PDFWAC 296-52-68045
Open top vehicles.
(1) Locations of use. While loaded with explosives, open top vehicles must only be used on:
(a) The job site; or
(b) Roads that are closed to public travel.
(2) Containers. Explosives being transported in open top vehicles or trailers must be transported in:
(a) The original U.S. DOT approved shipping container or box; or
(b) A day box or portable magazine that complies with the requirements of this chapter.
(3) Securing containers. Explosive containers, boxes, day boxes, or portable magazines must be fastened to the bed of the vehicle or trailer.
(4) Loading. Packages of explosives cannot be loaded above the sides on open top vehicles.
(5) Tarpaulins (tarps).
(a) If an explosives transportation vehicle or trailer does not have a fully enclosed cargo area with nonsparking interior, the cargo bed and all explosive cargo must be covered with a flame and moisture proof tarp or other effective protection against moisture and sparks.
(b) Whenever tarps are used for covering explosives, both the tarp and the explosives container must be fastened to the body of the truck bed with rope, wire, or other equally efficient tie downs.