keep on the left side
keep on the left(-hand) side
To remain on the left-most side (of something, especially a road or path). Turn right and walk toward the Main Street Bank, keeping on the left-hand side of the road as you go, and you'll be sure to see our shop. I always have to remind myself to keep on the left side of the road when I drive in the UK.
Farlex Dictionary of Idioms. © 2015 Farlex, Inc, all rights reserved.
keep on the left(-hand) side (of something)
to stay on the left-hand side of something. Please don't keep on the left side all the time when everyone else is on the right! In England you keep on the left-hand side.
McGraw-Hill Dictionary of American Idioms and Phrasal Verbs. © 2002 by The McGraw-Hill Companies, Inc.