Tag Archives: pre-empt

Improving transit speed part 2 – Holladay

A continuation of the last improving transit speed post, which is building off of the discussion over at Portland Transport, and now specifically focusing on people’s suggestions for speeding up travel time along NE Holladay. I hope this provides something of an operational perspective as to why some things are the way they are and that might prove to be a hindrance in redesigning platform placement. These are not necessarily insurmountable obstacles, but are, at the very least, obstacles that prevent any of the suggestions from the Portland Transport post from being enacted immediately.

NE 7th Ave and OCC

Courtesy of Portland Transport, here are weekday passenger counts for eastbound stops on Holladay during fall 2010 (westbound not listed but they’re pretty comparable):

Stop—————–Ons—–Offs
Rose Quarter—–1,207—1,035
Convention Ctr.—–433—–595
NE 7th—————396—–764
Lloyd Center——1,000—1,830

Given those lower passenger counts compared to RQ and Lloyd Center, many people have put forth the argument that Convention Center and NE 7th could be closed to speed up travel time on Holladay without severe impact to passengers.

Not permanently…

However, both of those platforms serve an important purpose on Holladay – not so much for passenger loading, but rather as a necessity to travel along this section of the alignment. The short explanation is that those platforms are needed to call signals/switches on Holladay. The long explanation: keep reading.

For one thing, trains at all stops along Holladay need to call the pre-empt signals to proceed, which will then cascade into the next platform. But OCC & NE 7th have an additional complication. The alignment on Holladay from just past Rose Quarter to just before Lloyd Center is between two sets of switches. On the west (click for map), there’s a crossover as well as switches to diverge into the special events track, westbound main, or trolley barn at Rose Quarter. On the eastern side, there are switches to diverge a train into (or out of) the Doubletree Siding. Going back to my earlier posts on signal types, since all of these switches are in pre-empt territory, they are associated with ABS/pre-empt combination signals and are protected by ATS magnets.

Let’s start with the switches into the Doubletree Siding on the eastern side.

NE 7th Ave

Looking east from NE 7th

The above picture (click for larger) shows what an eastbound train at NE 7th sees. Of interest is combination signal 20A immediately prior to the Lloyd Center platform. The zoom lens makes it look closer than it really is – a better perspective (though not as clear of a photo) is this old picture from when NE 7th was where trains would switch radio channels to Main 1 or Main 3. In that linked photo, 20A is the red light at NE 11th.

In this above photo, you can see that the intersection at 9th is has a permissive white vertical pre-empt. Now look down to NE 11th at the combination signal 20A, which is displaying a yellow horizontal. This informs the operator of an eastbound train at 7th that the power switch that can diverge a train into the Doubletree Siding is aligned to continue east, but 11th is not pre-empted yet. 20A will time out back to a red after a minute, which reactivates the magnet until the next train calls it.

Approaching Lloyd Center, eastbound.
ATS magnet visible in foreground, white vertical on 20A in background.

When 20A is red, that ATS magnet will stop an eastbound train before it gets to the intersection at NE 11th. Therefore, 20A must be called by a train before it can proceed through 11th into the Lloyd Center platform, but it needs a place to call 20A from. Rolling calls, or in other words, pressing the call button as you move over a call loop without stopping, are a poor practice. Trains should be at a complete stop over a call loop to call a signal, so there needs to be some place for a train to stop prior to NE 11th to call 20A, and that purpose is served by the NE 7th platform. When placing the call at 7th, rail operators will look down to 20A from there and make sure it drops from a red before proceeding.

The NE 7th platform is needed for trains to go east to ensure that the switches for Doubletree are properly set, so 7th doesn’t work as a stop that can be closed or skipped since a train will have to stop there anyway to call 20A. (Plus 710 NE Holladay right by the platform at NE 7th is a TriMet building, so it’s unlikely that front-door MAX service is going to go away from there.)

Then over at Oregon Convention Center…

Oregon Convention Center (OCC)

West from Convention Center

Looking at OCC on the western side of the Holladay alignment, there are two combination signals that affect train movement from OCC to into Rose Quarter: 18A and 18B.

Signal 18A is located on the corner of NE Holladay & 2nd for westbound trains. It is associated with switches 13A, 11C, and 11D and the ATS magnet (visible in the above picture as the little yellow square) on the opposite corner of NE 2nd. If any of those switches are not properly set for a westbound move from OCC or if there is a conflicting move in progress – for example, a vintage trolley coming out of the trolley barn or turnbacks like last weekend’s streetcar work, 18A will remain red and a westbound train will be tripped at the ATS magnet. To proceed through here, 18A needs to be called by westbound trains from a platform (remember, no rolling calls), which is why OCC is needed.

West from OCC, 18B visible (displaying a red aspect, click for larger and look on the Rose Quarter platform)

Way down there by the Rose Quarter special events platform is signal 18B, an ABS/pre-empt combination signal that routes a train into the westbound main (click for a more up-close picture of 18B), the special events track, or the trolley barn. Like 18A, 18B is called by westbound trains from OCC, and both need to drop from reds before a train can continue west into Rose Quarter. 18B doesn’t have an ATS magnet of its own (the magnet at 2nd for signal 18A will stop a train before it gets near 18B) but this signal is still necessary for route selection. Both 18A and 18B will time out back to reds and will need to be called by the next westbound train, ensuring that the switches are properly set and there are no conflicting moves by other trains. As a result, OCC is another platform that can’t be skipped or closed because westbound trains need a platform to call 18A and 18B from. Similar to NE 7th, since trains have to stop here anyway to call the signals, they may as well service the platform.

White vertical on 18A, yellow horizontal on 18B

So can either of these stops be closed, moved, etc? Not easily.. NE 7th eastbound and OCC westbound are currently necessary to call their respective ABS/pre-empt combination signals to ensure switch alignment/no conflicting moves by other trains. And while their corresponding westbound and eastbound platforms don’t have combination signals, operators will still call for pre-empt signals to proceed from there. At present, I don’t really see a way to avoid stopping at both of these platforms despite the relatively low passenger on- and off-boarding at these locations. This isn’t to say that it can’t ever be done, but I don’t think skipping either of those platforms can be done as an immediate fix.

SOPing an intersection

In my last post about the mall, I mentioned how the intersections on the mall have secondary call loops, that is, call loops that are not located at a platform. Normally, operators don’t need to use these because the signals will be cascading from when the pre-empt at the platform was called. Secondary call loops are there to be used if the signal times out before the train gets to that intersection – they allow operators to quickly recall the signal to keep moving. That’s not the only way to get a pre-empt again – as I’ve mentioned before, some intersections are equipped with a push button, where an operator can reach out of the cab window and use the push button to recall the pre-empt.

However, not all pre-empted intersections have push buttons or secondary call loops. For example, on most of Burnside (which uses mass detectors instead of call loops) a train cannot get a permissive signal again if the pre-empt times out or fails to display a white vertical. Continuing through the intersection on a yellow horizontal is the equivalent of running a red light for a train – it’s a rule violation and it’s dangerous.

Stop

So if it should happen that a pre-empt times out or fails to change to a white vertical in the first place, and an operator has no secondary call loop or push button, there is a set standard operating procedure (SOP) to safely proceed through the intersection. If you’re listening to the radio and you hear an operator requesting permission to SOP the intersection, what they’re asking for is clearance to proceed on a yellow horizontal.

First, the operator has to stop the train before entering the intersection on a yellow horizontal. Next, they call Control for permission to SOP the intersection. If it is an intersection that can be safely SOPed*, Control will tell the operator to wait for a fresh parallel green and walk sign. Where applicable (e.g. on Burnside) the operator will also have to wait for a red left turn arrow.

*Not all intersections can be safely SOPed – here heading west into Goose Hollow, Collins Circle at 18th & Jefferson has a secondary call loop. However if an operator overshoots it, they will not be able to SOP the intersection

When the auto traffic lights have a parallel green and red left turn, the rail operator will  sound horn warning and proceed when safe. This includes checking for emergency vehicles. As seen from 2005, an emergency vehicle’s Opticom can’t make a white vertical go back to a yellow horizontal, but if they placed their call before you it will prevent a white vertical from coming up at that intersection.

Train vs Fire Truck, Hillsboro, 2005.

Open response to an open letter

I recently saw this complaint on Planet Feedback:

Tri-Met Train Engineer Refused to Open Train Doors

Posted Sat February 5, 2011 3:03 pm, by John T. written to Mr. Neil McFarlane, General Manager, Tri-Met

I am writing to inform you of an unpleasant experience on the Yellow Max Line to Expo Center. This is the text of my Tri-Met website email complaint, which I sent on 1/28/2011:
Engineer refused to open the door (Train 123, 1:28 p.m., Thursday,1/27/2011 at SW 6th Ave. & Morrison), even though there was ample time to do so. I crossed the street from Pioneer Square as the Expo Center train was stopped at a red light. When my light changed to green, I immediately crossed the street and quickly walked right in front of the stopped train, so the engineer had to see me. I hurriedly pressed the yellow and blue buttons for the doors to open on the first car. The traffic light was still red (for the train). They did not, so I attempted to open the doors with my fingers. Seeing the doors were tight and unyielding, I immediately removed my hands and stepped back. A second or two after I had stopped trying to open the doors, the engineer said over the external speaker, “You better take your hands off that door or you will be arrested.” Those words prove he had seen me while the train was still stopped. A few seconds later, some stranger walked up to me and said he had pushed the door open buttons too in the second car, and the doors did not open. The train was still stopped as he initially spoke to me. Both myself and the stranger were casually well-dressed and very sober. Generally speaking I like Tri-Met, but this engineer was out of line and needs retraining and/or some other appropriate sanction. I wonder how many other riders he has treated so poorly.

Please investigate the matter and the Rider Complaint procedure thoroughly, which appears to be deficient and in need of revision because of the following: The Tri-Met website did not generate a case number or any email to me with a copy of my issue after I sent it on 1/28/2011. Also, since I did not receive a timely confirmation via email or telephone after 1/28/2011, I sent an email on or about 2/3/2011. On 2/4/2011 I received an email (copy enclosed) stating that my issue was reported on 1/28/2011 to the Yellow Line Manager, and that it is a “private matter” between the manager and the employee. I am not satisfied with this closed system, as there is no real accountability to the public or myself. The public is supposed to trust what occurs behind closed doors, but we are not even informed of the outcome. This does not seem fair.

I was pleased to see the comments to the letter, where several people explained that once a train has its signal, it can’t wait for more people to board. Another commenter said it’s not appropriate to release disciplinary information to the public, which I also agree with. However, as for the original complaint, I know that John T is not unique in being mad that trains don’t wait for him and even though I’ve already written about the yellow door release buttons before, now’s as good a time as any to do it again, as well as explain a little bit about how the mall signals work.

First, a basic refresher on pre-empt signals – these display a yellow horizontal which means “STOP” to a train or a white vertical which means “PROCEED WITH CAUTION”. Because of how the CBD is set up, there are a number of intersections where auto traffic will have a red light (STOP) but a train will have a white vertical – this will be the case in any intersection where a green light could potentially turn a car into the path of a train.

SW 6th & Yamhill – red light for cars, white vertical for an eastbound train, and walk sign for pedestrians

So don’t look at the auto traffic signals to determine if a train is about to move or not, because at most intersections the train isn’t following those signals. The train having a “red light” in this case is irrelevant.

Now moving on to the rest of the complaint, which is essentially “the train didn’t wait for me and reopen the doors.” Well, no – the mall is not a good place for that sort of thing. Sometimes an operator of a north or southbound train will release the doors – that is, turn on the external door buttons so that passengers can push them to open the doors and let themselves on – if they are waiting for an eastbound or westbound train to pass or for the way ahead to be clear, but once they’re ready to call the signal, the doors are closed and it’s time to go. Here’s why:

Pioneer Courthouse, SW 5th & Yamhill facing south

This is a view looking south on 5th Avenue. On the top of the pole in the middle of the picture, you can see the pre-empt signal for southbound Yellow and Green trains to PSU. It’s displaying a yellow horizontal in the picture which is the default aspect until a train calls it. Now look down 5th at each intersection – you can see the auto traffic lights that are red and green on the left side of 5th, and on the right side you can see the pre-empt signals for the trains (all yellow horizontals).

SW 5th & Yamhill, wider view.
The pre-empt signals may be easier to see in this picture

If you ride a train on 5th or 6th, you’ll notice that ideally the train will only stop at platforms, not at the intersections between platforms. This is because those pre-empts cascade – an operator will call the signal at the platform, and then the pre-empts up through the next platform are automatically timed so that when the train gets to each intersection, the pre-empt will be displaying a permissive white vertical to proceed without the operator needing to do anything. In the event that the train has to stop (e.g. a personal auto blocking the right of way, a pedestrian running in front of a train, a car or cyclist running a red light – you know, those things that never happen) each intersection also has a secondary call loop where an operator is able to recall the signal. Under normal operating conditions, the cascading signals between platforms allows for the smoothest and fastest train movement.

South end of the mall by PSU looking north up 6th Ave. Notice the pre-empt signals on the right, the curve in the rails for the train to move to the center lane, and the bus ahead pulling away from its stop

But remember that the mall isn’t just for trains. The alignment runs serpentine with buses so that the trains and buses leapfrog up and down the mall with the rails cutting over to the right every few blocks for a platform, and then back over to the center lane for the blocks that are served by buses. The auto signals on the mall are in sync with the train pre-empts, so buses will be held on a red light to let the train move through and get out of the way when the train has a permissive signal since both buses and trains share the center travel lane and cross paths to service alternating blocks.

View from above of a Yellow Line train on 5th moving into the center travel lane after servicing the Pioneer Courthouse platform in the previous block

SO – getting back to why a train can’t wait “just a few more seconds” for you and reopen the doors… when an operator calls a signal at a platform on the mall, it starts the cascade of pre-empts up to the next platform. This cascade goes through even if the train stays put where it is, which can happen if the operator reopens the doors to let late runners on and then the signal in front of them times out. This delays buses unnecessarily as they are held at red lights waiting for a train that isn’t there. As a result, not only will the train you wanted to get on be delayed, but so will a bunch of buses because you weren’t at the platform when the train’s doors were open. Preventing that from happening, quite frankly, isn’t something an operator needs to be disciplined for.

And finally, I feel the need to defend the operator of that train – I know whose run that is and they’re one of the last people I could think of that would threaten a passenger with an arrest. I’m hard pressed to believe that such a comment was even made by the operator, but I’m not surprised at the accusation. I have seen operators scapegoated for everything that goes wrong for passengers (classic example – a bus running exactly on time and someone on the bus calling their boss “Yeah, the stupid bus was late again so I’m going to be late for work.”  Hey! Not the bus operator’s fault you picked a later bus than you needed. Take responsibility for your own actions.)

Washington Street

Washington Street in Hillsboro

Washington Street is the pre-empted area at the western end of the Blue Line. In this picture, you can see the pre-empts (all yellow horizontals since there are no trains moving through) on both sides of each intersection, though they’re a little easier to see on the left. Also in this picture, the way the overhead wire zigzags is clearly visible – remember this is done to evenly wear down the carbon shoe on the pantograph.

MAX-eye view

I haven’t posted any video in a while, so here you go. Eastbound from 1st and Morrison to the Rose Quarter, filmed a few years ago.