There are lots of great reasons to outfit your bike with a bell, but here’s one you may not expect.
According to Massachusetts General Law Ch. 85 § 11B, whenever you’re riding on the sidewalk, you must “give an audible signal before overtaking and passing any pedestrian.”
As I’ve discussed before, if you injure someone while you’re breaking a law that’s meant to protect them, you’re at fault. In this case, that means that even if the pedestrian makes a sudden, unexpected movement into your path, you’ll be on the hook for his medical bills if you didn’t ring your bell before passing.
Let me be clear: I don’t like this law. I’d much prefer if we had something like the system described in this article about bell use in Germany. It makes much more sense to save audible signaling for when it’s absolutely necessary.
However, these are the laws we’ve got, and bicycle bells cost less than medical bills. So get yourself one—it’s the cheapest insurance policy around.