I'll admit I was never a speed demon with my walker, it was set up more as a Touring/Utility walker. As far as passing most pedestrians, or as I got to calling them "Simple Bipeds" they'll blow past you before you can react to them anyway, so it's best to just let them do their thing. As I mentioned in the other thread, the ones you have to look out for are the high speed old ladies... the ones with the tricked out walkers with wheels on the front, and tennis balls on the back legs...

True story; about a week after my hip replacement I had to go to the Lab for some blood work. It was the first time I had really been out in public on my walker, and I was under no touch down weight rules for my left leg; so I was taking it slow and careful. I was about half way to where I needed to be, when all at once I hear "Get out of the way" and a little ole gray headed woman literally pushing her walker like a construction worker would push a wheel-barrel in a race, damned near knocked me over as she blew past. So, I don't know if "On your left" works very well, But, "Get out of the way" is not a good thing to say. I would have told that old woman too, if I could ever have caught up to her. The mood I was in, and the drugs I was on, she is lucky I didn't throw my water bottle at her. Lucky for the old woman, my wife was parking the car at the time, and missed the whole event.