For ring expressways, the designations A20, A30, A40, etc., were used. For expressways connecting to other provinces which already had national designations (beginning with the letter G), designations with the letter A were attached.
In the context of ring expressways, designations like A20, A30, and so on were used. When connecting to existing provincial expressways that had a national designation starting with "G," an "A" was added to the designation.