Confused about how one jammed door can cause so much chaos?
You’re not alone. But forget the officials for a moment. Read a great explainer on Twitter from OC Transpo employee Ken Woods, who is a Rail Traffic Controller. Why doors are such a big deal on the train system.
About train doors...
— Ken Woods (@drivesincircles) October 9, 2019
I have spent quite a bit of time driving trains and troubleshooting all kinds of things with the Citadis Spirit.
There's plenty of conjecture about the tech floating around that really should be cleared up.
First off, the doors indeed have sensors. Look down, you will see a beam-break sensor that prevents the door from closing if you're standing in the door. You will hear the door chime, then a buzz indicating that the door is obstructed. After 3 attempts the door goes into fault.
— Ken Woods (@drivesincircles) October 9, 2019
So what happens in fault mode? Your operator checks CCTV, and if no obstruction is seen, then he/she can manually cycle the doors with a button on the dash. If the obstruction is no longer there, then the doors close and we all get moving... fault cleared.
— Ken Woods (@drivesincircles) October 9, 2019
The second way a door gets obstructed is an object physically preventing the door from closing. Could be a foot stopping it, a bag, or a hand. The result is the same. The door makes a buzz, and opens again just like an elevator. Then it tries to close again. If it closes, we move
— Ken Woods (@drivesincircles) October 9, 2019
In those two instances, should the door not be able to close, your operator can physically close the door on site, and lock the door out with a mechanical lock. We call this Isolating the door. The train recognizes the door as isolated, and we are on our way.
— Ken Woods (@drivesincircles) October 9, 2019
The third reason a door is obstructed is misalignment. This is generally what happens when a person grabs the edge of the door and forcefully opens it against the force of the closing motor. It takes some effort to do this, and it is often catastrophic.
— Ken Woods (@drivesincircles) October 9, 2019
Misalignment means the door sensors report that the door has been taken forcefully out of its mechanical track, and it cannot be manually closed or locked until it has been reset onto its track or recalibrated by a technician.
— Ken Woods (@drivesincircles) October 9, 2019
In many instances, the operator cannot close, manually lock, or isolate a misaligned door. The door will not accept the isolate command because the door cannot be closed in such a way that the physical lock engages.
— Ken Woods (@drivesincircles) October 9, 2019
It takes about 5-7 mins to get from a few attempts to isolate to the realization that the door is actually misaligned and cannot be isolated. The misaligned door is now stopping the train from moving until it is either fixed, or the train is evacuated and the doors bypassed.
— Ken Woods (@drivesincircles) October 9, 2019
Bypassing the doors sounds easy, but it is not. Moving a train with an open door means actually bypassing the communications system of the train (CBTC), making it invisible to the signaling system and other trains.
— Ken Woods (@drivesincircles) October 9, 2019
We recognize that trains are packed right now. It only gets worse with delays, and people on trains cannot always get off in the 24 seconds that is allotted at some stations.
— Ken Woods (@drivesincircles) October 9, 2019
We need to change dwell times when it is busy, and we need to get our trains running on better headways to decrease crowding. These changes are on us, and we are going to fix that.
— Ken Woods (@drivesincircles) October 9, 2019
But, if you take anything away from this as a commuter, let it be this:
— Ken Woods (@drivesincircles) October 9, 2019
Break the beam, not the door.
Stopping a door with a hand is a risk, pulling a door open against the motor can be catastrophic, requiring single tracking around a stopped train and big delays.
We all want the same thing, Ottawa.
— Ken Woods (@drivesincircles) October 9, 2019
A painless, efficient commute.
Thanks for reading.
If you'd like more info on door bypassing, here is the process.
— Ken Woods (@drivesincircles) October 9, 2019
CBTC is the system that allows trains to talk to each other, the track, the switches, and the control center. It is the computerized way that trains use signaling and get authority to move.
CBTC safety systems are designed for efficiency and automation, allowing trains to have really close headways at high speeds.
— Ken Woods (@drivesincircles) October 9, 2019
CBTC also enforces train suitability, meaning the CBTC system will not allow a train to move with a safety issue like an open door.
— Ken Woods (@drivesincircles) October 9, 2019
So, bypassing that safeguard requires us to bypass CBTC, making the train itself invisible to the other trains being controlled by CBTC.
Once bypassed, we have to move that invisible train back to the depot, and prevent other trains from getting too close. A bypassed train can only move at 25kph, and for obvious reasons cannot stop at stations.
— Ken Woods (@drivesincircles) October 9, 2019
So we move the train using written track authorities, and get the train to depot while the normally higher speed system follows behind.
— Ken Woods (@drivesincircles) October 9, 2019
This process takes time, added to the delay time of the door problem itself. (Getting people off the train, troubleshooting, etc).
— Ken Woods (@drivesincircles) October 9, 2019
We will get faster at this part of the problem. But nobody, and I mean nobody, wants the practice.
So that's the short version of it, anyway.
— Ken Woods (@drivesincircles) October 9, 2019
Thanks for reading.
