Editing SkyTrain (Vancouver) (section)

=== Technology ===
The [[railway signalling|signalling technology]] used on all three SkyTrain lines to run trains automatically was originally developed by [[Alcatel-Lucent|Alcatel]] and loaded from a [[Floppy disk|3.5" diskette]]. There were initially four systems called the vehicle control computer (VCC) with three divided over the mainline and one for the storage yard. VCC1 controls trains from Waterfront to Royal Oak; VCC2 controls trains from Royal Oak to King George (it now also controls a portion of the Millennium Line); and VCC3 controls trains in the yard. Additional VCCs were added as Skytrain expanded. Each VCC is a cluster of three IBM Type 7588 rack-mount single-board computers with Intel-IA32 Pentium processors and proprietary hardware in a fault-tolerant configuration.<ref>{{Cite web|url=https://vancouversun.com/news/metro/inside-the-skytrain-control-room |title=Inside the SkyTrain control room |work=Vancouver Sun |date=August 4, 2014 |access-date=December 27, 2024 |first=Kelly |last=Sinoski |archive-url=https://web.archive.org/web/20241227193153/https://vancouversun.com/news/metro/inside-the-skytrain-control-room |archive-date=December 27, 2024}}</ref> For example, VCC3 is composed of CPU1, CPU2, and CPU3. For every command that is sent to a train, at least two of the CPUs must agree with the action, otherwise an error is generated and the command is ignored. The VCC communicates with the train's vehicle on board computer (VOBC), whose data is transmitted through coax cables laid along the tracks. There are up to two VOBCs per married-pair trains, i.e. 4-car train would have two VOBCs. If the VCCs fail or communication between the VCC and the VOBC is lost, the train will "time-out" and emergency-brake (EB) through a [[Quester Tangent Corporation|Quester Tangent]] brake assurance monitor (BAM) that controls propulsion and braking systems.<ref name="HMU" /> The VCCs have a command-line-console, but normally the trains are controlled through a system known as the SMC, which also provides scheduling. All commands from the SMC are verified to be safe by the VCC before execution. However if the SMC fails, the system can still be operated through the VCC. This is known as "degraded mode". The SkyTrain health monitoring unit (HMU) developed by [[Quester Tangent Corporation|Quester Tangent]]<ref name="HMU">{{Cite web |url=http://www.questertangent.com/our-projects/?pid=448 |title=Quester Tangent – SkyTrain for Fleet Operators |access-date=March 25, 2015 |archive-url=https://web.archive.org/web/20150306193310/http://www.questertangent.com/our-projects/?pid=448 |archive-date=March 6, 2015 |url-status=live}}</ref> provides monitoring and diagnostic functionality for vehicle maintenance by connecting to CAN vehicle network and providing a maintenance display in the Hostler Panel.<ref name="HMU" />

SkyTrain's signalling system later provided the basis of [[SelTrac]], which is currently maintained and sold by [[Thales Rail Signalling Solutions|Thales]] and has equipped many lines around the world. Largely as a result of this, the Expo and Millennium Lines have a combined punctuality record of over 96 percent; the principal cause of train delays is passenger interference with train doors.<ref>{{cite web |title=A Timely SkyTrain Safety Reminder / A near-miss: a timely reminder – wait for the next train! |url=http://www.translink.ca/en/About-TransLink/Media/2009/July/A-Timely-SkyTrain-Safety-Reminder.aspx |publisher=TransLink |date=July 17, 2009 |quote=In 2007 and 2008, 981 delays were caused by vehicle issues: 55% of those involved the doors, many of them held open by passengers.... With over 96% on-time performance, SkyTrain is rapid, ready and reliable. |access-date=August 11, 2009 |archive-url=https://web.archive.org/web/20090819135028/http://www.translink.ca/en/About-TransLink/Media/2009/July/A-Timely-SkyTrain-Safety-Reminder.aspx |archive-date=August 19, 2009}}</ref> There have been two derailments during revenue service in the system's history.<ref>{{cite news |title=TransLink investigates train derailment |url=https://vancouversun.com/TransLink+investigates+SkyTrain+derailment/3084244/story.html |work=Vancouver Sun |access-date=May 28, 2010 |archive-url=https://web.archive.org/web/20100531193010/http://www.vancouversun.com/TransLink+investigates+SkyTrain+derailment/3084244/story.html |archive-date=May 31, 2010}}</ref><ref>{{Cite web |title=Two sheared bolts caused SkyTrain derailment: FOI documents |url=https://biv.com/article/2022/09/two-sheared-bolts-caused-skytrain-derailment-foi-documents |access-date=2023-08-23 |website=Business in Vancouver |date=September 28, 2022 |language=en}}</ref>