Usually they don't see you and with road tires, they definitely don't hear you. You have to let the know you're around soon enough that you can dodge their dumb moves.
They need time to
1] be ware of you,
2] decide on an action,
3] take an action, and
you need time to
4] decide on an action
5] take an action.
When you break it down, you can see there has to be a long time sequence between the start of the sequence and the end. Peds don't like surprises any more than we do. Visual clues I have not found to be effective. Bright yellow moving at them is ignored. Definitely need an unusual alert. Most effective is audio communication and you hope they aren't deaf.
1. bell [ problem is many will not associate this sound with bike until too late ]
2. "coming thru", "on your left", "look out", "hello", etc
3. zsounds truck type air horn. [ problem is not first reaction. They will jump out of way, but second. I jumped away from a semi and you're just a bike. ugh...]
I have bell, but found voice to be best solution for peds. Later plan to get zsounds air horn for drivers on cell phones.