With what maximum permissible speed can you drive a tram on single carriageway with one traffic lane in each direction, marked with this sign?

In the photo we see sign D-43 "end of built-up area" - a white board with the outline of a town crossed out with a red line. When driving a tram on a single-carriageway road with one lane in each direction, beyond this sign you may drive at a speed of no more than 70 km/h - the answer is B.

Outside a built-up area, the Road Traffic Act sets the speed separately for passenger cars, motorcycles and lighter lorries, and separately for other vehicles. A tram does not belong to the first group, so the limits for vehicles not listed there apply to it: 80 km/h on dual carriageways with at least two lanes in each direction, and 70 km/h on other roads. A single-carriageway road with one lane in each direction is one of these other roads, so 60 km/h (answer A) is too low, and 80 km/h (answer C) is too high.

Legal basis: Art. 20 para. 3 point 2 of the Road Traffic Act (Prawo o ruchu drogowym); § 58 para. 3 of the Regulation on road signs and signals