Originally Posted by
Koyote
I would have thought it to be obvious, but will spell it out for you: I would have both hands on the bar, trying to avoid the motor vehicle.
My bells and horns are attached so the tabs and push buttons are right under my thumb when I'm holding the handlebar with both hands. I can dodge and avoid motor vehicles AND sound my horn at the same time. Better still, look ahead and anticipate dangers.
Look at the photo Sweeks posted, just above.
Sound your horn at motor vehicles to avoid any incidences. On trails, ring your bell first. Again, if you don't get a reaction, try again and then revert to something else that's louder.