In this situation, can you resign from using the indicator when changing lanes?

In the photo you are driving on a dual carriageway between noise barriers; your right lane is ending, and a lane-change arrow pointing to the left lane has been painted on the roadway. You are not allowed to skip using the indicator when changing lanes. The answer is: no.

The Road Traffic Act requires a driver to signal the intention to change direction or lane with the indicator clearly and in good time, and to stop signalling immediately after completing the manoeuvre. The Regulation on road signs and signals states that the lane-change arrow P-9 means an order to move into the neighbouring lane shown by the arrow. The fact that the lane change is forced by the end of the lane does not free you from signalling - drivers in the left lane must know at what moment you intend to merge, and if several vehicles are driving behind you, the indicator helps to set the order in which vehicles merge. You switch it on in good time, check the mirror and the blind spot, give way to vehicles in the left lane and move over smoothly; in a traffic jam the zipper merge (jazda na suwak) applies and the driver in the left lane lets you in directly before the end of your lane. You switch off the indicator immediately after changing lanes.

Legal basis: Art. 22 para. 4, 4a and 5 of the Road Traffic Act (Prawo o ruchu drogowym); § 87 para. 3 of the Regulation on road signs and signals