People can pick up a lot of information from someone they see walking towards them. They can tell by your gait, your body movements, and facial expressions (if you're close enough to see them) whether you might be a threat or not. As a man in this situation who has never and will never be a threat to women I think that comes across in subtle ways without having to say a word. And since someone I didn't know at a party came up to me and said I had the kindest face they've ever seen, that also works in my favor. When we finally pass each other I always say hello and smile and keep on walking. And if you do see a woman walking towards you don't do anything stupid like slow down or stop or walk with your head down with your hands in your pockets.