{"data":{"id":"us/49-cfr-236.1003","jurisdiction":"us","citation":"49 CFR 236.1003","heading":"Definitions.","body":"(a) Definitions contained in subparts G and H of this part apply equally to this subpart.\n(b) The following definitions apply to terms used only in this subpart unless otherwise stated:\nAfter-arrival mandatory directive means an authority to occupy a track which is issued to a train that is not effective and not to be acted upon until after the arrival and passing of a train, or trains, specifically identified in the authority.\nAssociate Administrator means the FRA Associate Administrator for Railroad Safety/Chief Safety Officer.\nClass I railroad means a railroad which in the last year for which revenues were reported exceeded the threshold established under regulations of the Surface Transportation Board (49 CFR part 1201.1-1 (2008)).\nCleartext means the un-encrypted text in its original, human readable, form. It is the input of an encryption or encipher process, and the output of an decryption or decipher process.\nControlling locomotive means Locomotive, controlling, as defined in § 232.5 of this chapter.\nCut out means any disabling of a PTC system, subsystem, or component en route (including when the PTC system cuts out on its own or a person cuts out the system with authorization), unless the cut out was necessary to exit PTC-governed territory and enter non-PTC territory.\nHost railroad means a railroad that has effective operating control over a segment of track.\nInitialization failure means any instance when a PTC system fails to activate on a locomotive or train, unless the PTC system successfully activates during a subsequent attempt in the same location or before entering PTC-governed territory. For the types of PTC systems that do not initialize by design, a failed departure test is considered an initialization failure for purposes of the reporting requirement under § 236.1029(h), unless the PTC system successfully passes the departure test during a subsequent attempt in the same location or before entering PTC-governed territory.\nInteroperability means the ability of a controlling locomotive to communicate with and respond to the PTC railroad's positive train control system, including uninterrupted movements over property boundaries.\nLimited operations means operations on main line track that have limited or no freight operations and are approved to be excluded from this subpart's PTC system implementation and operation requirements in accordance with § 236.1019(c);\nMain line means, except as provided in § 236.1019 or where all trains are limited to restricted speed within a yard or terminal area or on auxiliary or industry tracks, a segment or route of railroad tracks:\n(1) Of a Class I railroad, as documented in current timetables filed by the Class I railroad with the FRA under § 217.7 of this title, over which 5,000,000 or more gross tons of railroad traffic is transported annually; or\n(2) Used for regularly scheduled intercity or commuter rail passenger service, as defined in 49 U.S.C. 24102, or both. Tourist, scenic, historic, or excursion operations as defined in part 238 of this chapter are not considered intercity or commuter passenger service for purposes of this part.\nMain line track exclusion addendum (“MTEA”) means the document submitted under §§ 236.1011 and 236.1019 requesting to designate track as other than main line.\nMalfunction means any instance when a PTC system, subsystem, or component fails to perform the functions mandated under 49 U.S.C. 20157(i)(5), this subpart, or the applicable host railroad's PTCSP.\nMedium speed means, Speed, medium, as defined in subpart G of this part.\nNPI means a Notice of Product Intent (“NPI”) as further described in § 236.1013.\nPIH materials means materials poisonous by inhalation, as defined in §§ 171.8, 173.115, and 173.132 of this title.\nPTC means positive train control as further described in § 236.1005.\nPTCDP means a PTC Development Plan as further described in § 236.1013.\nPTCIP means a PTC Implementation Plan as required under 49 U.S.C. 20157 and further described in § 236.1011.\nPTCPVL means a PTC Product Vendor List as further described in § 236.1023.\nPTCSP means a PTC Safety Plan as further described in § 236.1015.\nPTC railroad means each Class I railroad and each entity providing regularly scheduled intercity or commuter rail passenger transportation required to implement or operate a PTC system.\nPTC System Certification means certification as required under 49 U.S.C. 20157 and further described in §§ 236.1009 and 236.1015.\nRequest for Amendment (“RFA”) means a request for an amendment of a plan or system made by a PTC railroad in accordance with § 236.1021.\nRequest for Expedited Certification (“REC”) means, as further described in § 236.1031, a request by a railroad to receive expedited consideration for PTC System Certification.\nRestricted speed means, Speed, restricted, as defined in subpart G of this part.\nSafe State means a system state that, when the system fails, cannot cause death, injury, occupational illness, or damage to or loss of equipment or property, or damage to the environment.\nSegment of track means any part of the railroad where a train operates.\nTemporal separation means that passenger and freight operations do not operate on any segment of shared track during the same period and as further defined under § 236.1019 and the process or processes in place to assure that result.\nTenant railroad means a railroad, other than a host railroad, operating on track upon which a PTC system is required.\nTrack segment means segment of track.\nType Approval means a number assigned to a particular PTC system indicating FRA agreement that the PTC system could fulfill the requirements of this subpart.\nTrain means one or more locomotives, coupled with or without cars.","path":["Title 49—Transportation","Subtitle B—Other Regulations Relating to Transportation","CHAPTER II—FEDERAL RAILROAD ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","PART 236—RULES, STANDARDS, AND INSTRUCTIONS GOVERNING THE INSTALLATION, INSPECTION, MAINTENANCE, AND REPAIR OF SIGNAL AND TRAIN CONTROL SYSTEMS, DEVICES, AND APPLIANCES","Subpart I—Positive Train Control Systems"],"source_url":"https://www.ecfr.gov/api/versioner/v1/full/2026-08-25/title-49.xml","current_through":"2026-08-25","vintage":"","retrieved_at":"2026-08-27T02:26:34Z","sha256":"d0bd7b7f2a480a3f4910e44328fd9ab3f75c46cfaff135e53b017102872c1f7d","source_id":"us-cfr","stale":true,"prev":"us/49-cfr-236.1001","next":"us/49-cfr-236.1005"},"notice":"GroundRules: Original legal text. Not legal advice."}