I occasionally commute through a such-regarded section of Boston, so it's not mandatory for me, but by choice as a route variation. I ride the main streets, and while traffic is more, there is more traffic, i.e. less secluded. More secure though for me is that I ride in the early morning. IMO in any environment, the most responsible and reliable people are out on the streets between the hours of 4 to 6 AM. By 4 AM, the bars have been closed for two hours, and the crazies have likely reached their destination. After 6:00, the commuter lemmings are out. I think of my fellow travelers during those golden hours as the people entrusted with getting the world started up for the day.