I've lived in Oakland for ~8 months and I'm yet to be in a situation where I felt at risk (disclaimer: I'm a reasonably tall man and rarely feel at risk in cities). I live north of Lake Merrit, work in Jack London Square, and deliver bagels up and down Broadway and Telegraph on my bike. Primarily traversing that terrain, I feel very safe.

That said, there are other parts of the city that are much more dangerous. I generally put these in two categories: (1) neighborhoods with a high concentration of crimes like robberies and (2) neighborhoods where gang-related violence occurs. (2) is very often a subset of (1).

I'm not an expert, but from my understanding, (2) areas are heavily concentrated in East Oakland (east of Park Blvd), so if you generally don't traverse that part of the city, you avoid much of that danger.