APACU

And now, back to your regularly scheduled (more or less) technical posts.

All about the announcements

“Pioneer Square. Doors to my left. TriMet ticket office and visitor information available weekdays. Bus and MAX service on 5th and 6th Avenues”

APACU, Type 2

AACP, Type 4

The audio and readerboard announcements and external signs on the trains (Types 2, 3, and 4) are controlled via the APACU in the train, or Automatic Passenger Announcement Control Unit. In the Type 1 trains, the external signs are all manually scrolled and there are no readerboards, but the audio announcements are still set through the APACU (which will also set the readerboards and signs in  your trailing Type 2 or Type 3). In the Type 4s it’s actually called the Automatic Announcement Control Panel, but since AACP isn’t an especially pronounceable acronym and I’m old and resistant to change, we’re sticking with APACU.

Excerpt from Blue Line Paddle

The APACU is typically programmed at the ends of the lines, though it can also be set mid-route when necessary. The above picture shows part of a paddle, or schedule, for a Blue Line train. The #99 refers to the route code used to get a train to Hatfield, and the 0019 refers to how you set the APACU to get Blue Line announcements for a westbound trip from Cleveland to Hatfield. For a route code, it doesn’t matter if I’m out at the airport, leaving the Elmonica Yard, or anywhere else- if I’m directed to go to Hatfield Gov Center, my route code will be 99. Doesn’t matter where I’m starting from. The APACU, on the other hand, is based both on where you are and where you are going. It is location-dependent where you’re starting from in order to announce all of the stops, so each of those destinations to Hatfield has a different APACU value.

Eastbound Blue Line, BTC Pocket track

An operator can reprogram the APACU along with the route code if their train gets rerouted so that their announcements match the new route. The above picture, which is a little hard to see in the dark, shows the pocket track at Beaverton Transit Center (which is typically used only by Red Line trains) with a Gresham-bound Blue Line in it. I forget exactly what the problem was the night I took this picture but westbound trains needed to do turnbacks at BTC, so Blue Line trains headed west to Hillsboro were directed into this track instead of the westbound mainline so they could turn back east. Even though this train was headed for Hillsboro when it came into Sunset TC, the route code was changed to send the train into the pocket track at BTC, and once the operator got here, the APACU was set to have the stop announcements match the eastbound movement back to Gresham.

This train is not in service

The route code and APACU codes are two different systems. Because they function separately, this is what allows an out-of-service train to go wherever it needs but keep a “NOT IN SERVICE” message on the external signs. And no internal announcements either for out-of-service trains – I remember that had been a bit of a shock for me when I was in training and we took out-of-service trains on the mainline for the first time to learn where the platforms were and when to begin braking for them. I had assumed that I could just listen for the announcement of an upcoming platform to start braking since I had made the association that the announcements usually come around the time that the train begins slowing down for a platform approach, but nope, no announcements when your APACU is set “Not In Service”. Had to learn where everything was without that kind of help!

So how does it work?

No GPS involved – the announcements work by counting how many times the wheels turn between platforms. In the older cars, the counter resets each time the doors are opened, and APACU won’t advance forward if the doors don’t open at the current platform. However, the Type 4 announcements will still advance forward even if the doors don’t open at a platform.

In the event of running reverse traffic (e.g. east in the westbound track) the APACU can tell that you’re approaching a platform but it doesn’t know enough to tell you that the doors are going to open on the other side of the train, so in those cases the operator will have to make a PA announcement to manually correct the error. This is a very infrequent occurrence.

On routes that change color or go out of service, the scrolling of the external signs happens automatically. For example, if you’re on a Yellow or Green train headed south toward PSU, the signs will automatically start scrolling to Out of Service after you leave City Hall/SW Jefferson with no action required on the part of the operator. When they get into the turnaround at Jackson, they’ll set both the route code and APACU for where their train is scheduled to go next.

On the Type 4s, that square with a circle in it…

… theoretically should indicate that the train changes color (e.g. from a Red Line to a Blue Line at Gateway because it will go to Willow Creek or Hatfield, not terminate at Beaverton TC), but yes, sometimes a 4 will display that only on one of the LED boards or in a context that makes no sense:

Red square, nothing in the circle to… Expo?

Could be the result of a random error, from taking power under a section isolator, the phase of the moon, etc. I was joking about the phase of the moon part.  Mostly. The 4s will also sometimes display a self-test error on one or more of the LED signs.

The 2s and 3s will get their share of announcement errors as well. Sometimes the audio announcements will be fine but the readerboards will be stuck on a stop, or one of the exterior signs gets stuck. You can try resetting the APACU, but that doesn’t always work for everything. The good news is that it doesn’t affect how the train runs until a mechanic is able to fix it.

Sign stuck between two red signs… on a Yellow Line train

This will be a new platform opening Spring 2012