Besides changing lanes, in which of these situations should a driver check mirrors more often than usual?

Explanation

Turns, merges, and any tight maneuvering in close quarters all call for more frequent mirror checks than ordinary driving, since each situation puts part of the vehicle at risk of contacting something the driver cannot see without checking, whether that is the rear of the vehicle swinging into an obstacle on a turn or another vehicle occupying the gap needed for a merge. Use of mirrors and seeing to the rear are part of the required knowledge CDL applicants must have under 49 CFR 383.111(a)(7)(ii) and (iii), but those paragraphs only name these as required knowledge topics; they do not themselves list these specific situations, which is standard driver-training guidance rather than a codified federal rule. Highway speed, time of day, and whether the vehicle is loaded are all unrelated to when extra mirror checks are needed.

Source: 49 CFR 383.111(a)(7)(ii) and (iii)