Differences

This shows you the differences between two versions of the page.

Link to this comparison view

Both sides previous revision Previous revision
Next revision
Previous revision
notes:bart [2016/08/28 07:36]
Jesse B. Crawford
notes:bart [2019/06/18 02:57] (current)
Line 15: Line 15:
 There is a released [[http://​www.itscalifornia.org/​Content/​Meetings/​NorCal/​2015/​20150619-BART-TrainControlModernization.pdf|presentation on control modernization]]. There is also information in an old [[https://​archive.org/​details/​ECL-224|Univ. Santa Clara engineering case study]]. Also see an [[https://​www.transit.dot.gov/​sites/​fta.dot.gov/​files/​FTA_Report_No._0035.pdf|FTA report]] which is very long but has a case study on BART. There is a released [[http://​www.itscalifornia.org/​Content/​Meetings/​NorCal/​2015/​20150619-BART-TrainControlModernization.pdf|presentation on control modernization]]. There is also information in an old [[https://​archive.org/​details/​ECL-224|Univ. Santa Clara engineering case study]]. Also see an [[https://​www.transit.dot.gov/​sites/​fta.dot.gov/​files/​FTA_Report_No._0035.pdf|FTA report]] which is very long but has a case study on BART.
  
-BART is primarily controlled by the Integrated Control System (ICS), based on track circuit communication. ACS is a speed-authority system in which each train is authorized to a specific speed value of 80, 70, 50, 36, 27, 18, 6, or 0 mph. Obviously, the commanded speed in the block before an occupied block must be 0 to avoid collision. Elsewhere, the speed is limited by either a design speed limit or the distance to the next occupied block. The BART track circuits run at an abnormally low voltage, which leads to issues when there is any corrosion on tracks. The track circuit is modulated at audio frequencies for control signals. Safety is based on simple block occupancy of variable-length blocks as short as 70 feet.+BART is primarily controlled by the Integrated Control System (ICS), based on track circuit communication. ACS is a speed-authority system in which each train is authorized to a specific speed value of 80, 70, 50, 36, 27, 18, 6, or 0 mph. Obviously, the commanded speed in the block before an occupied block must be 0 to avoid collision. Elsewhere, the speed is limited by either a design speed limit or the distance to the next occupied block. Blocks are as short as 70 feet, but generally must be long enough to allow a train to stop within their length. The BART track circuits run at an abnormally low voltage, which leads to issues when there is any corrosion on tracks. The track circuit is modulated at audio frequencies for control signals, exact range unclear.
  
 There is also a "​backup"​ train protection system called SORS, or Sequential Occupancy Release System. It works by detecting when the lead car has entered a block, and then releasing that block when the lead car is detected in another block that is a distance greater than the length of the train farther ahead. This means that missed detections result in a block behind the train remaining in the occupied state, a '​fail-safe'​ condition that is cleared by the control center when necessary. SORS is '​non-vital'​ as a safety system. There is also a "​backup"​ train protection system called SORS, or Sequential Occupancy Release System. It works by detecting when the lead car has entered a block, and then releasing that block when the lead car is detected in another block that is a distance greater than the length of the train farther ahead. This means that missed detections result in a block behind the train remaining in the occupied state, a '​fail-safe'​ condition that is cleared by the control center when necessary. SORS is '​non-vital'​ as a safety system.
  
 The Advanced Automatic Train Control system was [[http://​ntl.bts.gov/​lib/​6000/​6600/​6646/​attc.html|contracted by BART]] with Hughes Aircraft in 1998 to replace the BART train control system. This [[http://​www.bart.gov/​news/​articles/​2006/​news20060616a|did not end well]]. As of 2003, this project was [[http://​www.tsd.org/​papers/​SFBART-CBTCMay%202003.ppt|still in progress]] with some test trains equipped and a section of track set up with wayside equipment. However, this project seems to be a total failure and has never gone into revenue service. Had the project gone anywhere, it would have implemented a "​moving block" system based on radio sensing of the exact position of each train. The Advanced Automatic Train Control system was [[http://​ntl.bts.gov/​lib/​6000/​6600/​6646/​attc.html|contracted by BART]] with Hughes Aircraft in 1998 to replace the BART train control system. This [[http://​www.bart.gov/​news/​articles/​2006/​news20060616a|did not end well]]. As of 2003, this project was [[http://​www.tsd.org/​papers/​SFBART-CBTCMay%202003.ppt|still in progress]] with some test trains equipped and a section of track set up with wayside equipment. However, this project seems to be a total failure and has never gone into revenue service. Had the project gone anywhere, it would have implemented a "​moving block" system based on radio sensing of the exact position of each train.