A few months ago I was cycling down a bike lane in a 25mph residential area on my way home from work and there were two horses (with riders) side by side in the bike lane (and overflowing a bit outside of it ) - traffic was slow, but fairly dense due to parents picking up kids at the school the road went by. I was a little puzzled what to do as I hear that bikes spook horses, but this was on a street, so I figured that these horses were a bit more accustomed to 'traffic'. Anyway I waited for a gap in traffic and passed using the left side of the lane.

Al