Regulations issued by FMCSA are published in the Federal Register and compiled in the U.S. Code of Federal Regulations (CFR)

49 CFR Parts 300-399 FMCSA Regulations

https://www.fmcsa.dot.gov/regulations/title49/b/5/3

49 CFR Part 40 - Procedures for Transportation Workplace Drug and Alcohol Testing Programs

https://www.ecfr.gov/current/title-49/subtitle-A/part-40?

49 CFR Parts 100-180 - Hazardous Materials Regulations

toc=1http://www.ecfr.gov/current/title-49/subtitle-B/chapter-I

49 CFR Part 571 - Federal Motor Vehicle Safety Standards

https://www.ecfr.gov/current/title-49/subtitle-B/chapter-V/part-571