There are no EPA requirements to use dedicated tank trucks to transport ULSD. It is the responsibility of the tank truck operator to ensure that whatever contamination that might take place while the ULSD is in the operator's custody does not cause the 15 ppm cap on sulfur content to be exceeded.
Additional quality control measures may be needed to limit sulfur contamination if an operator chooses to use a tank truck compartment to alternately transport ULSD and high sulfur products.
Question and Answer was originally posted at Questions and Answers on the Clean Diesel Fuel Rules (PDF)(135 pp, 888 K, EPA420-B-06-010, July 2006, About PDF)