CFR›Title 49›Subtitle B›Chapter II›Part 236›Subpart B ContainsSubject group StandardsCorpusDaily eCFRDisplayed edition2026-04-27Last updated2026-04-27 Subpart B—Automatic Block Signal Systems Subject Groups Standards Standards Sections 236.201–236.207 Previous Appendix F to Part 236 Appendix F to Part 236—Minimum Requirements of FRA Directed Independent Third-Party Assessment of PTC System Safety Verification and Validation Next C Subpart C—Interlocking