To the best of my knowledge, reflective red and white DOT C2 tape or reflectors, known as conspicuity treatment, are not mandatory for single-unit box trucks. FMVSS 108 is a regulation for Tractor Trailer Rigs. Single-unit trucks or box trucks are not covered by this regulation. An effort began within the NHTSA in 2015 to add single-unit trucks (straight trucks) to the regulation via an update to FMVSS 108; however, it appears as though this effort was closed due to the inability of the NHTSA to show sufficient effectiveness to warrant the cost.
With this being said, reflective DOT C2 tape would certainly enhance the visibility of a straight box truck, and this improvement in visibility would likely reduce the chances of a collision. Since box trucks are often quite large, they pose many of the same dangers to other vehicles that full size semi trucks do. So marking them in the same manner makes sense.
Here is a full article on DOT Tape Requirements for Box or Straight Trucks. For more information, go to www.tapefinder.com and click on the contact link at the top of the page.
