Before any rule in this book applies to you, one question has to be answered: does the federal rulebook reach what you are doing at all? § 390.3T draws the main line. The safety regulations apply to all employers, employees, and commercial motor vehicles that transport property or passengers in interstate commerce — and that phrase is narrower and stranger than it sounds. Under § 390.5T, interstate commerce means trade, traffic, or transportation between a place in a State and a place outside it; between two places in a State but passing through another State or outside the country; or between two places in the same State as part of transportation that originates or terminates outside the State. That third branch is the one that catches people out. Freight whose wheels never leave your state can still be moving in interstate commerce if the leg you are driving is part of a longer journey that began or will end somewhere else. The question the rule asks is not where you drive; it is where the freight is going. One note on the citations in this chapter: Part 390’s § 390.3 and § 390.5 are suspended, and the T-suffixed sections § 390.3T and § 390.5T are the ones in force, which is why this book cites the T forms throughout.

Then comes an asymmetry worth carrying through the whole book. § 390.3T(b) applies Part 383 — the commercial driver’s license rules — to every person who operates a commercial motor vehicle as § 383.5 defines it, in interstate or intrastate commerce, and to all employers of such persons. § 383.3(a) says the same thing from the other direction, reaching every person who operates such a vehicle in interstate, foreign, or intrastate commerce. So the license rules follow you inside a single State even where the wider body of safety regulation does not. A driver who never crosses a State line may still need a commercial driver’s license, and everything Part 383 sets out — the classes, the endorsements, the testing, the disqualifications — still governs them. Hold that shape rather than the detail: the license question and the safety-regulation question have different answers, and Chapter 2 takes applicability apart properly, exceptions included.

Two more definitions decide who the rules are talking to, and both are broader than a job title. A driver, under § 390.5T, is any person who operates any commercial motor vehicle — the term describes the act, so it reaches an owner-operator and an occasional driver as surely as a full-time employee. An employer is any person engaged in a business affecting interstate commerce who owns or leases a commercial motor vehicle in connection with that business, or assigns employees to operate it. The pairing matters because § 390.3T(e) puts a duty on each: every employer must be knowledgeable of and comply with the regulations applicable to its operations, and every driver and employee must be instructed regarding, and comply with, the applicable regulations. Nobody in that chain gets to treat the rulebook as somebody else’s responsibility.