Consider a standard hold over a fix at 10,000 feet. A pilot might think, "I’ll just fly a 1-minute leg." But according to Doc 8168 Volume 3, if the temperature is -30°C, the true airspeed (TAS) increases, thus the aircraft covers more ground distance. The designer must expand the protected area accordingly. Failure to do so results in the aircraft flying into a mountain 5 miles away that was "outside" the standard template.
Before GPS and RNAV, reversal procedures were the only way to turn an aircraft 180 degrees after passing a fix to intercept an inbound track. Volume 3 codifies two types: icao doc 8168 volume 3
Critical insight from Volume 3: The document explicitly states that a "procedure turn" is not a random maneuver. It mandates that the outbound track must be offset from the inbound track to prevent the aircraft from turning into its own wake or terrain. It also provides the obstacle clearance templates (the "racetrack" shape on a chart). Consider a standard hold over a fix at 10,000 feet
Given weather, temperature, altitude, helicopter performance class (1, 2, or 3): Critical insight from Volume 3: The document explicitly
It serves as the international standard. If a country wants to approve an airline for CAT III landings, they use Volume III as the template to ensure they haven't missed a safety step.