I just apply the same rules to filtering that I apply to all other motorcycle use - assume all car drivers are out to kill you and are likely to do the unexpected.
It's a common use in France, and I do that everyday I ride (not really legal) I've learned to look in cars rearview mirror to make sure drivers see me arriving, and make sure not to have too much speed difference with the cars.
If you're going to ride around the 'periphique' you also have to press the horn fequently while making rude gestures. It's a coordination nightmare.
Actually I go further and think everyone is out to kill me including motorcyclists.... I commuted around a very busy part of the M25/M4/M40/northern circular (dependent on the day) for nearly 20 years and I've had car passengers open doors, people swap lanes without indication etc but the closest call was a prat on a motorcycle that pulled out from the front of a truck right into my path. In all that time I never had a collision but that was the closest. The one thing people who are not familiar with filtering may not be aware of is just how mentally tiring it can be. Sometimes I used to just take a break and rejoin the queue to give my brain a rest on the really long delays that I frequently had.
I have to pay tribute to the steel workers of Port Talbot. After I retired I had a part time job on the spanners at an Aprilia and Guzzi dealer in P.T. every evening leaving work with about 1000 cars getting up on to the elevated section of the 2 lane M4 heading west for home, the traffic would be practically stationary for 2-3 miles or more, the drivers would automatically leave a gap down the middle and bikers including myself would be filtering down at 60mph sometime more.
Try riding over the Kingston bridge at rush hour, it's like the wacky races ,, filtering will become 2nd nature, & at times quite enjoyable.
Yeah, I do it when the opportunity presents itself which isnt often here in NI. Only slowly though. Much more often I'll do it at traffic lights, I love doing that, its one of the great advantages of a motorcycle. Funny when you sometimes get a car driver giving you dirty looks thinking your doing something illegal, or maybe its just jealousy.
I only filter when the traffic is at 30 mph or slower and then only 10 to 15 mph faster than the traffic
I've been there. Heading to Scotland on a tour with mates, a junction to the M4 was shut due to an accident and there was a multi-mile long tail back, just filtering between lanes watching every car both sides for signs of a lane swap, it completely frazzled my brain. We got passed by a cruiser with ape hangers and highway pegs zig-zagging around cars and between lanes and I marvelled at the agility he had with such a bike! Filtering was worth the mental effort thought because I bet we easily saved an hour.
Part of my routine was keeping an eye on my mirrors for the fast riders, often they were the couriers. Last thing I wanted to do was hold them up or compete with them.... I wasn't getting paid for the time on my bike unlike them, plus there is no way I could maintain their speed safely.
I remember during the early 80s, I had taken my sick morini to London on the train for weevee to service it, I was left with hardly any time to make it back to Euston, then a helpful bike courier said I will get you there in time,,,,, the most frightening ride of my life,,, we made it with minutes to spare,, took me till Carlisle before I calmed down,,,,,
If I recall correctly, @PatW, Utah's filtering laws are pretty narrow in terms of what's allowed. I think it's mostly just moving forward when traffic is stopped or crawling forward at very slow speeds. I could be wrong on that but depending on how you were filtering that might have been part of the cause of the reactions. Then again, I think some folks just don't like bikes getting ahead of them in line! Or anyone else, for that matter....
@Helmut Visor Your comment about the main hazard is what I'm most concerned about. Initially people won't be expecting bikes to come by them and I've seen drivers do really crazy and unexpected things. So I'll let other riders who choose to filter "train" the drivers for awhile before I give it a go. That said, If there's a blockage due to an accident or something like that, I might be inclined to try it if it seems safe enough. I can definitely see where it could be a very useful part of bike riding.