Originally posted by mechBgon
Least able to do either one? Why...? Because he/she is riding beyond his/her stopping distance, perhaps? 
The uphill rider is not the one making the situation potentially hazardous, and therefore should not bear the primary burden of eliminating the hazard IMHO. Or is it my problem that the other rider is reckless?
The downhill rider is least able to do either one due to momentum and gravity pulling them down the hill. The downhill rider is going to take longer to stop than the uphill rider, even if all else is equal and they are moving at the same speed initially.
In the collision that sent me to the hospital, I could have stopped completely and it wouldn't have saved me. Ironically, I was fully aware of the potential for a collision at that spot, and was watching intently for oncoming riders on the trail... but at a closing speed of about 30 miles per hour (5mph for me, 25mph for him) there was no way I could get out of the way... no time to react. Gee, I guess it's my fault, huh?
No, it's not your fault -- the other rider was obviously not taking the proper care to make sure he could stop in time for any obstacles or riders he might meet on the way down. I'm not trying to excuse reckless riding -- if I've failed to make it clear earlier I'll say it again. The original question I resonded to simply asked "whose right of way is it?" and my arguments have been based on the assumption (yeah, yeah -- I know) that both riders are riding responsibly -- if someone is riding like a maniac then all bets are off. My argument is that in the case where both riders can see each other and both could stop in time, the uphill rider should give the right of way if he can.
Test out your theory sometime. Start climbing a singletrack ascent on a hillside trail that puts you in your granny gear. Have a friend descend at 20-25mph down the trail toward you. See for yourself whether it's easy to get out of the way when your friend explodes through the brush. Where are you supposed to go? Just fall off the trail to the downhill side? Unclip, jump up the bank and haul your bike up after you?
Well, where do you expect the downhill rider to go? Seems like he would have the same problem (oncoming rider, trail blocked) but fewer evasive options since some of the low-speed manuevers are N/A when going down the hill at speed, and he'll be at a disadvantage in stopping or turning due to momentum and gravity. In fact, in your example above the downhill rider would be at a disadvantage even if you both were going the same slow 5 MPH because it would take him longer to stop. Again, all of this presupposes that the downhill rider is not over-riding the trail and that he can safely stop when he sees something in the trail.
Look, obviously the most important thing is that all riders watch where they're going and make sure they don't become a hazard to others. As long as riders do that, then the question of who has the right-of-way is pretty much moot, isn't it?
