guys! We have web-portal and there is a filter "near subway station ...". So I am curious about what "near subway station" means specifically for you? 50m, 100m, 1km, 2km, 10km and so on? Thanks for your feedback!
I think this will depend on the general availability of subway stations for your users. In general how many subway stations exist within a 50km radius? If several, then 50km could serve as "near" for the users.
"Near" should serve the purpose of showing the "n" closest stations. You certainly don't want 0 to be the result, and ideally would not want more than 5-10. A study of the distance between subway stations would yield this answer.