In the situation presented, are you entitled to drive through the level crossing without stopping, if there is no rail vehicle approaching?

In the photo you are approaching a level crossing over an electrified line; the barriers are raised, sign B-20 "STOP" is on the right, and a dark car is coming from the opposite direction. You are not allowed to drive over the crossing without stopping, even if no rail vehicle is approaching - the STOP sign always requires you to stop. The answer is: no.

The Regulation on road signs and signals states that sign B-20 means no entry to the junction without stopping, and this rule applies accordingly to sign B-20 placed in front of the tracks of rail vehicles; the Road Traffic Act also requires you to make sure, before entering the tracks, that no rail vehicle is approaching. Stopping does not depend on your judgement of whether a train is coming - its purpose is precisely to give you time to calmly look both ways and listen, because a train is quiet and fast, and the view along the tracks is sometimes blocked. You stop in front of the STOP sign, look left and right, and when the tracks are clear, you drive across without stopping on them.

Legal basis: § 21 para. 1 and 4 of the Regulation on road signs and signals; Art. 28 para. 1 of the Road Traffic Act (Prawo o ruchu drogowym)