What is the meaning of this black/white (likely non-traffic) sign seen on German highways?

Question

Often I saw this sign at highways in Germany:

Apparently it's not a regular traffic sign, but nevertheless I'm curious about its meaning. I tried to ask a local, but they also didn't know.

Answer 1

These signs are part of a test track for autonomous driving.

The German Wikipedia says in its article about the A9:

Teststrecke für autonomes Fahren

Abschnitte [der A9] in Bayern sollen als Testfeld für Innovationen im Bereich autonomes Fahren und Assistenzsysteme dienen. Das Projekt Digitales Testfeld Autobahn wurde im September 2015 initiiert. Ende 2016 wurden zwischen Pfaffenhofen und Kreuz Holledau spezielle Landmarkenschilder aufgestellt. Diese runden Schilder mit schwarz-weißem Muster dienen der zentimetergenauen Positionsbestimmung durch Kamera-unterstützte Navigation. Insbesondere kann so die Positionsgenauigkeit im regulären Verkehr anhand unabhängiger Fixpunkte gemessen werden.

Translation (using DeepL):

Test track for autonomous driving

Sections [of the A9] in Bavaria are to serve as a testing ground for innovations in the field of autonomous driving and assistance systems. The Digital Test Field Motorway project was initiated in September 2015. At the end of 2016, special landmark signs were installed between Pfaffenhofen and the Holledau junction. These round signs with a black and white pattern are used to determine the position to the centimetre using camera-assisted navigation. In particular, the position accuracy in regular traffic can be measured using independent fixed points.