Portland MAX Signaling Primer

In the 1980's and 90's North America's light rail renaissance didn't just save money over traditional urban metro systems by embracing street running and low level boarding. At the time, the signaling standard for "heavy" metros involved full CTC and cab signaled ATC, which came with both high infrastructural and operational costs. However light rail systems got a pass to re-write the rule book and adopt signaling practices that hankered back to the low cost interurbans of old with single direction operation and limited use of interlockings. While I have previously covered two examples of these low cost signaling practices in Denver and Dallas, I recently had the chance to explore a third in Portland Oregon.

Beginning operations in 1988 and seeing significant expansion in the 90's and 2000's, Portland's MAX light rail has the typical mix of downtown street running and dedicated suburban rights of way with operating speeds up to 55mph. The signaling of choice is single direction 3-aspect Automatic Block signaling using US&S transit type signal heads. There is little formal distinction between interlocking and intermediate signals each signal is the same in having a line-prefixed number plate.

One quirk of the system is the setup of having an ABS exit signal at each station and another ABS signal between stations. When a station platform s within a block, the signal will at best display yellow Approach so there is a distinct rhythm of exiting a platform on a Clear then entering the next on Approach. Intermediate signals on the main line away from stations are often of the high mast variety with earlier installations using US&S N type mono-block heads.

A key feature of the MAX train control system is the use of fixed inductive Automatic Train Stop (ATS). Unlike some other systems, MAX actually includes a bit of overlap to get trains stopped before they hit something. This is made possible by an LRV's enhanced braking performance necessary to handle the challenges of street running. Apparently MAX also has a few ATS based speed control timers that function independently of fixed signals, but are indicated by wayside signs.

Interlockings are limited to major junctions, yards and a few select crossovers. These are supplemented by hand operated temporary block stations. As I said before, both ABS and Interlocking signals are largely the same except for the possibility for route indications on the interlocking signals. This can range from the use of a single lamp in the "call-on" position, or separate heads, each governing a specific route. The wayside signals are supplemented by switch position indicators of the US&S ES-20 variety.

When Urbex Meets Signaling

While there is a lot of crossover between the urban exploration (Urbex) community and the rail enthusiast community, the Ven diagram doesn't quite work the way you think it does as there is both the type of enthusiasm the individual is involves with (rail, urbex or both) and the type of things they explore.  When railfans explore rail stuff, they tend to put the resulting content in the rail bin, even if they are also into Urbex.  Qualified railfans know the jargon and historical details to properly label their content, rendering it searchable and discoverable. On the other hand, Urbex people who aren't railfans, can get into a lot of interesting rail places, yet have little idea of what they are looking at, therefore harming discovery.

Not so long ago I found some critical WINSLOW tower interior photos from 2003 on an urbex blog site that just hadn't happened to appear on casual google searches until recently. In the same vein, I also found a great exploration of the former PRR MG tower on the famous East Slope between the Horseshoe Curve and the summit at Gallitzin. I routinely search for new "interlocking tower" videos, but not "switch tower" because the genericness of the term returns a lot of bad results.  It was only after several years would YouTube searches include this video in my interlocking tower search due to the key words in the comments.

Despite their lack of historical context, the Urbex community can assist the railfan community by being willing to generally take more risks than railfans. In this example MG tower is known to see increased police patrols to the point where the risk of visiting is well known.  On the other hand, Urbex folk don't care about getting train photos and can put more effort into not being see in addition to just having more experience in not being seen. Therefore, while railfans steered clear of MG, this guy was able to made a comprehensive video documentation. Another popular urbex assist has been the Hoosac Tunnel in northwestern Massachusetts, which sees both explorers and ghost-hunters occasionally getting some footage of the searchlight signals inside.   

Anyway, the next time you are looking for some open source intelligence on some hard to access signaling artifact, try to use some urbex search terms. You might find something surprising.

New Signals at Portland Union Station

For the last year or more, Portland (Oregon) Union Station has been involved in a slow motion re-signaling project that will unfortunately zap the last active vestiges of VC Tower, which closed in 1996 as Oregon's last active interlocking station. 

Until labor dynamic forced a change in the early 2000's it was not uncommon for railroads to splice old interlocking hardware, like switches and signals, into new control logic. VC was one such example where the eastbound signals were left untouched. 

These included a short mast signal off of passenger track #1 with a mix of GRS type E and L&W modular lamps, a modernized GRS type MF triangular dwarf, (popular with UP in the 80's and 90's) off main track #4 and two vintage GRS type MD dwarfs on track #3 and #5 that likely date back to whenever VC tower changed over from semaphore signals. 

The replacement will be an obtrusive double cantilever mast for tracks 3, 4 and 5 and a likely modern type mast on track #1. 

The current two lamp dwarf signals appear to consist of a red lamp over a yellow lamp, which would provide for Y Approach, R/Y Diverging Approach and *R* Restricting, although was not able to observe actual operations. The new signals seem to bring Y/Y Approach Diverging to the table. 

The changes aren't limited to the east side of the terminal. For some time passenger tracks 1 through 4 have been un-signaled with the west end of of those tracks being reached via non-interlocked M23 powered switches. Based on bagged station track signals and a bagged through track mast it appears the west end will also be interlocked, including the presently hand throw station track #1.

This will hopefully cut a couple of minutes off the run time, with trains possibly able to make hotter stops, instead of creeping down the super long platforms. 

The End of Main Line Pneumatic Points

There's a lot of work taking place on the former PRR Northeast Corridor these days and unfortunately it appears that the era of main line pneumatic point machines might be nearing an end. The stock of pneumatic interlockings had been dwindling for years with LANDOVER near Washington, DC, GRUNDY in Bristol, PA and FAIR in Trenton being the two latest to see wholesale conversion to electric US&S M3 style machines. Prior to that both THORN and PAOLI interlockings on the Harrisburg Line saw their pneumatics go even while their interlocking towers remained open.

Currently, what had been some of the best preserved main line pneumatic interlocking plants, RIVER and POINT at the north end of Baltimore's Bayview yard, are in the midst of an electric conversion as their turnouts are being replaced as part of a general maintenance project. 

Unfortunately, due to their location, these two locations are difficult to photograph except from the rear of passing Amfleet equipped trains.

This will leave what is in my estimation only a single intact pneumatic main line  interlocking plant, HOLMES, at Homesburg Jct in Philadelphia. OVERBROOK interlocking, with its staffed tower, is still largely pneumatic, but had seen select turnouts replaced with M3's.

 

Of course a significant number of terminal plants will remain pneumatic for the foreseeable future and one could possibly count terminal adjacent interlockings like Metra's TOWER A-2 and SEPTA's 16TH ST as Main Line as well, however neither see the high speed movements currently present at RIVER, POINT and HOLMES. The challenge for documentation is capturing the movement and sounds of the switches as they throw. At HOLMES this is most easily covered when local freights enter and exit the Buttleton branch, but this could also be achieved when tracks are out of service east or west of the plant.  Of course the easiest way to engage with pneumatic point machines is to see them on rapid transit systems such as The PATH, NYC Subway and the SEPTA Broad Street Line.