In this situation, when turning left at the nearest intersection are you entering a no through road?

In the photo, you are driving along a dual carriageway on the edge of a town, next to a forest on the right; before the junction there is a blue sign with a road layout, on which the intersecting road to the left ends with a red bar - D-4b "entry to a no through road". If you turn left at the nearest junction, you will enter a no through road. The answer is: yes.

The Regulation on road signs and signals states that sign D-4b "entry to a no through road" means that the road beyond the junction on the side shown on the sign is a no through road, and sign D-4a "no through road" marks the beginning of such a road. You read the symbol on the sign like a map: the thick line is the road you are driving on, the branch is the intersecting road, and the red crossbar at its end means there is no way through further on. Here the branch leads to the left, so if you turn left, you will drive into a dead end and will have to make a U-turn or reverse. The sign is for information - it does not prohibit entry, but it saves you from getting lost. If there is a plate under the sign with a bicycle symbol and the words "Nie dotyczy" (does not apply), it means that you can get through there by bicycle, though not by car.

Legal basis: § 45 para. 1-3 of the Regulation on road signs and signals