Arena Etiquette--Rules of the Road--need picture

When sharing an arena with other riders, I am always confused about what to do when passing or being passed by another rider.  Here are the “rules of the road” if horses are traveling in opposite directions:

• If riding at the same gait (for example trotting), pass left shoulder to left shoulder.
• If riding at different speeds (for example one rider is at a walk and another at a trot), the faster rider passes on the inside.
• Don’t stop or back up if riding on the rail to avoid a “pile up.” 

From: Mullen, G.  (2008).  Amazing Horse Facts and Trivia.  Chartwell Books, Inc., New York. (p.111)