49 CFR § 177.804 - Compliance with Federal Motor Carrier Safety Regulations.
(a)General.Motor carriers and other persons subject to this part must comply with 49 CFR part 383 and 49 CFR parts 390 through 397 (excluding §§ 397.3 and 397.9) to the extent those regulations apply.
(b)Additional prohibitions. A person transporting a quantity of hazardous materials requiring placarding under 49 CFR part 172 or any quantity of a material listed as a select agent or toxin in 42 CFR part 73:
(1) Must comply with the safe clearance requirements for highway-rail grade crossings in § 392.12 of this title;
(2) May not engage in, allow, or require texting while driving, in accordance with § 392.80 of this title; and
(3) May not engage in, allow, or require the use of a hand-held mobile telephone while driving, in accordance with § 392.82 of this title.