I apologize for not intentionally startling you, cranky lady

Having spent the last several months going on not too infrequent bike rides, I've developed the ability to predict whether it's necessary to alert someone walking in front of me that I'm going to be passing on their left. It is definitely common courtesy, but in my experience, mostly unnecessary.

If you're walking ahead of me, I'm going to have plenty of time to observe your walking "style" and decide whether you might need a little heads up that I'm going to ride by. If you're doing a great job of walking in a straight line and staying on the right-side of the path (super proud of you, btw), I typically decide that I can trust you not wander into oncoming traffic without looking first. I have found that I am more likely to startle you by ringing my bell than by riding past you, and that unpleasantness usually seems wholly unnecessary. However, if you're a wanderer or part of a larger group of walkers, I'm definitely ringing my bell, even though I'll feel a little bad when you jump in surprise. Safety first!

So far, this method has worked well for me, and no one that I've decided to "trust" has let me down. During our bike ride today, a lady was walking her dog ahead of us (puppers was on her right), and I observed them for awhile before I was close enough to pass. She was doing great. So was her dog. I thought, "I can trust her. She's aware of her surroundings", and opted not to ring my bell (I did that for you, Janet). Also, Dan and I were talking (somewhat loudly) as we were nearing her and I figured she was likely to have heard us.

We passed her with no incident.

"Thanks for the heads up!", she snarled after us.

"Sorry about that, hope you're ok!", I called back. 

Yes, I was snarky. My internet persona is The Snarky Humanist after all, and while I try to limit the amount of snark directed at single person (rather than a group or situation), she caught me by surprise by being that mad that nothing bad happened as a result of us not giving her a heads up.

Dan, very amused by my response suggested that I make sure to give her a heads up when we passed her again on our way back (which was very likely). I assured him that I would alert the fuck out of her since she basically admitted that she can't be trusted not to run out into traffic without looking. Alas, cranky lady and her not-cranky dog were not spotted again, and I continued my usual method of alerting people when I was ready to pass only when I deemed necessary.

I do hope cranky lady recovered from this incident, and would suggest to her that if she wants to guarantee that bikers will alert her moving forward, maybe drink a six pack before starting her walk to ensure she's walking as erratically as possible.