> In order for e.g. a horn to work you need enough time that the driver processes the situation and decides the horn will communicate something AND enough time for the pedestrian or whatever to process that and react to it. Generally it's a lot easier just to press the brake, and more importantly be travelling at a speed and in a manner where the brake is sufficient

I have seen a small kid jump from his father's scooter just when I was overtaking them and they decided to stop because he had seen his grandpa or whoever was that old guy on the other side of the bike lane. His father managed to stop him by grabbing his sweater because I had rung my bell a few seconds before he decided to stop but the kid ended up inches from my bicycle. It was at very low speed, almost walking speed yet hitting a bicycle handlebars head first because you turn around without looking still hurts even if the bicycle his stopped.