Is it sufficient not to focus one's gaze on foreign women in the streets and on public transportation, given the difficulty of completely averting one's gaze from dozens of them?

Allah has commanded lowering the gaze, and He does not burden a soul beyond its capacity. It is forbidden to look at the 'awrah (intimate parts) of a non-mahram woman, which is everything except her face and palms, without disagreement. Similarly, it is forbidden to look at her face and palms if there is fear of temptation or with lust. As for the first unintentional glance (a sudden look), there is no blame in it, but one should not follow it with another glance. If a place is such that you cannot lower your gaze therein, then you must not go there unless for a religiously valid need. Men must lower their gaze from non-mahram women except for a legitimate religious purpose, such as giving testimony, medical treatment, or proposing marriage, and this should be only to the extent of the need.