These are the codes used to "define a ride difficulty."

Speed ratings:

AA: Over 22 mph

A: 19-22 mph advanced pace with few stops.

B: 16-19 mph vigorous pace with occasional stops.

C: 13-16 mph steady pace, rest stops every hour.

D: 10-13 mph sightseeing pace, semi-frequent stops at key points to wait for riders.

E: Under 10 mph relaxed pace, frequent stops to wait for everyone.

MBR: Mountain Bike Ride

Terrain ratings:

1. Multiple long and/or steep climbs

2. Multiple and/or large hills

3. Rolling with some hills.

4. Generally flat or rolling.

Ride Rating Example:  

D/4/30 = a 30 mile, 10-13 mph ride over flat terrain