Presentation on maintaining effective drowsiness monitoring when Driver Control Assistance System (DCAS) is active. A DDAW system using indirect means cannot effectively assess driver drowsiness when the driver is not nominally required to steer, brake, or accelerate. Hands-on or eyes-on engagement does not establish alertness. Either the DDAW system or an alternate system should meet prescribed DDAW system performance while DCAS is active, with no gap in coverage or performance. UN R171 02 series amendments do not prescribe DDAW-equivalent performance criteria for drowsiness determination.