What The Bell Signals Mean On The San Francisco Cable Cars

I have been riding the SF cable cars almost every day for >20 yrs. Tonight I explained to some tourists what the different bell signals mean and thought I'd create a list. Context-two people work on cable car. On the front is the gripman or "grip". On the back is the conductor who works the back brake and collects fares when safe. Instagram @lmc_sf
  1. 1.
    One Bell means stop at the next stop or, if already stopped, it means don't leave the stop yet, someone is getting on or off.
  2. 2.
    Two Bells means ok to go. Generally this is while at a stop- the conductor will ring the bell twice to tell the grip it's OK to go. Sometimes the grip will ring the bell twice as if to ask the question "is it OK to go?", and the conductor will respond with two bells.
  3. 3.
    Three Bells means stop immediately. Stopping immediately is difficult to do and dangerous. The only time I remember three bells is when some drunk almost fell off while joking around with his friends.
  4. 4.
    Four Bells means back up. Cars rarely back up on route. If they do it is to roll down the hill backwards and start up again when they have been blocked. When cars return to the cable car barn at end of shift they pull slightly past the entrance and then back in (this is right below my apt & I hear them yell "four bells" instead of ringing the bell.