ION - Waterloo Region's Light Rail Transit

[trainspotter139]

I read an article which said that any train with a door that wouldn’t close would be locked out by the ATP (automatic train protection) and could only be moved under old-school procedures essentially involving written authorization to use sections of track.

Total engineering fail; ATP has no business absolutely preventing a train from operating just because of door problems. There should be a procedure to inform the system that the door has failed, possibly install a temporary barrier, and continue on, even in service if appropriate.

What horrors lurk in the design away from areas where I can confidently assert the designers screwed up?

I hope this isn’t the way of the future: software industry practices applied to other industries. By this I mean products which, while technically meeting the spec, fail to operate in the way which anybody who actually thought about the problem for a few minutes would realize they should operate. The customer should not be responsible for thinking of all the obvious, goes-without-saying, features and putting them explicitly in the spec.

1. I think you are mixing up ATP with ATC. ATP is just a signaling system that compares train speed with permitted speed and signals the train control computer for brake activation if the train speed is above the permitted speed. ATC takes control over acceleration and braking and works in conjunction with ATP to operate the train safely.

2. That's not an engineering fail at all. All modern passenger trains have a door interlock braking system. When the doors are open, the brakes are activated. When the doors close properly the brakes are then deactivated. If the doors do not close properly, the door interlock brake stays active. ATC is a completely separate hardware module that simply sends commands to and receives data inputs from the train control computer. ATC doesn't get a signal as to why the brakes are active. All ATC gets from the train control computer is basically: "Brakes: Active, Position: Service-50%, Locked: True". ATC would operate in the same fashion if the operator hit the emergency stop switch on the control panel. All ATC would know from that is: "Brakes: Active, Position: Emergency, Locked: True". ATC can only control the train if the controls aren't locked out by another module with higher control priority, like the emergency stop switch or door interlock brake.

[ijmorlan]

1. I think you are mixing up ATP with ATC. ATP is just a signaling system that compares train speed with permitted speed and signals the train control computer for brake activation if the train speed is above the permitted speed. ATC takes control over acceleration and braking and works in conjunction with ATP to operate the train safely.

I think you’re right. It’s been a while since I read the article; most likely it referred to ATC.

2. That's not an engineering fail at all. All modern passenger trains have a door interlock braking system. When the doors are open, the brakes are activated. When the doors close properly the brakes are then deactivated. If the doors do not close properly, the door interlock brake stays active. ATC is a completely separate hardware module that simply sends commands to and receives data inputs from the train control computer. ATC doesn't get a signal as to why the brakes are active. All ATC gets from the train control computer is basically: "Brakes: Active, Position: Service-50%, Locked: True". ATC would operate in the same fashion if the operator hit the emergency stop switch on the control panel. All ATC would know from that is: "Brakes: Active, Position: Emergency, Locked: True". ATC can only control the train if the controls aren't locked out by another module with higher control priority, like the emergency stop switch or door interlock brake.

It is an engineering fail for a door problem to absolutely prevent operation of the train.

To be clear, there are multiple possible scenarios. Say the door is stuck and won’t close; either at all or completely. Depending on the exact situation, either the vehicle should be evacuated and then driven to the OMSF, or kept in service until the end of the line (or wherever) with a temporary barrier across the door (and the door excluded from normal open/close operation). In either scenario, there needs to be a procedure to inform ATC that the door is locked out and to ignore what it is saying.

Another possible scenario is the door closes fine, but the device which detects the state of the door has failed and always reports that it is open. In this scenario especially it is obviously totally absurd for the vehicle not to be able to operate.

Even with the current malengineered situation, the train can be operated; it just needs written track authority. So presumably there is a way of disengaging the brakes even while the door is still reporting that it is open (I don’t think typical train motive power is capable of moving the train against a fully-applied brake, even if the control system would allow an attempt). Again, a door problem is not a legitimate reason to require going back to 1800s technology. In fact, I can’t think of much that would; besides the obvious failure of part of the ATC itself, something like total brake failure maybe; except that then the vehicle would have to be towed or pushed, and in that case it would be nice if ATC could still be able to operate the helper vehicle.

This is not the first time I have heard of clearly wrong design related to doors. My understanding is that some subway trains, I think including the TTC’s Toronto Rockets, have the following procedure when an obstruction prevents a door from closing: all doors re-open and repeat the closing sequence. If they fail 3 times, the train is out of service. This is totally absurd. What should happen is that only the obstructed door should re-open. This means instead of requiring 24 doors to successfully close simultaneously, maybe 23 close on the first try and the remaining one re-opens and then closes. So right away this would eliminate most of the problems. Next, the basic idea of 3 failures requiring taking the train out of service is OK; if there is an equipment failure, at some point it needs to be dealt with. But if the reason is identified as “some idiot kept sticking their foot in the door”, then there is no equipment failure (not even a suspicion of a failure) and no point in taking the train out of service. What, they’ll take it back to the yard, and do … what? It’s fine; there was just somebody blocking it.

I think safety engineers need to step back more often and consider whether the behaviour they are creating is reasonable. I’m not asking for them to design unsafe systems, but the above examples just don’t pass the smell test.

[tomh009]

This is not the first time I have heard of clearly wrong design related to doors. My understanding is that some subway trains, I think including the TTC’s Toronto Rockets, have the following procedure when an obstruction prevents a door from closing: all doors re-open and repeat the closing sequence. If they fail 3 times, the train is out of service. This is totally absurd. What should happen is that only the obstructed door should re-open. This means instead of requiring 24 doors to successfully close simultaneously, maybe 23 close on the first try and the remaining one re-opens and then closes. So right away this would eliminate most of the problems.

This is the way every urban train (that I can think of) works: all the doors open and close in unison. One won't close? All doors will reopen and attempt to close again.

I am not an expert in this, though, so I don't know why this logic is used.

[jamincan]

This is not the first time I have heard of clearly wrong design related to doors. My understanding is that some subway trains, I think including the TTC’s Toronto Rockets, have the following procedure when an obstruction prevents a door from closing: all doors re-open and repeat the closing sequence. If they fail 3 times, the train is out of service. This is totally absurd. What should happen is that only the obstructed door should re-open. This means instead of requiring 24 doors to successfully close simultaneously, maybe 23 close on the first try and the remaining one re-opens and then closes. So right away this would eliminate most of the problems.

This is the way every urban train (that I can think of) works: all the doors open and close in unison. One won't close? All doors will reopen and attempt to close again.

I am not an expert in this, though, so I don't know why this logic is used.

It's standard for any system where the doors opening/closing is automatic for obvious reasons. ION is an example that clearly shows that train manufacturers already have the technology to individually control the doors. You end up trading one problem for another, though. Instead of a simpler system where all doors operate simultaneously, you have a more complicated system that could now fail in some other way.

[ijmorlan]

It's standard for any system where the doors opening/closing is automatic for obvious reasons. ION is an example that clearly shows that train manufacturers already have the technology to individually control the doors. You end up trading one problem for another, though. Instead of a simpler system where all doors operate simultaneously, you have a more complicated system that could now fail in some other way.

I assume it’s inertia. At one time, it would have been a substantial undertaking to build any sort of independent control into the door system. First you need a way of getting per-door signals from the cabs to the doors; and next unless the individual operation is entirely automatic you need some way of providing controls for each door. But now, with everything computerized, it’s much easier to push all the complexity into software. This doesn’t make the problem disappear entirely, but providing the individual control becomes a coding problem, rather than a whole bunch of additional hardware.

One thing I’d like to know: does the cab display show the status of each door individually? I don’t actually know.

Although it occurs to me that if the open/close cycle were localized to each door then the overall train could simply have a single open/close command for all doors, even while individual doors can retry on their own. There is no need for a door that won’t close to immediately tell the rest of the train about it — until it’s given up on retrying, it can just signal that it’s still closing and so it will appear as a very slow closing door to the rest of the system. But I’m less sure about this part because I don’t know where the logic to re-open and then try closing again actually is — in the door mechanism or in a central control point. In a modern system it doesn’t matter though.

[ijmorlan]

The mention of ION reminds me of another door-related example of maldesign: when the LRT is sitting in station with the doors in “open when button pressed” mode, each door chimes when it closes after letting somebody on or off. This leads to an utterly pointless cacophony. Instead they should close silently. The chime is only useful when the reason the doors are closing is because they are changing to “closed, ready to move” mode. Arguably the chime should also sound just before the doors switch from “ open when button pressed” mode to “closed, ready to move” mode.

Additionally, the doors should have different re-opening policies depending on why they’re closing: if they’re closing because enough time has elapsed since the button was pushed, they should re-open like an elevator door: essentially, prioritize letting people through. Only once the doors have been informed to close in preparation for departure should they switch to the more aggressive subway train policy which prioritizes getting the train under way (and then, of course, see previous discussion on allowing each door to have more independence).

[danbrotherston]

The mention of ION reminds me of another door-related example of maldesign: when the LRT is sitting in station with the doors in “open when button pressed” mode, each door chimes when it closes after letting somebody on or off. This leads to an utterly pointless cacophony. Instead they should close silently. The chime is only useful when the reason the doors are closing is because they are changing to “closed, ready to move” mode. Arguably the chime should also sound just before the doors switch from “ open when button pressed” mode to “closed, ready to move” mode.

Additionally, the doors should have different re-opening policies depending on why they’re closing: if they’re closing because enough time has elapsed since the button was pushed, they should re-open like an elevator door: essentially, prioritize letting people through. Only once the doors have been informed to close in preparation for departure should they switch to the more aggressive subway train policy which prioritizes getting the train under way (and then, of course, see previous discussion on allowing each door to have more independence).

Is this not an accessibility feature to let all people know that the door is closing?  I.e., it is about the door closing, not the train departing.

[KevinL]

Indeed, its primary purpose is to assist the visually impaired so they don't get caught in a closing door.

[ijmorlan]

Indeed, its primary purpose is to assist the visually impaired so they don't get caught in a closing door.

And yet somehow elevators get by without it. Or, now that I think about it, do elevators have a closing chime? Even if so, however, it’s not as loud and obtrusive as the LRT chime. The LRT chime is totally fine for departure, it’s just the repeating of it over and over while the LRT is parked which I find to be excessive.

[bgb_ca]

Indeed, its primary purpose is to assist the visually impaired so they don't get caught in a closing door.

And yet somehow elevators get by without it. Or, now that I think about it, do elevators have a closing chime? Even if so, however, it’s not as loud and obtrusive as the LRT chime. The LRT chime is totally fine for departure, it’s just the repeating of it over and over while the LRT is parked which I find to be excessive.

Could that possibly be resolved by using the button to open if necessary but control the close from the cab? (Kinda a hybrid of what they do now?)

[PhilippAchtel]

Even with the current malengineered situation, the train can be operated; it just needs written track authority. So presumably there is a way of disengaging the brakes even while the door is still reporting that it is open (I don’t think typical train motive power is capable of moving the train against a fully-applied brake, even if the control system would allow an attempt). Again, a door problem is not a legitimate reason to require going back to 1800s technology. In fact, I can’t think of much that would; besides the obvious failure of part of the ATC itself, something like total brake failure maybe; except that then the vehicle would have to be towed or pushed, and in that case it would be nice if ATC could still be able to operate the helper vehicle.

There's certainly a way to disable the door interlock to move or tow a vehicle back to the yard for repairs, but it would never be engaged with passengers on board for obvious reasons.

You'd never be able or want to tow or operated a train or any other vehicle with its brakes engaged. Brakes are designed purposefully to be much more powerful. But there will also be some mechanism or master switch to manually disengage the emergency or parking brake.

[ac3r]

Indeed, its primary purpose is to assist the visually impaired so they don't get caught in a closing door.

And yet somehow elevators get by without it. Or, now that I think about it, do elevators have a closing chime? Even if so, however, it’s not as loud and obtrusive as the LRT chime. The LRT chime is totally fine for departure, it’s just the repeating of it over and over while the LRT is parked which I find to be excessive.

Most elevators don't have a chime, but most have sensors in the doors that will reopen them if something obstructs them during the close cycle unless it's an extremely old elevator. Next time an elevator door is closing, wave your hand out and it'll reopen.

[danbrotherston]

And yet somehow elevators get by without it. Or, now that I think about it, do elevators have a closing chime? Even if so, however, it’s not as loud and obtrusive as the LRT chime. The LRT chime is totally fine for departure, it’s just the repeating of it over and over while the LRT is parked which I find to be excessive.

Most elevators don't have a chime, but most have sensors in the doors that will reopen them if something obstructs them during the close cycle unless it's an extremely old elevator. Next time an elevator door is closing, wave your hand out and it'll reopen.

Most elevators don't have a chime because most elevators are >15 years old. New or refurbished elevators all must include a chime.

[ijmorlan]

There's certainly a way to disable the door interlock to move or tow a vehicle back to the yard for repairs, but it would never be engaged with passengers on board for obvious reasons.

I don’t see why an LRT can’t be operated with passengers with a door locked out. If the door can be completely closed and then locked in that position, then just put a sign on it so people know not to use it; if it can’t be 100% completely closed/latched, then install a temporary purpose-designed barrier (basically a tarp with hooks/loops to hold it in position). Depending on the vehicle and train, evacuating one compartment or car could also be an option.

But that being said, in Ottawa they don’t just have to offload passengers which I will acknowledge is often a reasonable approach (just put them on the next train; presumably door problems don’t happen so often that many people will be severely inconvenienced); they then have to move the train under written train orders, which is absurd.

[GarthDanlor]

And, whatever the actual numbers, we should remember that the LRT was built not only to carry people but also to promote intensification along its route. 

Exactly and initially, I think, intensification was expected to be the most important job of the ION.  Ridership will continue to develop as a result. By all objective measures, the ION project has led to intensification(and presumably will continue to do so).

As for the numbers it pretty hard to gauge success or fail on the the first year of operation especially when part of the year fell during a pandemic....