Is it allowed in this situation to turn left?

In the photo you are driving along a wide street in a city whose roadways are separated by a grassy central reservation; on the left, at the entrance of the roadway to the left, there is a round red sign with a white horizontal bar - B-2 "no entry" - and two cars are just coming out of that roadway. Turning left is not allowed here. The answer is: no.

The Regulation on road signs and signals states that sign B-2 "no entry" means that vehicles are not allowed to enter the road or roadway from the side where it is placed. The sign stands at the entrance of the roadway into which a left turn would lead - this roadway is one-way and traffic on it moves towards you, which you can see from the cars coming out, so entering it would mean driving against the flow of traffic, head-on towards the oncoming vehicles. B-2 at the left entrance does not prohibit you from going straight on or turning right. The only exception to the ban is for vehicles shown on a "Nie dotyczy" (does not apply) plate, if there is one, for example bicycles - there is no such plate here. If you want to get to the street on the left, you go straight on or turn right and look for the next junction or a place to make a U-turn, where entering the correct roadway is allowed.

Legal basis: § 17 para. 1 and 2 of the Regulation on road signs and signals