Originally Posted by
'nother
It is hard to say whether visibility was an issue with the guys up on Skyline but I would have a hard time believing someone who said they "couldn't see" a group of 4 guys with multi-colored outfits on moving at 30+ MPH. It is a lot easier to believe that they thought they could make the turn ahead of the riders, but misjudged the approaching cyclists' speed and failed to yield to them.
I live in those mountains, and can attest that bicyclists when in the shadows created by the trees can be hard to see - especially from cars that happen to be in a clearing of sunlight. While riding on Skyline on a silver bike and wearing a red jersey with "reflective accents", my own wife walking towards me didn't see me until I was quite close, surprising her. Since then I've always use front and rear lights, even in daylight.
In shadows on the side of the road, bicyclists are hard to see.
And yes, even if seen, many drivers will not properly judge the speed of a two-wheeler. The left hand turn in front of oncoming two-wheelers is the most common motorcycle accident as well, btw (and they always have their very bright - compared to any bicycle - headlight on). The MSF (Motorcycle Safety Foundation, what most people in CA take to get their license) class teaches about riding defensively, when to suspect you might not be being seen, etc.