I'm aware of that system, but don't find it very useful, for the following reasons. 1) Many people don't know what A/AA is, having never been on anything that hard. Therefore, they are inclined to rate things up. This is potentially true of any rating system, but the better spelled out it is, the more likely to have consistent ratings. 2) It doesn't take into account exposure and navigation issues. For example, a ride I'd like to do starts in Green River, Utah, and heads up to Rangely, CO. It has probably 6000 possible wrong turns, and no towns or gas down any of them, so you better get it right or have a 400 mile range. However, there is nothing more than B difficulty on your scale (but it obviously isn't a novice friendly route). I think it's important to differentiate since so many D/S type rides have this issue. 3) It doesn't take into account the duration of difficulty (neither does TWN in the current form). Some rides I've seen with that rating had one spot that correctly bumped a ride from C to A, but were boring otherwise. It would be nice to differentiate, because a more novice rider might be willing to attempt a B route with a short A section they can get their buddies to help them through, vs. a route that's all A and they shouldn't be there. I like T and N, but I'm not sold on W (there's very few places you can't get a GS if you are willing to try hard enough), and I wish there was a proxy for time and/or sustained level of difficulty, to help with planning. I think F could be a note that follows rather than an abbreviation- like a 5.9 crack climb, vs. a 5.9 slab. So, a proposal: T as it stands S 1-3 where 1 = the same throughout (ie, a T4 from start to finish is T4S1, whereas an easyish ride with one tough spot in the middle is T4S3). N as it stands Feature note Rereading, that S thing needs some work, it's not clear as it stands.