I agree with 3MX in that many (most) times the problem is our perception of an area or a totally irrational fear. (And, I would include racial, ethnic and age (any teen you see must be in a gang) in that.)
Adding to the problem is that if you've never lived in a "ghetto" you don't know what really goes on there and fearing the unknown is, unfortunately, a part of human nature.
I spent about 1 1/2 years in such an area in Akron about 22 years ago. From that, I learned first hand that if you mind your own business, you'll generally be OK. I also learned what to watch for that TRULY IS A BAD SIGN and to avoid that.
I don't go through those areas just to prove I'm tough. But, I don't shy away from them if I need to go there. Heightened awareness, yes, Nervousness, not so much.