At what speed are you allowed to drive a passenger car with a trailer on the road beyond this sign?

Why?

The visible D-9 motorway sign shows that you are entering a motorway. A passenger car towing a trailer is a vehicle combination, with a motorway speed limit of 80 km/h. The 70 km/h limit applies to that combination on an ordinary single-carriageway road outside a built-up area, while 140 km/h applies to a passenger car without a trailer on a motorway.

art. 20 ust. 3 pkt 2 lit. a Prawa o ruchu drogowym