Study of ring road type (Belgium)
List from http://en.wikipedia.org/wiki/List_of_motorways_in_Belgium#Ring_roads_.28R.29
Main
R0 - Brussels (outer ring) - Freeway R1 - Antwerp (inner ring) - R2 - Antwerp (outer ring) - R3 - Charleroi (outer ring) - Freeway R4 - Ghent (outer ring) - Freeway R5 - Mons - Freeway R6 - Mechelen - R7 - Liège - R8 - Kortrijk - 75% Freeway - 25% Major Highway R9 - Charleroi (inner ring) - Freeway
Antwerp
R10 - Antwerp (inner ring) R11 - Antwerp (second outer ring) R12 - Mechelen (inner ring) R13 - Turnhout R14 - Geel R15 - Herentals R16 - Lier
Brabant
Former province of Brabant, corresponds to Flemish Brabant, Walloon Brabant and the Brussels-Capital Region nowadays.
R20 - Small ring of Brussels R21 - Intermediate Ring of Brussels R22 - Greater ring or second ring of Brussels R23 - Leuven R24 - Nivelles R25 - Aarschot R26 - Diest R27 - Tienen
West Flanders
R30 - Brugge R31 - Oostende R32 - Roeselare R33 - Poperinge R34 - Torhout R35 - Waregem R36 - Kortrijk
East Flanders
R40 - Ghent (inner ring) - Major Highway R41 - Aalst R42 - Sint-Niklaas R43 - Eeklo
Hainaut
R50 - Mons (inner ring) - Major Highway R51 - Charleroi (inner ring) R52 - Tournai R53 - Châtelet R54 - La Louvière R55 - Chimay
Liège
R61 - Verviers R62 - Hannut
Limburg
R70 - Hasselt (inner ring) R71 - Hasselt (outer ring) R72 - Tongeren R73 - Bree