For crashes at junctions which cannot clearly be allocated to one specific road, the class of the main road is entered. The main road is defined as the road which has priority. For roundabouts and signal controlled junctions, the main road is the one with the highest class of all the roads entering the junction. If roads are of equal class then the road with the lowest number is taken as the main road.
Service roads are recorded as Unclassified, not with the class of the main road alongside which they run.
Individual highways authorities can determine whether they wish to classify C roads separately from Unclassified roads. For this reason, this distinction cannot be relied upon nationwide.