When is it necessary for a spotter to fill out the TDR form?

The TDR form, or Trailer Data Report, is specifically required in circumstances where the Dock Lock is not engaged, which is referenced as DLINE. This is crucial because the Dock Lock's primary purpose is to secure the trailer during loading and unloading operations, ensuring that it does not move unintentionally. When the Dock Lock is not engaged, it creates a significant safety risk; therefore, filling out the TDR form serves to document this hazardous condition and allows for necessary mitigation steps to be taken.

Considering the nature of the other options, while dock operations and potentially hazardous situations are undeniably important in determining safety protocols, they do not explicitly require the TDR form to be completed unless a specific risk, such as the lack of engagement of the Dock Lock, is present. The presence of a trailer by itself does not mandate the form because trailers can be present for various reasons, not all of which involve safety risks that would need to be documented.