{"data":{"id":"us/49-cfr-570.54","jurisdiction":"us","citation":"49 CFR 570.54","heading":"Definitions.","body":"Unless otherwise indicated, all terms used in this part that are defined in part 571 of this chapter, Motor Vehicle Safety Standards, are used as defined in that part.\nAir-over-hydraulic brake subsystem means a subsystem of the air brake that uses compressed air to transmit a force from the driver control to a hydraulic brake system to actuate the service brakes.\nElectric brake system means a system that uses electric current to actuate the service brake.\nVacuum brake system means a system that uses a vacuum and atmospheric pressure for transmitting a force from the driver control to the service brake, but does not include a system that uses vacuum only to assist the driver in applying muscular force to hydraulic or mechanical components.","path":["Title 49—Transportation","Subtitle B—Other Regulations Relating to Transportation","CHAPTER V—NATIONAL HIGHWAY TRAFFIC SAFETY ADMINISTRATION, DEPARTMENT OF TRANSPORTATION","PART 570—VEHICLE IN USE INSPECTION STANDARDS","Subpart B—Vehicles With GVWR of More Than 10,000 Pounds"],"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":"bcedcd4ca59c3a49f7b2565d3a4870dc29997868516e3f2a561802dfa965576a","source_id":"us-cfr","stale":true,"prev":"us/49-cfr-570.53","next":"us/49-cfr-570.55"},"notice":"GroundRules: Original legal text. Not legal advice."}