When backing a commercial motor vehicle, why is backing toward the driver's side the preferred choice whenever it is possible?

Explanation

Whenever it is possible, the preferred practice when backing a commercial motor vehicle is to turn toward the driver's side, because that position lets the driver watch the rear of the vehicle directly through the side window, rather than relying only on mirrors. Backing maneuvers are part of the required knowledge CDL applicants must have under 49 CFR 383.111(a)(6)(i), but that paragraph only names backing principles as a required knowledge topic; it does not itself specify which side to turn toward, so this driver's-side preference is standard driver-training guidance rather than a codified federal rule. A backup alarm's placement and the vehicle's exhaust routing are both fixed features of the vehicle, unrelated to which way the driver chooses to turn while backing. Transmission wear also has nothing to do with which side a driver backs toward, since the mechanical operation of reverse gear is identical either way.

Source: 49 CFR 383.111(a)(6)(i)