What distinguishes tube type top side rails from flat bar top rails?

The distinguishing factor between tube type top side rails and flat bar top rails is primarily the shape and design. Tube type top side rails are constructed in a cylindrical shape, which provides a different structural integrity and strength profile compared to the flat bar design, which is rectangular. This difference in shape influences several aspects of functionality, including rigidity, load distribution, and overall performance under stress. The design also affects how the rails interact with other components of the dry van structure, potentially impacting the vehicle's overall aerodynamics and weight distribution.

In contrast, while material type, thickness specification, and cost of production are all relevant considerations in rail construction, they do not inherently differentiate the two types of side rails as clearly as shape and design do. The fundamental geometry of the rails impacts their application and effectiveness, which is why this aspect is the key distinguishing feature.