On a road marked this way, can you drive a light four wheeled vehicle (microcar, quad)?

No. The visible D-9 'motorway' sign marks the start of a road where special traffic rules apply. According to the definition of a motorway, contained in Art. 2 pt. 3 of the Road Traffic Act, traffic by quad bikes (both light and standard) is prohibited on it. A light quad bike, due to its low design speed, would pose a huge threat on a road intended for high-speed traffic.