US lawFederal (United States)RegulationsTitle 49 CFR — TransportationChapter II — FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATIONPart 236 — RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCESSubpart G — Definitions236.70949 C.F.R. § 236.709Block, absolute.Last amended: 2017Year: 2026Length: 17 wordsOfficial source Cite as 49 C.F.R. § 236.709 (2026)A block in which no train is permitted to enter while it is occupied by another train.Previous49 C.F.R. § 236.708Next49 C.F.R. § 236.710