Originally Posted by Maelstrom
They do in bc.
But really to take that world wide would require pics and stuff. Difficulty is subjective.
Green - Easy as pie. Usually smooth with no steep climbs or descents. Usually a double track
Blue - single track. Not very technical, no stunts, pretty groomed with roots and rocks. This is typically like most xc courses with lung busting climbs. Can have some basic stunts.
Black - single track. Steep technical descents. Usually nothing that can't be walked. But still very difficult for average riders This is usually a typical dh level type run. A true big mountain experience. Can also have some stunts and skinnies that are highish and narrow.
Double Black - Creme de la creme. High skinny stunts, big drops or REALLY steep lines. This requires, nuts, skills and a good bike.
Thats more or less how bc breaks it down.
I did our local trail map. I was SHOCKED when I looked for a trail rating system on IMBA and found none. I fell back on the ski system.
One thing to remember about the SKI system though is that it is proportionate to the local terrain. So a small resort in Michigan may have a double black diamond that an intermediate can ride (it's regional). But a double black in Colorado may be likely to demolish that same intermediate rider.