Tag Archives: twc

Rose Quarter, revisited

I thought I’d do a post on the operational side of what’s going on around Rose Quarter after an out of control car careened into some signaling equipment last week, since the only side the public sees is pretty much just the loss of Transit Tracker and maybe noticing trains stopping more near Rose Quarter. A helpful primer on this would be the original post about Rose Quarter signals just to familiarize yourself with how this area works under normal operating conditions.

One of TriMet’s photos of the scene. Only one car was involved; the blue car in the background is a supervisor’s car that was narrowly missed by everything

The Impact’s Impact on Transit Tracker

Preface: I am not a signal tech and have nothing to do with Transit Tracker, so if anyone who has a better handle on this than me wants to step in and fill in the gaps/correct me if I’m wrong, please, by all means do so. For all the folks reading the news about this and subsequently wondering why Transit Tracker was routed through here or “stored” in this box, this wasn’t a mythical box that Transit Tracker lived in any more than your computer is a mythical box that the internet lives in. Transit Tracker for passengers is more of a nice little byproduct of what this box (and other signal relay boxes like it) did, not its primary purpose. To the best of my understanding, while Transit Tracker for bus is GPS-based (and therefore it was not affected), Transit Tracker for rail has been based on what circuit the train is in. The crash affected power to all of the intersections between Rose Quarter and OCC, and I know that’s affected the signals but I’m not sure the extent to which circuit detection was affected, but because Transit Tracker isn’t working I’m assuming that it was impacted. This is a centrally located section of the alignment that I am guessing is not getting standard data on train positioning, so the Transit Tracker method of locating trains to predict their arrival isn’t functional. Since ALL trains pass between these two platforms (remember that Yellow and Green are the same trains) all lines are affected.

I’m not above criticizing TriMet when I think they make bad decisions or plan things poorly, but I think this was unfortunately a situation in which there was no right thing that TriMet could have done that would have made everyone happy:

  • Some people are saying that sensitive equipment shouldn’t have been in a high-risk area. As far as I know, given that Rose Quarter was part of the original alignment (called Coliseum there), that box or something like it has probably been there since the mid 80s. But as a conservative estimate, we know that the equipment was 16 years old, so let’s say it’s been there since the mid 90s at the latest. This is the first time a car has come careening off of I-5 doing about 80mph ass over teakettle onto the platform, so I’m going to say that this isn’t really a high-risk area, it was the site of a freak accident. I have not heard of any other crashes in that area coming anywhere near close to where the box had been. Besides, it was tied to the alignment in that area – where else are you going to put it?
  • The equipment in the box was so old that replacement parts aren’t available. Fine, it’s old, but you know what? It worked. There’s probably a fair amount of infrastructure in use right now that’s equally old and not easily replaced (I think the fact that TriMet spokesperson Roberta Alstadt said that the delay in replacing it is due to finding something that can communicate with the rest of the system pretty much says that the rest of it, if it fails, can’t be easily replaced either). And just imagine the fits that people would throw if TriMet were to announce they were spending millions to retrofit rail equipment that would make Transit Tracker more reliable or fit all the rail cars with GPS as bus routes are being sliced and 20+ year old buses are on the road. Would replacing this before this incident happened have been the best use of TriMet’s limited money? How about putting GPS on the trains when the circuit location system works? Setting up bollards everywhere a car might fly into something? Yeah, it’d be nice to replace all of the old equipment but I think there are higher priorities for TriMet when it comes to replacing old equipment (e.g. BUSES) than this would have been.

Sure, the loss of Transit Tracker is probably annoying to commuters, but trains are still able to safely pass through this area with minimal delay. If anything, I think this shows a strength of rail in that while a fixed right of way is never going to be as flexible as a bus, there are still workarounds to even major issues like this to keep things moving. So now on to what’s going on here operationally:

Special Instruction 79

Those of you following along at home on the radio have probably heard a lot of trains calling in either from OCC westbound or Rose Quarter eastbound to follow special instruction (SI) 79. Remember that a special instruction is a temporary modification to operational rules that can be in effect for up to a year, versus a train order which expires after 24 hours.

The operationally relevant part of SI 79

And now, in English.

Eastbound trains must stop and call Control from Rose Quarter. For most trains, this will be from the eastbound main platform and signal 18G, though the SI is set up to allow for eastbound moves from the special events track, westbound main or trolley barn as well (for a review of those signals, refer to the previous post on Rose Quarter). Since the signals cannot be called normally through train-to-wayside communication to get a proper to proceed, the automatic train stop (ATS) magnet in the platform will be active and the train will be tripped if the operator tried to go.

ATS trip and bypass counter inside cab of train

Inside each train cab is an ATS counter like the one pictured, which records the number of times that cab was active (i.e., had an operator keyed in and moving forward) and tripped an ATS magnet as well as the number of times an operator has bypassed an ATS magnet. When you bypass a magnet (also referred to as “key-by”), you have 23 seconds to get past it without it stopping your train. Control keeps a record of the totals in these counters for each train car and cab – it prevents an operator from selectively bypassing an ATS magnet or from tripping and continuing without calling it in. You never bypass a magnet without direct authorization from Control first.

So the operator will tell the controller what car and cab they’re in, and what their new bypass number will be. When they have a fresh parallel walk sign on 1st Ave, they will bypass the magnet so they can proceed forward, ensuring that the switch (topmost one in that picture) is not set against the movement since this area does not currently have signal protection, and also ensure that the intersection is clear of any pedestrian or vehicle traffic. The instructions to stop at 2nd and 3rd and then proceed when safe are slightly different from the standard instructions to SOP an intersection, due to the lack of power at these intersections which means they aren’t displaying parallel green lights. Once into the OCC platform, normal operations can resume as points east were not affected by the crash.

Call board at OCC westbound.
There’s one of these at Rose Quarter eastbound as well.

Westbound the procedure is fairly similar. At the OCC platform, operators will call Control and report their car, cab, and new bypass number. The ATS magnet in this direction is up closer to 2nd Ave by signal 18A.

After getting permission from Control to proceed, trains can proceed when safe through 3rd Ave, which is is street immediately in front of OCC when facing west. They must then stop at 2nd to bypass the ATS at signal 18A, ensuring that those switches in the above picture are properly set for a move into the westbound track (or the special events track if directed there). Once at 1st Ave, the operator will make sure that Rose Quarter is clear and wait for a fresh parallel walk sign before continuing into the Rose Quarter platform and then proceeding as normal to all points west.

This special instruction will be in effect until everything through here is fixed, presumably over the next few weeks. Since all of the steps are packaged into the SI, it cuts down on the amount of radio transmissions for everyone – operators don’t have to call in for permission at each intersection after the initial call to Control, and controllers can grant permission to “follow SI 79” without needing to say all of the steps each time a train goes through here.

Window washer rope around pantograph (Photo by Jason McHuff, more here)

Now consider that the RQ-OCC issues were still going on yesterday and SI 79 was in effect when the window washer’s rope took out Red & Blue Line service downtown (which was pointed out to me was once again the unfortunate car 235) and a semi truck hit a Yellow Line train on Interstate, causing trains to be turned around at 7th or Jeld Wen or Jackson or where available.

Semi vs MAX, picture from Twitter

Yes, there were delayed trains and crushed loads for commuters, but the amount of effort required to keep anything moving at all when that many things go wrong is pretty phenomenal. I do think that there are a number of areas that TriMet needs to improve, such as getting word out to passengers in a more timely manner, not pulling in-service buses out in order to bus bridge (or at least not pulling as many – it leaves bus passengers stranded, puts a lot of strain on the buses left in service). But I still think that it’s good for the public to be able to see “behind the curtain”, so to speak, to get an idea of what’s involved on the back end to get people to their destinations when things go wrong.

Call loops

Question: Sometimes when the train stops at a platform, it suddenly jerks forward another foot or so before opening the doors.  Why?

This is an answer in several parts that requires an explanation of train-to-wayside communications.

First, the wayside part.  This is what’s known as a call loop:

Call LoopA call loop (Merlo/158th westbound)

Lloyd Center call loop…and what a call loop looks like when the rail is in pavement.  I forget where I took this, but I think it’s the Lloyd Center eastbound platform

These are located at most platforms on the alignment, as well as at several intersections away from platforms. Hold that thought for now.

Next, the train part.  I’ve never taken any pictures while I was underneath trains in the shop, but there’s a small, sort of wedge shaped device underneath the cab of each train called a transponder (the linked example is not identical to the model that TriMet uses, but it’s close enough).

When that transponder under the train passes over a call loop, it lights up four buttons inside the cab (which are referred to as “Vetag”, sometimes spelled “V-Tag”, which is short for “Vehicle Tagging System”) that the operator can use to communicate with the signals and switches on the alignment.

Vetag console (dark)Vetag, dark (picture taken from coupled end of trailing car)

Vetag lit daytimeVetag, lit (“Call” button not pictured, Old Town/Chinatown platform service)

 

Vetag lit nightVetag, lit at night (bottom left corner) to better show lighting, Beaverton Creek platform service

The first two buttons on that panel (“L” and “R”) are used in the railyards, the third button is used to cancel a command that’s been pressed, and the fourth button which says “Call” is the one most frequently used.  This, by the way, is one of those weird language things of rail – to press that button for a signal can be referred to “calling a signal”, but the word “call” in this context is different from the word “call” when used to refer to communicating with Control over the radio (see also: Call Boards). If you scan the radio, you may also hear this referred to as “selecting a signal”.  Anyway, when the transponder is over a call loop and the Vetag is lit, the operator can hit the call button to get their signal and throw power switches from the cab of the train.

VT on call loopCall loop at Rose Quarter eastbound (VT = Vintage Trolley)

So that’s an explanation of the basics of how a rail operator is able to move the train along the alignment.  Now to answer the “Why does the train sometimes move again after stopping at a platform?” question.

The call “loop” is actually more of a “call figure 8”  I’ve never seen the inside of one, but the circuit inside is kind of shaped like this:Loop circuit

The transponder under the train needs to be over one of the two loops formed by the circuit in order for the control panel inside the cab to light up.  If the transponder is over the spot where the lines of the 8 cross, the control panel goes dark and is unresponsive.  This is known as the “dead spot.”

Picture from MrK (see comments) – LAMTA, not MAX, but same idea 

So what happens when the train stops and then goes forward again at a platform is that the operator managed to stop the train with the transponder directly over the dead spot.  You cannot back a train up on the mainline, so their only option is to go forward – but they can’t go forward too far or they’ll overshoot the call loop completely since they’re already halfway over it.  So they move forward just enough to get the Vetag lit and then immediately brake – which, yeah, can be a bit jarring for a passenger who is expecting the doors to be opening, not to be moving again!

Call loop, OCC WestboundComing in to the platform at Oregon Convention Center, westbound – you can see the call loop between the rails as it passes under the train. Operators have to be able to stop on the loop such that the transponder under their cab is over the right spot of the loop to make their selection.

And since this only happens at platforms with call loops, you won’t get that jerking forward at (most of) the platforms on Burnside, since those don’t use call loops.