Does this road sign warn of the beginning of the stretch of road where the average speed is controlled and recorded by a stationary recording device?

In the video you are driving on a dual carriageway outside town; on both sides there are blue signs with a symbol of a camera and lanes - D-51a "automatic average speed check". The sign warns of the beginning of a stretch of road where the average speed is checked and recorded by a stationary recording device. The answer is: yes.

The Regulation on road signs and signals states that sign D-51a "automatic average speed check" warns of the beginning of a stretch of road where the average driving speed is checked and recorded by a stationary recording device, and sign D-51b informs about the end of such a stretch; the ordinary D-51 "automatic speed check" warns of a single speed camera. Average speed checks work differently from a speed camera: cameras at the beginning and at the end of the stretch read the number plate and the travel time, and the system calculates the average speed - you cannot "trick" it by braking before the camera, because the whole stretch counts, and it is often several kilometres long. Beyond the sign, you drive at a speed no higher than the limit on this road for the whole stretch, up to sign D-51b. Covering part of the stretch extremely fast and slowing down later does not help if the average exceeds the limit. The notice comes by post to the owner of the vehicle.

Legal basis: § 60b para. 1-3 of the Regulation on road signs and signals