Question: What are those signs by the train platforms with things like “Main 1” or “A-3 Central”?

Those are reminders to operators to switch to the correct radio channel for the area they are in. The primary method of communication on MAX is over the open-air radio. Operators, Controllers, supervisors, field maintenance workers, etc all use the radio, and since the area serviced by MAX is so large, radio coverage is broken down into channels for each section – since an operator who is only doing the Yellow and Green lines doesn’t need to know about track work done by Orenco, for example.

Radio history

Originally there was one channel for mainline operations (Main 1), used from Gresham to CBD (Central Business District, aka downtown).  When the west side alignment opened in 1997, Main 2 was added and was the channel used from downtown to Hillsboro.

When the Yellow Line opened in 2004, Main 3 was added, and it split the way the channels had previously been assigned, geographically speaking.  The following four pictures were taken in fall of 2008, after the Yellow Line opened but before the Green Line did.

Main 1NE 7th Ave platform, looking east – eastbound trains would switch to the east side radio channel here from the CBD channel

Main 3 from 7thNE 7th Ave platform, looking west- westbound trains would switch to the CBD radio channel here coming from the eastside channel

Main 2PGE Park, Westbound – Trains would switch from the CBD channel 3 to the westside channel 2 here

Main 3 PGEPGE Park, Eastbound – Trains switch from westside channel 2 to CBD channel 3

But then the Green Line opened, adding north-south trains downtown as well as a stretch of alignment to Clackamas Town Center,  so the setup of radio channels had to be changed again.

Radio today (by which I mean spring of 2010)

Those old Main 1 through Main 3 signs are no longer used. Currently there are four channels that are most commonly used for mainline operations (there are also separate channels for the yards and other less-frequently used channels for other purposes).

Map of radio channelsThe 4 channels used on the mainline today (ignore the Streetcar on the map since it doesn’t use the radio that the MAX trains do, neither does WES which has been removed from the map).  Click for larger version.

A-5 PGEPGE Park, westbound platform

In green on the above map, A-5 “West”, from Hatfield Government Center to PGE Park.


In red on the map, bordered by PGE Park on the west, Oldtown/Chinatown on the east, and Union Station on the north, A-4 “CBD”

A-3 82nd Ave

A-3 Oldtown/ChinatownA-3 Union Station

In yellow on the map, bordered by Oldtown/Chinatown on the west, Union Station on the south, and NE 82nd Ave on the east, A-3 “Central”

A-2 82ndNE 82nd Ave eastbound platform

And finally, in blue on the map bordered by NE 82nd Ave on the west is A-2 “East”

Edited, fall 2010 – the temporary signs have been replaced. I haven’t gotten pictures of all of them. The geographic boundaries haven’t changed, just the style of the signs.

Tuning in

Because the broadcasts over the radio are open, anyone with a scanner can listen in.  I don’t have a scanner and so I don’t know how to set one up to follow rail communications, but you can use an online scanner to get an idea of what it’s like.  I’ve heard TriMet rail transmissions over OregonLive’s police scanner, so if you’re curious you can use that as a starting point.  However, since that scanner follows everything, in addition to rail you’ll also hear police, fire, & EMS broadcasts, as well as airport parking shuttles and probably some other things that I can’t identify.  I don’t know of any other free/easy way for the public to listen to radio broadcasts if that’s the sort of thing they’re interested in.

And one last thing…

This is a radio, not a phoneCeci n’est pas un phone

In the cabs, the radio handset looks like a phone.  It is not a phone.  If you see a train operator using this, they are not on the phone.  They are using the radio, which they are required to do, not using a phone while operating which is illegal.


5 responses to “Radio

  1. Pingback: Tweets that mention trimet #lightrail radio channels --

  2. nope not gonna do it

    Early history: 1986 to about 1993-1994: MAX operated on a UHF radio frequency (similar to the way the buses currently do) on the mainline (it was channel one on the train radios) and a simplex UHF frequency for the Ruby Junction yard channel – on the same channel pair that was used for the MOSCAD signalling from the fare and substation equipment. [Way back before the “modern” central control room, the substation feeder breakers and fare equipment alarms were monitored by radio instead of fiber optic networking.]

    In 1993 with the looming Westside LRT project, it became apparent that a single channel was not going to be sufficient. Unfortunately, there were no radio channels for expansion of TriMet’s UHF radio system to accomodate the anticipated growth. The City of Portland had just engineered and put into service a new 800MHz trunked radio network and welcomed TriMet with open arms (along with a $350,000 per year check to pay for system access and maintenance). “Main 1” (now “East”) was linked to the old UHF radio system while the transition was made in revenue and non-revenue vehicles. Main 2, Main 3, the yard channels, and all the rest, were just there as “placeholders” (actually, the WSLRT engineering and construction crews used them to coordinate their activities), and the controllers would answer trains on either ‘Main 1’ or the (simplex) yard channel – wherever the train called them from. In about 1996 or 1997, the first iteration of the control room was opened (prior to this, it was literally a closet on the third floor), and the controllers had direct access to the 800MHz system on the radio consoles (which up to this point, with a single controller managing the entire 15 mile alignment) had been done with a boom microphone and a loudspeaker attached to a base station radio – very similar to those that were installed on the T1lrvs up until a few months ago. All of a sudden the world was opened up and those other channels became active. Initially, Main 2 was used for pre-startup coordination of trains, and was managed out of Elmonica station with a dedicated controller. That controller was also responsible for work assignments much the way the station agents are today. When the Westside opened, they kept the work assignment job at Elmonica, but moved it to Main 3, while Main 2 was used to coordinate west side train movement (from Ruby Junction). When Interstate opened up and the decision was made to split the airs 3 ways instead of 2, another decision had to be made: where to put the “station agent channel”.

    Enter the rebanding project, which required replacing a vast majority of the train radios. We had the opportunity to reprogram the radios and make their operation more logical and name the channels more descriptively. (If it hadn’t been for the rebanding project, that would have cost TriMet about $30,000 in fees to the City).

    Now, we’re on the verge of returning to three mainline channels. But for all intents and purposes, the operators and field personnel won’t notice.

    Anyone that’s really interested can find all the pertinent information here.

  3. nope not gonna do it

    Oh… double secret probation bonus points for this one… the Streetcar is in fact on the same radio system (and accessible to anyone with a TriMet radio). It does, however, use different talkgroups.

  4. Old UHF freq of 452.325MHz for the main and 452.875MHz for the yard, both on a repeater licensed to KNCA959. I listened to it so long that I remember to this day the automatic station ID come up every 15 minutes, -.- -. -.-. .- —-. ….. —-. The simplex ‘op-op’ frequency that the operators used to talk short distances between each other using the old MX300 handhelds was 452.75MHz.

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