Originally Posted by
Lightning Pilot
The more serious or dedicated riders who participate in cycling events understand, and "on your left" is fairly intuitive, but the verb conveys a complete thought, where as "on your left" could mean anything to the casual rider or pedestrian, causing the immediate thought, and confusion, of "What's on my left?"
For some reason, I think some people are interpreting "on your left" to be "go to your left" instead of "don't go left". My sense is that occurs because it isn't clear whether it's supposed to be an instruction to them or a statement of the passer's position, so they hear it as "go on your left".