I'm not trolling you when I say you might consider studying these subjects in college. I saw another comment that you're a teenager. You clearly have a lot of interest in this sort of thing, but I hate to tell you the notions you're proposing are so unrealistic as to essentially be science fiction. A pedestrian tunnel is extraordinarily implausible and is not something that would ever happen. Study these things for a few years though and you might come up with some genuine ideas, but I think you'll find your old posts here a bit embarrassing. (All adults are embarrassed by their teenage antics, so don't worry about that.)