We don't filter around cars, we move in very large bunches that act as 1 vehicle, this increases our visability, as such, if the front of a bunch has gone through a green light, the rest will keep going even if the light goes red. we do not then filter around cars as there cannot physically be a car in front of us, we have used our lane and the car wouyld have to wipe out about 50 cyclists to enter our lane (this has happened before). Cars complain that we ride to closely together, i realise we are suppost to leave 1m to the next cyclist but this would halve our speed and triple our length (ie. we would take up 180 Metres of lane instead of 60). My bunch is not "really going for it" yet we maintain a speed above 50km/h, we have been clocked by police in excess of 120km/h. this means cars complaining that we are slow is not valid as we are capable of speed just as high as them. we often ride the last 15km of our ride nat a min speed of 80 km/h in an 80km/h zone. I will admit that cycle couriers do filter through traffic but we start our ride just before sunrise and are off the road by 9am, i actually have time to have a shower before attending church on a sunday morning.