When considering the "all traffic on the way" the mapper should naturally only consider legal routes onto the road in question.
Where the intersecting side road is a service road, a driveway, a track or other insignificant entry point to the public highways, traffic entering from such roads does not qualify for consideration of who has passed the priority road sign. (But do check you local legislation, if the traffic sign is valid only up to the next intersection, i.e. whether it refers to "public road" or "any intersection".) Just as any driver who started their journey from a roadside parking spot on the main road, if such parking is available, would not see the sign on the first section.
In countries where the sign does not need to be repeated after every intersection, it can be considered an acceptable interim solution to skip some short minor sideroads (as defined below), on a first pass of mapping these, if the main road has not yet been split for other reasons: even if the side road of an intersection is a public road, but is only a short (50 m at most) dead end stub without any more sideroads branching from it - mainly a public road for few lots only - one can, but doesn't have to, take for granted that the traffic coming from such stubs just previously travelled on the main road and the main road does not need to be split, even if the priority road sign is not repeated after that intersection. But eventually the road will be split at those junctions, too, and the
priority_road tag value amended accordingly.
- priority_road=designated: All traffic on the way has passed a traffic sign designating the road as a priority road, at least before the first intersecting highway. All drivers thus know the side roads will have yield/give way signs. The traffic on this way will not pass a yield/give way sign.
- priority_road=yes_unposted: In countries where the designation as a priority road does not end at the first intersection, sections of roads where some, but not all, traffic has passed a priority road sign. All side roads will have yield/give way sign
- priority_road=end: Traffic entering the way at the start passes an end of priority road sign.
Where the road is not a two carriage way road, and if the signage is present only in one direction, one can use the higher ranking sign for priority_road=* and give the other direction signage as, for example, priority_road:forward=*. For example a way that has priority road sign at one end for the traffic in the direction of the OSM way, but only some of the traffic in the opposite direction has passed a similar sign, would be tagged as priority_road=designated + priority_road:backward=yes_unposted.
Some countries forbid parking on roads designated as a priority road, everywhere or outside (signposted) urban areas. For recording that, see Proposed_features/parking:lane.