Bike Riders & Walkers-Dunedin Causeway

I'm a regular walker on the sidewalk on the Causeway and wish people that ride bikes on the sidewalk would let us know when they are passing us.  It is hard to hear their approach with the constant traffic and they come so close sometimes, that if I suddenly stepped sideways to avoid a hole, etc., they would run into me.  Wish we could just get the word out to them to say something like--passing left, etc.