Eye Contact with Random Passing Girls

Tweet

So I have this problem/curiosity. During my walks on my college campus, I often notice girls looking at me and we make eye contact, but they aren't smiling...it seems like more of a curious/unsure look. To not make them feel awkward or uncomfortable I break eye contact and look at the ground or something. I would actually like to meet some of these girls, but I'm not sure how to interpret their glances. It doesn't seem positive since they aren't smiling, but I dont know... So what does it mean when you girls look/make/hold eye contact with a random guy passerby without smiling? And is it offensive if the guy breaks eye contact like I do?