"Slowing down" is holding a flat palm with fingers pointing downwards towards following traffic. I always use my right hand.
It's not universally recognised but if it's used in concert with an action that you're performing at the time (e.g. slowing down) then most people are able to figure it out through the context, assuming they're actually looking at your hands, which they might not be. There's only so much you can do to make things better, but I think this would be a reasonable improvement (it will also force me to slow down sooner as I'll need to coordinate the manouvre and the hand signal).
Edit: NB the Highway Code has it's own signal for stopping / slowing, which is to wave your right arm up and down with the palm open and facing the ground. That's not very practical in traffic and it only ever tends to be used by cyclists in the event of a crash up ahead. The palm-towards-the-back is more compact and practical though not an official signal (more a roadie douchebag signal)
"Slowing down" is holding a flat palm with fingers pointing downwards towards following traffic. I always use my right hand.
It's not universally recognised but if it's used in concert with an action that you're performing at the time (e.g. slowing down) then most people are able to figure it out through the context, assuming they're actually looking at your hands, which they might not be. There's only so much you can do to make things better, but I think this would be a reasonable improvement (it will also force me to slow down sooner as I'll need to coordinate the manouvre and the hand signal).
Edit: NB the Highway Code has it's own signal for stopping / slowing, which is to wave your right arm up and down with the palm open and facing the ground. That's not very practical in traffic and it only ever tends to be used by cyclists in the event of a crash up ahead. The palm-towards-the-back is more compact and practical though not an official signal (more a roadie douchebag signal)