What does "improper loading" signify in the context of TDG?

Improper loading in the context of Transportation of Dangerous Goods (TDG) refers specifically to the failure to arrange dangerous goods correctly to ensure stability and to prevent any potential reactions between different substances. This is crucial because improper loading can lead to hazardous situations, such as spills, leaks, or even explosions if incompatible materials come into contact with each other.

Correct loading practices involve understanding the properties of the materials being transported, as well as adhering to regulations and guidelines that dictate how different dangerous goods must be arranged in a transport vehicle. The priority is to maintain safety during transportation, which can be jeopardized by incorrect stacking, securing, or positioning of these materials.

In this context, the other options do not fully capture the essence of what constitutes improper loading. Arranging cargo based on size and weight does not consider the chemical compatibility and stability of dangerous goods. Loading materials without documentation can be a serious issue, but it is not specifically about the arrangement of dangerous goods. Mixing non-dangerous goods with dangerous goods touches on a different aspect of transport regulations, focusing on safety and classification rather than the loading process itself. Thus, the emphasis on preventing instability or reactions is what makes the chosen answer accurate in defining improper loading.