Aim mirrors so the horizon is closer to the top edge for better coverage of blind spots close to the sides of the truck.
TMC recommends mounting mirrors so the inner edges are at least 1 inch outboard of the widest portion of the load or cargo box (left). If they are closer than 1 inch, there will be blind spots (right).

Mirror placement and aim are also critical to proper sight lines. An informal survey done a few years ago by the Technology and Maintenance Council (TMC) found that a significant number of trucks had positioned their mirrors too far inboard. Drivers' vision was blocked by the front of the body, rather than allowing vision beyond the rear.

TMC Recommended Practice RP 425, “Mirror Positioning and Aiming Guidelines,” recommends mounting mirrors so “the inner edge of the mirror is at least 1 inch outboard of the widest portion of the load or cargo box on the truck or trailer (Click here to see diagram). The preferable position is for the mirror to be as far outboard as is practical, considering causes of physical damage to the mirror.”

TMC also found most drivers aim outside mirrors so the horizon is halfway up the mirror, matching normal sightlines. This position wastes much of the mirror's area because it includes too much sky in the field of view. When drivers aim the mirrors so the horizon is within 1 to 1½ inches (depending on mirror height) of the mirror's top edge, they get a better coverage of blind spots close to the sides of the truck.

Electronic aids

No matter how good a mirror may be, its field of view will always be blocked by the drum or some portion of the load. For the ultimate in rearview vision, especially when backing, nothing is better than television. Several companies make them. Many are as useful at night down to O.5 lux (about one-half candlepower) as they are in broad daylight.

Using advanced technology, cameras can differentiate subtle differences in shading and eliminate light bloom, the annoying halo effect caused on TV screens by bright lights that can mask important details. Be sure to place the monitor where glare will not affect comprehension.

Infrared thermal cameras are new to civilian markets. Adapted from military technology, they sense heat four or more times farther than headlights can illuminate. People invisible to our eyes will show up on compact viewing screens. They're designed to be used like mirrors, given a quick glance a few times a minute. Object definition is quite good and glare from oncoming headlights is virtually eliminated in the viewing screen.

Electronic ranging and blind spot detection have proven their worth in fleet use over the past decade. One operator reported a significant reduction in crashes caused by following too closely with a radar-based range warning. Radar-based proximity warnings also help with backing up and lane changing. While these devices are initially expensive, they are more than offset with lower insurance premiums due to fewer and smaller claims and a decrease in accidents.

— Paul Abelson if a former director of the Technology and Maintenance Council of the American Trucking Association.