To date, most of what I’ve written about has been how things work under normal operating conditions because, well, that covers most of what people ask about since it’s what you encounter on a day-to-day basis (how fast do the trains go, what kind of signals do they use downtown, etc). But there are a lot of interesting things that go on outside of normal operations (e.g. manual blocks), and if you were riding the trains through the recent weekend maintenance work between Sunset and BTC or on the Yellow Line, you would’ve seen some unusual moves, wayside flags, and signal aspects.
If you missed it, it’s okay, other people went out and took pictures and are letting me use them, so thanks to them I’ve got some content for this post.
First off –
What was the maintenance work for, anyway?
As you may recall (and now that we’re heading into June, I expect this old entry to start getting more traffic if/when we get a heat wave), extreme heat conditions can adversely affect rail. In areas at risk for sun kink, which is a lateral slide in the rail caused by the rail buckling as it expands in the heat, slow orders (reductions in speed over a specified area) are issued.
The expansion joints prevent this buckling by having gaps in the rail that give room for the rail to expand, thus absorbing the stress and force of the heat expansion. In order to put these expansion joints in, parts of the alignment had to be shut down.
So what does that involve?
When a track is out of service, double red wayside flags will be used – one in between the rails, one immediately next to them (also seen at Sunset on Pdxrailtransit’s blog). You do not proceed past double red flags for any reason.
Double red flags will be preceded by yellow and red wayside flags like these. These indicate that a train will have to stop within 1000 feet. Here on Interstate, these were placed before the southbound platform at Lombard because trains were using the switches just north of the northbound platform to turn back.
This train has already turned back and is now heading south on Interstate. Those of you with sharp eyes may have noticed a familiar signal in the last two pictures, with an unfamiliar aspect:
Time lock switch refresher time! These summary switch indicators on Interstate inform operators of the state of the time lock switches. Under normal operating conditions, these display a lunar which tells operators that the switches are aligned normal and are locked. Once the padlock for the switch has been removed, the summary switch indicator will display a yellow X, as shown above. For this work, operators stopped trains just past the 427 A and 427B switches, went back to what had been the trailing cab of their train, and crossed over to the southbound track to continue service southbound. Because the padlocks were off so that supervisors could throw the switches to enable trains to make this move, this summary switch indicator for the 427 switches displayed a yellow X.
Time lock switches were also used on the west side for turnbacks, as shown here at Beaverton Transit Center (also at Sunset for trains to go back east – sorry, no pics of those):
This series of pictures shows an eastbound train approaching BTC via the pocket track, which is normally the end of the line for westbound Red Line trains. This train is going to head west from BTC out of this same track, this time switching over to the westbound main. If you’re not very familiar with the layout here, it may help to see the overhead view – even though it takes a while to get a train through time lock switches, there’s not really any alternative to doing turnbacks from this side, and the time lock switches are still much faster than requiring trains to run reverse (which would involve restricted speed, no signal protection, use of island circuits to cross gated intersections, etc).
Similar to the first picture of the double red flags on the Yellow Line where you can see supervisors ready to throw the switches once the timer counts down, Pdxrailtransit got some pictures of supervisors at BTC who were on hand to throw these switches – remember that time lock switches are manual switches, not power switches, so they can’t be thrown from the cab of the train. Someone on the ground needs to manually throw the switch, and while operators can do it when necessary, it’s faster to have someone else taking care of it in planned situations like these.
So sure, some passengers were not happy with the additional travel delays, but for the people who like seeing some of the more unusual operations of the system, there were some nice examples of that over the last few weeks. Silver lining, right? And the expansion joints will make those areas safer in hot weather, so really this benefits everyone.