping the regulatory thresholds to an objective scale
The Johns Drowsiness Scale (JDS™) scores impairment from drowsiness on a 0 to 10 scale, derived from the movements of the eyelids and updated every minute. Because it is continuous and objective, it can be recorded throughout a validation drive without interacting with the participant. Optalert’s validation dataset establishes a direct, linear relationship between the two scales, with a 95% confidence interval.
| Regulatory threshold | Status under (EU) 2021/1341 | KSS level | Equivalent JDS |
|---|---|---|---|
| Early warning | Permitted, not required | 7 | 4.3 |
| Warning | Mandatory | 8 | 5.9 |
Read alongside point 5.2, that is what a technical service needs: a stated threshold, and evidence of its equivalency to the KSS level in point 3.3.1. Four European technical services operating Euro NCAP accredited laboratories: UTAC, Applus+ IDIADA, TÜV Rheinland, and a UK-based technical service: have reviewed that evidence and confirmed the JDS as a valid alternative to the KSS under the regulation. Because Euro NCAP’s 2026 Driver Monitoring assessment is itself built on (EU) 2021/1341, those confirmations apply to the rating protocol as well as to type approval.
Euro NCAP is not type approval, and in 2026 the two diverged
The European New Car Assessment Programme is a consumer information organisation. It is not a regulator, it does not grant type approval, and a vehicle that scores poorly can still be sold lawfully. It awards points, and those points produce a star rating manufacturers care about commercially, because many consumers factor it into their purchasing decisions.
What changed in January 2026
Euro NCAP replaced its rating scheme in January 2026: the largest revision since the overall star rating was introduced in 2009. The four assessment boxes that older material describes, Adult Occupant Protection, Child Occupant Protection, Pedestrian Protection, and Safety Assist, no longer exist. In their place are four stages, each scored out of 100: Safe Driving, Crash Avoidance, Crash Protection, and Post-Crash Safety.4
A vehicle must reach the balance threshold in every stage, so a weak stage still caps the result. For five stars that threshold is 80%, with a soft landing in the first two years: in 2026 Safe Driving is 60% and Crash Avoidance 70%, rising to 70% and 80% in 2027.
Where drowsiness now sits, and what it is worth
Driver monitoring has moved into Safe Driving, under the Driver Engagement element, and is worth 25 of the 100 Safe Driving points: a substantial increase in weight over the old Occupant Status Monitoring category.
| Driver Monitoring element | Points |
|---|---|
| Transient states (long distraction, short distraction, phone use) | 15 |
| Non-transient impairment: drowsiness | 2 |
| Non-transient impairment: “non-fatigue related” (alcohol, drugs) | 2 |
| Non-transient: microsleep | 2 |
| Non-transient: sleep | 2 |
| Non-transient: unresponsive driver | 2 |
| Total | 25 |
The protocol’s own terminology has shifted. The 2022 version treated fatigue as the umbrella term, with drowsiness, microsleep, and sleep as its three stages. The 2026 version treats impairment as the umbrella and separates drowsiness from what it calls, verbatim, “non-fatigue related” impairment. The distinction Optalert has argued for is now built into the assessment structure.
The threshold Euro NCAP applies
The protocol states that systems capable of detecting a driver reaching “a KSS level >7 at the latest, or an equivalent metric appropriate to assess risky levels of drowsiness” are eligible to score points, and that the system shall be functional from 50 km/h.5 A learning period of up to 10 minutes at 50 km/h or above is permitted from the start of each journey. Three consequences follow.
- Euro NCAP admits an equivalent metric, as the regulation does. A validated objective scale is acceptable to both, and the evidence package is the same package.
- The detection point is earlier than the regulation’s. Euro NCAP sets KSS above 7 as the latest acceptable detection point, so a system tuned only to the type approval minimum is tuned to the wrong target for the rating.
- Speed bands differ. The regulation activates DDAW above 70 km/h. Euro NCAP requires impairment detection from 50 km/h, and the other driver states from 20 km/h.
How the two are verified
| EU GSR type approval | Euro NCAP | |
|---|---|---|
| Legal status | Mandatory. The vehicle cannot be sold without it | Voluntary consumer rating |
| Instrument | (EU) 2019/2144 and (EU) 2021/1341 | Published assessment protocols, revised on an announced cycle |
| Drowsiness threshold | Warning at KSS 8 or equivalent; KSS 7 permitted | Detection by KSS above 7 at the latest, or an equivalent metric |
| Outcome | Pass or fail | Points, contributing to a star rating |
| Verification | Manufacturer validation testing, assessed by a technical service against a prescribed protocol | Manufacturer dossier reviewed by the Euro NCAP Secretariat, with laboratory spot checks |
| Stability | Not amended since it applied in July 2022 | Revised regularly; the scheme changed in January 2026 |
A compliance pathway
The order of work matters: The human validation study is the expensive step, and the one most often repeated unnecessarily.
- Choose the ground truth before designing the study. If an objective alternative to the KSS is used, the equivalency evidence required by point 5.2 must exist before validation begins. Retrofitting it afterwards is the costly path.
- Confirm the architecture meets the non-threshold requirements. Vehicle systems analysis, the absence of biometric processing, deactivation behaviour, failure warning, and the roadworthiness provisions in point 3.6 are type approval requirements independent of detection accuracy.
- Build the validation sample to the regulation, not to convenience. At least 10 participants, none involved in developing the system, at least 10 true positive and false negative events combined, and at least one true positive in each of day and night conditions.
- Know the acceptance criterion. A DDAW system is deemed effective where average sensitivity across participants exceeds 40%, or the lower bound of the 90% confidence interval exceeds 20%. Both figures shift where the assessment interval exceeds 15 minutes or the test is run on open road.
- Design to the Euro NCAP threshold and satisfy the regulation as a subset. Detecting earlier than KSS 8 covers type approval and earns the rating points. Detecting only at KSS 8 forfeits them.
- Cover the noise variables in the Euro NCAP dossier. Demonstrated function is required across driver age, sex, stature, Fitzpatrick skin type 1 to 6, eyelid aperture from 6.0 mm to 12.0 mm, lighting from 100,000 lux to 1 lux, eyewear, facial hair, and facial occlusion.
- Treat microsleep, sleep, and unresponsive driver as separate deliverables. Each carries its own Euro NCAP points and its own definition: a 1 to 2 second eye closure, a closure of 3 seconds or more, and either a gaze that does not return within 3 seconds of a distraction warning or eyes closed for 6 seconds or more.
Frequently asked questions
What is DDAW under the EU General Safety Regulation?
DDAW stands for driver drowsiness and attention warning. Regulation (EU) 2019/2144 requires a DDAW system in all new vehicles of categories M and N sold in the European Union, applying to new vehicle types from 6 July 2022 and to all new vehicles from 7 July 2024. Commission Delegated Regulation (EU) 2021/1341 sets the technical requirements and validation procedure.
At what KSS level must a DDAW system warn the driver?
At a level of drowsiness equivalent to or above 8 on the Karolinska Sleepiness Scale. A warning at KSS 7 is permitted but not required. The regulation specifies equivalence rather than the scale itself, so an alternative measure may be used.
Does the EU GSR require the Karolinska Sleepiness Scale to be used?
No. Part 2, point 5.2 of (EU) 2021/1341 permits alternative measurements that directly monitor the participant’s state, provided the manufacturer supplies evidence that the measurement is a valid and accurate means of assessing driver drowsiness and that the threshold used is equivalent to the KSS level in point 3.3.1.
What is the difference between EU GSR compliance and a Euro NCAP rating?
The General Safety Regulation is type approval law: a vehicle that does not meet it cannot be sold in the European Union, and the outcome is pass or fail. Euro NCAP is a voluntary consumer rating that awards points toward a star rating. They set different drowsiness thresholds and verify them differently, so one does not satisfy the other.
How does Euro NCAP assess drowsiness detection in 2026?
Under the scheme implemented in January 2026, driver monitoring sits within the Safe Driving stage and is worth 25 points. Drowsiness detection carries 2 points, with a further 2 each for microsleep, sleep, unresponsive driver, and impairment unrelated to drowsiness. Systems must detect a driver reaching a KSS level above 7 at the latest, or an equivalent metric, and be functional from 50 km/h.
What KSS value does a JDS score correspond to?
KSS 7 corresponds to a JDS of 4.3 and KSS 8 to a JDS of 5.9, established with a 95% confidence interval across Optalert’s validation dataset. These are the two thresholds named in (EU) 2021/1341, which allows a DDAW system to be validated against an objective eyelid measure rather than a self-report study.
References
- Regulation (EU) 2019/2144 on type-approval requirements for motor vehicles. EUR-Lex.
- Commission Delegated Regulation (EU) 2021/1341 of 23 April 2021, driver drowsiness and attention warning systems. EUR-Lex.
- Commission Delegated Regulation (EU) 2023/2590 of 13 July 2023, advanced driver distraction warning systems. EUR-Lex.
- Euro NCAP. Overall Assessment Protocol, v10.0, June 2025, implementation January 2026. euroncap.com.
- Euro NCAP. Safe Driving: Driver Engagement Protocol, v1.1, October 2025, implementation January 2026. euroncap.com.
- Cori JM, Wilkinson VE, Soleimanloo SS, Westlake J, Stevens B, Rajaratnam SMW, Howard ME. A brief assessment of eye blink drowsiness immediately prior to or following driving detects drowsiness related driving impairment. J Sleep Res. 2023 Jun;32(3):e13785. doi:10.1111/jsr.13785. PMID: 36478313.
Designing for the threshold that moves
The type approval requirement has been stable since July 2022 and remains unamended. The rating has not been: Euro NCAP publishes protocol changes on an announced cycle. A system validated against a fixed, objective measure of impairment can be re-evidenced against a new threshold without a new human study. A system validated against a self-report scale cannot.
Contact Optalert to discuss validating your DDAW system against the Johns Drowsiness Scale, or to request the equivalency evidence a technical service will ask for.
