Are you obliged to exercise extreme caution at all times when driving in a residential zone?

In the photo, in winter, you are entering a small housing estate street marked with sign D-40 "residential area". When driving in a residential area, you do not have a statutory duty to exercise particular caution all the time. The answer is: no.

The Road Traffic Act distinguishes between ordinary caution, which applies always, and particular caution, which you exercise only when the Act requires it - for example when approaching a junction, a pedestrian crossing or a level crossing, when overtaking or reversing, or when driving in reduced visibility. The rules on residential areas do not contain such a requirement; instead they set firm rules: a speed of no more than 20 km/h, right of way for pedestrians, who may use the whole width of the road, parking only in marked places, and leaving the area is treated as joining traffic (włączanie się do ruchu). Sign D-40 also informs you that speed bumps and other traffic calming devices might not be marked with warning signs. In practice the difference is small: 20 km/h and children playing require full attention, and particular caution still applies in specific places in the area, for example at junctions.

Legal basis: Art. 3 para. 1, Art. 11 para. 5, Art. 20 para. 2, Art. 49 para. 2 point 4 and Art. 17 para. 1 point 1 of the Road Traffic Act (Prawo o ruchu drogowym); § 58 para. 1 and 2 of the Regulation on road signs and signals