The designation W in hazardous materials regulations relates to what type of transport?

The designation "W" in hazardous materials regulations specifically refers to transportation by water. This classification is part of the broader system for identifying the various modes of transport for hazardous materials, ensuring that the appropriate regulations and safety measures are applied based on the specific challenges and risks associated with each mode.

Transporting hazardous materials by water presents unique considerations, such as the potential for spills or leaks that could impact marine environments. Regulations related to this mode of transport are tailored to address the specific risks involved, such as securing the cargo against movement and ensuring proper labeling and containment.

In contrast, the other options involve different elements of transportation. Rail and air transport have their corresponding designations and regulations, while non-bulk packaging requirements relate to the size and type of container for shipping materials rather than the mode of transport. Therefore, understanding that "W" signifies water transport helps clarify the regulatory framework surrounding hazardous materials movement via this route.