This is always a scary situation for me. My first instinct is to pass as quickly as possible when it can be done safely with a full view of the trail ahead. Problem here comes in with a tall sled (M-10) and a lot of power (800 XCR). Most of the time I feel guilty about the roost coming from behind my sled, so I'm cautious, but I really don't know that my presence is known, and am not sure that the person is not about to swerve to miss a bump or something (don't ask me why I think like that). I've tried the approach of coming up close behind the person to be passed, and blipping the throttle, but it doesn't work well for me. Maybe my sled is too quiet, I don't know. Plus, I'm nervous about being that close, even at 15 or 20 mph.
If I know the trail well, and I know an intersection is close by,
I usually wait. Problems with this approach too. Many people
stop at the intersection, then blast through it, without knowing that someone has been patiently following for the last 5 minutes. (Group leaders - kindly check to see the last machine in the group is yours, for Pete's sake!
Last weekend I was out for a while and came up on a couple of sleds running at maybe 20 to 30mph. I wasn't in any hurry, but would like to have been running a little faster, so I followed patiently. The guy in back finally caught me out of the corner of his eye going around a corner following at a safe distance. He slowed and let me by with a casual wave of his hand, which I returned. A nice, easy, casual, pass, done in a professional manner. His buddy was a different story.
The section of trail we were in was kind of tight, so I had no choice but to follow patiently. We were coming up on an intersection soon, so I just enjoyed the scenery. When we got to the intersection, he stopped, turned around on his sled, and looked straight at me. Cool, I thought, and expected him to go through the intersection and allow me past on the other side (I was solo). NOT! The jerk continued on, only at a slightly faster pace. There was no way he could have confused me on my black sled for his buddy on a green one.
Sorry folks, this situation has just been interpeted as an informal challenge. Was he thinking that I had just joined him and his buddy as a third member of his group- riding in the middle of it? There was a staight section of trail coming up, and when we got there the coast was clear, so I took full advantage of it. Wasn't much of a contest. He was now the proud owner of a lap full of wet snow, and I felt no guilt.
Both of these sleds were equipped with rearview mirrors, but not riders that were using them. Mirrors should be standard equipment on any sled using the trail systems. Maybe then people will actually learn to use them. If you are using them, you can still be caught by surprise, but not nearly as often.
The sleds I pass, I try to treat as if my kid sister were the driver. From there on it's a judgement call, each situation is different. Sometimes there is no clear right or wrong. I ride in a very popular area, and when conditions are favorable, there are several hundred rental sleds on the trails. God only knows who is on the sled in front of you.