rule of the road
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rule of the road
n. often pl. rules of the road
1. A set of customary practices, especially for the operation of a motor vehicle, boat, or aircraft, established to promote efficiency and safety.
2. A set of established rules or practices, usually unstated, intended to minimize confusion or conflict: "Great powers ... wishing to avoid war could resort to one of three tools: condominium, spheres of influence or rules of the road" (Charles William Maynes).
American Heritage® Dictionary of the English Language, Fifth Edition. Copyright © 2016 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.