The whole rulebook, plus the state you're in.

Search the official federal trucking rules from eCFR.gov by keyword or citation, or ask a question in plain words: safety rules, hours of service, hazmat, operating authority and leasing (49 CFR), federal size and weight (23 CFR 658) and the heavy vehicle use tax (26 CFR 41), checked for changes every day. Answers quote the federal rules and the state's own rules, with a link to every source.