Final answer:
Trench or conduit covers in plant roadways are indeed required to support a significant load, typically at least 20,000 lbs, to ensure safety and functionality for heavy industrial traffic.
Step-by-step explanation:
The question pertains to the design requirements for trench or conduit covers and their supports when they are situated in plant roadways. It states that these structures must be capable of supporting at least a 20,000 lbs rear-axle load of a truck. This is generally true, as engineering standards and building codes often specify that infrastructure in industrial or commercial settings, such as plant roadways, must be able to withstand heavy loads. The design load takes into account the types of vehicles that are expected to pass over these covers, which in an industrial setting could include heavy trucks. Therefore, ensuring the structural integrity to support at least a 20,000 lbs load is crucial for safety and functionality.