Case in point, I saw a cyclist split lanes on 15th St. in Denver going west. This is on a relatively steep hill and has about a 40 degree two lane turn with a light in the middle of the hill and the guy was filtering to the front of the line between the traffic lanes (not on the right). When he was about 4 cars from the light, the light turned green and everyone went. He was too slow to accelerate with the cars (it is a steep hill) and the road really too narrow for 2 lanes, much less a cyclist splitting those two lanes. He came very close to be squashed between the turning cars and had no escape route. It was a boneheaded maneuver. This road is narrow enough...and steep enough that filtering on the right side between the traffic lane and the parked cars isn't really a good idea.