Depends on the bell and where you are. Here in Seattle most people seem to understand the bell, assuming they can hear it. Do everyone a favor a buy a large brass bell. Brass bells are in a league their own. The Crane Suzu is amazing. I was totally happy with my quite decent "Temple of Tone" bells for many, many years, but when I got my girlfriend a nice Crane Suzu and I heard it for the first time, I knew that my favorite bell for nearly two decades was obsolete. The tone is super clear and carries about twice as far as any other bell I've heard. When we ride together, I ask her to use her bell even if she's behind me, because it carries so much further and is clearer and louder. Despite having a stockpile of Temple of Tones, I bought a Crane for the new commuter I'm building up. Absurdly, it's one of the things I'm most looking forward to when that build is complete. Love me a good bell!

The more time people have to react, the less problems you will have. A bell with longer reach will give you that time.