For those who want to know the halachah, it’s quite simple:
(a) A man is never allowed to gaze at a woman with intent to derive pleasure, even if she is fully covered.
(b) If one tefach (four inches) of a part of her body that should be covered is exposed (e.g. her sleeves end four inches above the elbow), one may not look at her at all, even without intent to derive pleasure.
Why then may a man walk in the street? Only because he has no choice.
(I’m sorry but I don’t have the time to look up all the sources now.)