Origamist said:I am serial under-taker, over-taker and occasional lane-splitter. Filtering is expedient, gratifying, contagious and addictive. Just be careful not to mainline momentum at every opportunity.
Exactly. I do it on the assumption that, at the seriously nasty end of the scale I'll give up some or all of my momentum if there's a chance I could be seriously injured. This includes many of the scenarios described above such as cars turning out from, or in to, side roads (whether you've made eye contact or not). Gaps in the cars invite people to pull in/through. Don't rely on indicators being used or, if they are being used, whether they are truly indicating the driver's intentions.
On the less serious front, it's a calculated risk filtering up the inside of stationary/slow cars if you're within the door zone. I still do it and, to this day, I've managed to avoid it the one time someone did open the door on me (it was someone getting out of a cab where it was an unusual traffic jam). If you don't like doing it, or think it's too risky, then don't do it. I'll also make my decision based on what I know about the lights. If the lights have just changed to red as I approach then I'll happily undertake most things to get to the front. If I'm coming up to them and they've been red for a while then I'll maintain my position within the queue of traffic.
The driver is supposed to be responsible for making sure their passengers do not open the door onto anyone, but that doesn't work in practice, children and cab passengers especially.
It's your duty to do all you can not to hit anyone, this includes pedestrians that wander through stationary traffic (I'll give up some of my momentum if I'm undertaking a vehicle higher than a car, i.e. a bus or a van) if there's a chance there's a pedestrian crossing.
On the aggressive front I'm about middle of the road as far as Londinium cyclists are concerned. Every day I see other riders doing plenty of things that I'd never do (notwithstanding RLJing), and I'm sure someone would look at my riding style and tut furiously (still need to get the helmet cam out again). My motorbike filtering was far more aggressive. Looking back I'm surprised I never had any kind of an accident.
My only specific bits of advice would be (a) perform frequent "lifesaver" checks by looking over your shoulders (I'm constantly surprised how many people change road position without even looking, maybe they're relying purely on their hearing) and then (
