Is it prohibited to reverse on a one-way road?

In the photo you are driving along a road through fields and you pass on the right a blue sign D-3 "one-way road" and warning sign A-32 "frost on the roadway". The Road Traffic Act does not prohibit reversing on a one-way road - what is prohibited there is making a U-turn, not reversing. The answer is: no.

The Road Traffic Act prohibits reversing a vehicle in a tunnel, on a bridge, on a flyover, on a motorway or on an expressway; a one-way road is not on this list. Reversing is allowed there under the general rules: the driver must give way to other vehicles or road users and exercise particular caution, in particular check that they will not cause danger, and if it is difficult to see the road behind the vehicle, get help from another person. Making a U-turn is a different matter - it is prohibited on a one-way road, because after turning round you would be driving against the flow of traffic. So you reverse slowly, over a short distance, with the reversing light on, looking through the rear window and in the mirrors, and you stop the manoeuvre as soon as someone approaches.

Legal basis: Art. 23 para. 1 point 3 and para. 2 and Art. 22 para. 6 point 1 of the Road Traffic Act (Prawo o ruchu drogowym)