When is it mandatory to have a spotter during TDR?

The correct answer highlights the need for a spotter when TDR (Tow, Drive, and Retrieve) is being performed outside. This requirement is rooted in safety protocols designed to ensure the well-being of personnel as well as to mitigate potential hazards present in outdoor environments. When TDR occurs outdoors, factors such as uneven surfaces and obstacles can pose significant risks. A spotter serves as an additional layer of safety by monitoring the surroundings and providing guidance to the driver, helping to prevent accidents or injuries during operations.

In contrast, the other scenarios presented do not consistently demonstrate the same level of necessity for a spotter. For instance, while dealing with hazardous materials is inherently risky, the presence of a spotter might be dictated by specific protocols related to those materials rather than a blanket rule applicable to all situations. The dynamic of having a spotter based on a driver's request may not always guarantee safety, as it is not a standardized requirement and could ignore specific environmental conditions that demand vigilance. Moreover, stating that a spotter is required at all times during TDR would not take into consideration contexts where the risk may be minimal, such as controlled environments. Thus, the focus on outdoor operations emphasizes the heightened safety protocols necessary in variable and potentially uncontrolled environments.