The load-bearing model levels of ductile iron manhole covers

How to distinguish the load-bearing model grades of ductile iron manhole covers and what areas are they used for?

The load-bearing model levels of ductile iron manhole covers are divided into six categories as follows:

 (A15 type): green belts, sidewalks and other areas where motor vehicles are prohibited from entering.

A15 grade ductile iron manhole cover

(B125 type): sidewalks, non-motorized vehicle lanes, car parking lots and underground parking lots.

(C250 type): residential quarters, back streets and alleys, areas where only light motor vehicles or small cars run, within 0.5m of curbs on both sides of the road.

C250 manhole cover

(D400 type): urban arterial roads, highways, high-grade highways, expressways and other areas.

D400  cover and frame

(E600 type): freight stations, docks, airports and other areas.

 (F900 type): airport runways and other areas.