In this situation, can you use an audible warning signal when you see pedestrians walking on the road?

Why?

The D-40 sign on the right marks a residential zone, where pedestrians may use the full width of the road and have priority over vehicles. Their presence on the roadway alone does not justify sounding the horn. The horn is for warning of danger, not for making pedestrians move out of a car's way.

art. 11 ust. 5 oraz art. 29 ust. 1 i ust. 2 Prawa o ruchu drogowym