In this overview crossable rest areas in Poland are listed both on A-roads and S-roads. Service stations are called ''Miejsce obsługi podróżnych'' in Polish, which is commonly abbreviated to MOP. The MOPs are announced with signs on the A- and S-roads.
On A-roads without Pedestrian pedestrian tunnel or bridge it is (almost) always required to climb a ± 1m80cm high fence if you want to go on foot to a twin service station on the other side of the road.
This overview is rather up to date.