page_title: Electro-pneumatic brake system on British railway trains
section_title: The Next Generation
hierarchical_section_title: Electro-pneumatic brake system on British railway trains / The Next Generation
caption_attribution_description: English: UK Electric Multiple Unit Brake Handle, showing five positions; Release, Step 1, Step 2, Full service brake and Emergency brake
context_page_description: The Electro-pneumatic brake system on British railway trains was introduced in 1950 and remains the primary braking system for multiple units in service today. The Southern Region of British Railways operated a self-contained fleet of electric multiple units for suburban and middle distance passenger trains. From 1950, an expansion of the fleet was undertaken and the new build adopted a braking system that was novel in the UK, the electro-pneumatic brake in which compressed air brake operation was controlled electrically by the driver. This was a considerable and successful technical advance, enabling a quicker and more sensitive response to the driver's operation of brake controls.
context_section_description: Following on from the original EP stock, the system was developed further on the second generation of Multiple Unit trains built for British Rail in the 1970s such as the Class 313 EMU.
  The Westinghouse air system was abandoned in favour of a fully electrical system of control, so that the need for a brake pipe and triple-valves was dispensed with. Instead a single air pipe, now called the Main Reservoir Pipe runs the length of the train. It operates at 10 bar and in addition to feeding each brake cylinder reservoir also provides air for the secondary suspension systems (air bags) and power doors. 
  Each brake reservoir stores air at a pressure of 7 bar and is fed via a pressure reducing valve off the Main Reservoir Pipe. The driver's brake handle passes control voltages down three wires to each EP control valve, which allows air from the brake reservoir to pass into the brake cylinder, thereby activating the disc brake. The presence of the voltage holds the brakes off, providing a Fail Safe system. 
  The 3 step "Westcode" brake uses three wires and these operate in a binary sequence to control the brake step. 10 & 11 are the brake coding to provide the 3 steps, 12 wire is emergency brake, 15 wire is EP brake negative.
  Positions on the brake handle are:
  Release - Trainwires 10,11 and 12 energised
  Step 1 - Trainwire 10 de-energised, 11 energised, 12 energised
  Step 2 - Trainwire 10 energised, 11 de-energised, 12 energised
  Step 3 - Trainwire 10 de-energised, 11 de-energised, 12 energised.
  Emergency - All three Trainwires de-energised and earthed
  This system remains in use today.
caption: Driver's brake handle on a Class 317 Electric Multiple Unit
exif: {"Image Make": "FUJIFILM", "Image Model": "FinePix A500", "Image Orientation": "Horizontal (normal)", "Image XResolution": "72", "Image YResolution": "72", "Image ResolutionUnit": "Pixels/Inch", "Image Software": "Adobe Photoshop CS Windows", "Image DateTime": "2009:09:25 13:42:08", "Image YCbCrPositioning": "Co-sited", "Image Copyright": "", "Image PrintIM": "[80, 114, 105, 110, 116, 73, 77, 0, 48, 50, 53, 48, 0, 0, 0, 2, 0, 2, 1, 0, 0, 0, 1, 1, 0, 0, 0, 0]", "Image ExifOffset": "280", "Thumbnail Compression": "JPEG (old-style)", "Thumbnail XResolution": "72", "Thumbnail YResolution": "72", "Thumbnail ResolutionUnit": "Pixels/Inch", "Thumbnail JPEGInterchangeFormat": "962", "Thumbnail JPEGInterchangeFormatLength": "4637", "EXIF ExposureTime": "1/30", "EXIF FNumber": "17/2", "EXIF ExposureProgram": "Program Normal", "EXIF ISOSpeedRatings": "100", "EXIF ExifVersion": "0220", "EXIF DateTimeOriginal": "2001:04:04 08:38:00", "EXIF DateTimeDigitized": "2001:04:04 08:38:00", "EXIF ComponentsConfiguration": "YCbCr", "EXIF CompressedBitsPerPixel": "4", "EXIF ShutterSpeedValue": "5", "EXIF ApertureValue": "31/5", "EXIF BrightnessValue": "301/100", "EXIF ExposureBiasValue": "0", "EXIF MaxApertureValue": "17/5", "EXIF MeteringMode": "Pattern", "EXIF LightSource": "Unknown", "EXIF Flash": "Flash fired, compulsory flash mode", "EXIF FocalLength": "32/5", "EXIF FlashPixVersion": "0100", "EXIF ColorSpace": "sRGB", "EXIF ExifImageWidth": "800", "EXIF ExifImageLength": "622", "Interoperability InteroperabilityIndex": "R98", "Interoperability InteroperabilityVersion": "[48, 49, 48, 48]", "EXIF InteroperabilityOffset": "836", "EXIF FocalPlaneXResolution": "4442", "EXIF FocalPlaneYResolution": "4442", "EXIF FocalPlaneResolutionUnit": "3", "EXIF SensingMethod": "One-chip color area", "EXIF FileSource": "Digital Camera", "EXIF SceneType": "Directly Photographed", "EXIF CustomRendered": "Normal", "EXIF ExposureMode": "Auto Exposure", "EXIF WhiteBalance": "Auto", "EXIF SceneCaptureType": "Standard", "EXIF Sharpness": "Normal", "EXIF SubjectDistanceRange": "0"}