Originally Posted by Helmet Head
I'm all for being predictable, but how can you be predictable to someone who doesn't know you're there, which is pretty much the case when you're filtering forward?
This is a good question. You never want to put yourself in the blind spot of a moving vehicle, or in other words, you must always remain consipcuous. A moving vehicle can move freely within it's lane, which can squeeze a cyclist into a curb or other road hazard.
But nothing is black and white about filtering. You have to use your judgement. If you don't know when it's safe and when it's not, just don't do it.
For example, a gray issue for me is sidewalk riding. I don't do it as a rule, but sometimes I can defeat a traffic jam safely by hopping onto the sidewalk on my MTB.