If you must back a trailer along a curved path rather than a straight line, which side should you back toward, and why?

AAMVA CDL Manual, Section 6.1.7 "Backing with a Trailer," p. 6-3-6-4, Figure 6.5

Backing blind on the passenger's side of a curved path leaves a driver relying entirely on mirrors for a maneuver that is already difficult to judge. Choosing the driver's-side curve whenever there is a choice gives a direct, unobstructed view of the trailer's path.