The correct way to deal with Equine traffic is to approach from behind, close the throttle, pull the clutch in at a safe distance, and coast past at just over walking pace, giving the horse and rider plenty of space.
As you pass the rider will probably take a hand off the reigns to give a cheery wave in acknowledgement of your consideration, _this_ is your cue to drop two (or more) gears, wind the loud handle fully open, flip the kill switch a couple of times, and enjoy the impromptu Rodeo taking place in your rear view mirrors as you accelerate safely _out_ of the danger zone well clear of flying hooves...
Extra points are awarded if you're being tailgated by a
4x4 with a "Countryside Alliance", BAFS, CPRE, or "Show
Llama's in Transit" sticker in the window and you manage
to get the horse onto the bonnet :-)
 Race pipe recommended for full effect
J "I change down for horses" G