Tag Archives: train to wayside communication

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.

More complicated than you think

The folks over at Portland Transport recently had their annual Q&A session with TriMet GM Neil McFarlane. A question that came up, as it has before, was about improving MAX speed and efficiency by closing some stops. This led to a follow-up post at Portland Transport (and is making me revisit the series I’d done on the same topic but never finished) and while working on a post for that, I dug out this map of the area around SW 10/11th and Yamhill/Morrison where the Portland Streetcar crosses the eastbound & westbound Red and Blue MAX alignment.

I’m posting it here because it’s a good illustration that shows how there’s a lot more involved in closing/moving a stop than just laying down tactile strip and moving the fare machines. It’s the work involved in changing the track circuits, moving the train-to-wayside-communication (TWC) call loops, reconfiguring signals, etc that would be a barrier as far as expense (and complexity!) is concerned.

Quick explanation since this map introduces something I haven’t mentioned before:

Many readers here will already be familiar with how the operator of a MAX train will press the “Call” button on the console when the transponder under their cab is over a call loop to call their signals and throw power switches in order to proceed. However, by design, that transponder will call some signals without action on the part of the operator. So for example as shown in the map below, signal W6, which is an ABS/pre-empt combination signal for eastbound trains, is not called by the operator doing anything, but is instead called by the train just before SW 13th when the transponder under the lead cab passes over that TWC loop.

This map is outdated – trains do not regularly go through 11th Ave anymore, and each of those tracks have their own signal now instead of all using signal W4, but I still wanted to post it here because it nicely shows the complexity of what otherwise appears to be a fairly simple layout.

Can’t remember if it had been a test question or a Rail Rodeo question that went something like “There is a Yellow Line train in 11th Ave, an eastbound Blue Line at 14th, and a southbound streetcar at Washington. If the Blue Line crosses 13th before the Yellow Line gets their call on, when will the streetcar get their signal?” which reminded me too much of those math problems from high school, where if Mary is on the 9pm train heading due north at 55mph, what time will she pass John’s train which is heading south at 60mph?

Train numbers, route codes, and more with signals

Question: How does a train know where to go?

This question comes up a lot, and although I’ve answered it in comments or emails or Twitter, I’ve never given it its own post. But a lot of people have asked, for example, if a train is eastbound at Gateway, what do you do to it to send it to Gresham vs the airport vs Clackamas? Sure you call the signal but how do you get the right aspect(s) to come up for where you want to go? It’s not like the trains have a steering wheel.

(Actually it’s kind of fun to let kids see the cab of a train at the end of the line and ask them where the steering wheel is. It stumps their parents too!)

It’s a trick question.  Here’s the “steering wheel” of a MAX train:

Route code (and train number, which is blurred out, you don’t need to know what train number this was, but in following safety procedures, I assure you the train was stopped at the end of the line – not only was it not moving it wasn’t even keyed in), Type 2 thumbwheels

In the cab of each train is a place to set the train number (under normal operating conditions, this won’t change over the course of the day) and also the route code. The train number is the train’s identifier, and it matches the number visible in the window box – for example, the train in the old header picture of this blog was train 40; the train in the old background image was 71. If Control wants you, they’ll call your train number over the radio. If you need something, you begin a radio call to Control by stating your train number.

You can tell what yard a train is from (though not necessarily what yard the operator is from due to reliefs) and what color its route is from the train number. Trains 1-15 are Blue originating out of Ruby, 20-38 are Blue out of Elmonica, 40-53 are Red out of Elmonica, 60-74 are Yellow/Green out of Ruby, and the Mall Shuttle had been train 89 out of Ruby. Trains not regularly scheduled, such as those used for testing or burn-in get numbers in the 90s. There are some exceptions to this breakdown, like train 10 is Blue most of the day but becomes Red at night, 43 begins its day going from Elmo to PDX to Hatfield before becoming a regular Red Line, but this is all pretty much just trivia for passengers anyway, it’s not like I’m going to quiz you on this later.

The route code is what tells the train where to go from its current location. Every possible destination on the alignment that can be reached via power switches has a route code assigned to it – not just the ends of each line, but also the yards, sidings, pocket tracks, etc.

Sign at Galleria with 11th Ave route code

In the first picture in this post, a route code of 50 will get a train to either track 1 or 3 in the Jackson turnaround by PSU, whichever is open. Every time an operator places a train-to-wayside call over a call loop, the switches will be set to move the train toward the destination set as the route code, and the corresponding signals will be displayed. Operators are responsible for ensuring the route code is correct for where the train is supposed to go. For Blue and Red line trains, this is pretty easy – the cab that leads going east will be set for Gresham or PDX, and the cab that leads west will be set for Hillsboro or BTC so it does not need to be adjusted frequently (well, it’s easy as long as Red line operators don’t forget to change the route code from the BTC pocket track on the last trip and end up in there when they need to keep going west…).

Yellow/Green line trains are a little trickier. For trains leaving Ruby to service those lines, depending on which run it is the route code will be set for Expo, the Jackson turnaround, or the Gateway auxiliary track (where the operator will swap cabs and take the train to Clackamas). Then to change color at Jackson, the operator will leave Clackamas (for example) with the route code for the Jackson turnaround, and then once there will set the route code for Expo. When leaving Expo in the other cab, they’ll set the route code for Jackson, and then once in the Jackson turnaround, they’ll change the route code for Clackamas. Potential errors can happen if an operator forgets to change the route code from 50 when leaving Jackson (if that happens, the train will head back south to PSU from Union Station instead of crossing the Steel Bridge) or forgetting to set the route code for Jackson from the end of the line (so for example, heading toward Clackamas from Interstate Rose Quarter instead of over the Steel Bridge).

Signal aspect review

Signals will reflect what route code is in your thumbwheel. First, here’s a quick overview  of signal aspects (for more information, I’ve written a lot about signals already)

A red aspect – STOP

A yellow aspect – clear for one ABS block (that is, the distance to the next ABS signal) on the primary route

A green aspect – clear for two ABS blocks on the primary route

A lunar aspect – proceed with caution, tracks may not be clear (your switches are set but no indication of train occupancy ahead)

The number of aspects that are lit indicates which route you’ll be going on (one aspect = primary route, or “A” route. Two aspects = secondary route or “B” route. Three aspects = tertiary “C” route, etc). As an operator, when you’re looking at a signal that can display more than one route, you need to know which of those routes corresponds with the route code you have in your thumbwheel.

Back when I was first learning the signals, one of the most confusing parts for me was confounding signal aspects with switch positions, in part because yellow over green signals are referred to as “advanced diverging” and red over yellow are referred to as “diverging” – so that means when you see one of those signals, you can expect switches to be set diverging, right? Well, not necessarily…

For example, at the ends of the lines (here into Cleveland Ave from Gresham TC) a single yellow aspect will actually put you over diverging switches into Cleveland, but a red over yellow is a straight shot in. A signal with two aspects means that you’re diverging from the primary route, but not necessarily diverging over switches – it could be that the primary route itself diverges over switches but the secondary route goes straight. I had been thinking about the ABS signals in terms of switches, not routes, and that was a stumbling block for me. A permissive signal indicates that your switches are set for whatever your route code is, but you have to know if that means they’re diverging or normal.

Same with this red over white vertical on W1760 at Hatfield – it’s a secondary route (2 aspects), but this train will be going straight in, not diverging over the switches. Sorry for the blurry picture but it’s the only one I have.. I either need to go out there and get a clearer one or get someone to do that for me.

It’s not where you are, it’s where you’re going

So keeping in mind that an ABS (or ABS-pre-empt combination) signal displays your route, here’s an example of what it looks like when you can call the same route from two different locations. Take a look at these signals:

Signal 76: Red over red over green
Clear for 2 ABS blocks to Clackamas TC

Signal 78: Red over red over yellow
Clear for 1 ABS block to Clackamas TC

Both trains that called these are facing east at Gateway – the one looking at signal 76 is in the eastbound main; the one looking at signal 78 is in the pocket track. Both have a route code set for Clackamas TC. And from both tracks, that’s the “C” route / 3rd route / tertiary route, which is why both signals are showing 3 aspects. These aspects are almost functionally identical (the yellow on 78 just means that this train’s leader is only one ABS block ahead of them, otherwise that would’ve been a green) even though the train observing signal 78 has two more sets of switches to diverge over to get to the eastbound main to get to Clackamas.

Gateway from above, click for larger

The platforms are in the bottom of the picture – from left to right, that’s the westbound mainline, pocket track, and eastbound mainline. Notice that to get over to the eastbound main alignment (which, out of range of the top of the picture, diverges off to Clackamas) a train in the pocket track has to pass over the switches that could otherwise bring it to the auxiliary track, and then over another set of switches to join the eastbound main. Yet its signal aspect at Gateway to get to Clackamas is identical to what a train in the eastbound mainline would get, even though the train in the eastbound mainline doesn’t have to worry about those switches.

Where a train is starting from doesn’t matter – where it’s heading is what will be displayed on the signal.

Lunar on signal 78, eastbound from Gateway pocket track

Lunar on signal 76, eastbound main at Gateway

Similarly, a train with a route code for Cleveland (or the Ruby Yard) going east from the pocket track will get a single lunar aspect on signal 78, just like how a Blue Line train heading east at Gateway will have a lunar on signal 76, even though a train starting from the pocket track has to diverge over switches to get there. The signal indicates that the switches are set for the route code in  your thumbwheel, but you have to know if that means the switches are set normal or diverging (because you do NOT take a train at a high speed over these diverging switches!)

Here’s another example, eastbound at Beaverton Transit Center.

Signal W760 is for a train in the pocket track (which is typically a Red Line), and W754 is the signal for the eastbound main. A train heading east from the pocket track will have to diverge over switches to get into the eastbound main, yet the ABS signal will show a single aspect indicating the primary “A” route. It doesn’t matter where the train is at, it matters where it’s going – and for trains in either track here, the only place to go is the eastbound main (primary route), therefore both signals have a single head that can only display a single aspect. There is no choice of route from either track, even though you will be diverging into the main eastbound track if you are leaving the pocket track.

W556 at Sunset, for a Red Line train heading to the BTC pocket track

On the other hand, if you’re headed west into BTC, you do have a choice of two routes (along the westbound mainline or into the pocket track), which is why signal W556 at Sunset and the intermediate signals leading into BTC (W616 and W716) can all display one or two aspects for a primary or secondary route. The signals will indicate that the switches are set for whichever of those route codes you have in your thumbwheel.

You know, I don’t know how to end posts. I feel like I should assign a 2-page essay on the importance of ensuring you have the right route code in your thumbwheel and how that relates to ABS signal aspects. Show your work.

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.