A while back, Dan B emailed this question about SkyTrain, and I thought I’d share the answer with everyone. (Dan B will surely notice this email was sent a LONG while back… so this is better late than never :)

I have a question about how SkyTrain works. I was riding the SkyTrain this morning from Broadway to Edmonds at about 8am . When we approached Edmonds, there was an announcement that the train was going to prematurely terminate there and that passengers continuing to King George would be accommodated by another train that wasn’t far behind. The train I was on stopped and had a longer dwell time than other trains normally have at Edmonds. Afterwards, it left and another train followed about 30 seconds later.

What was the purpose of doing that? Were they going to turn the train to provide additional capacity to the downtown core? Were they taking the train out of service and preparing to take it into the yard? Were they going to deadhead it to Broadway to provide additional capacity for that heavily-travelled segment?

Also, when I look out the window at work, I see other trains stopping at Edmonds for longer than usual times. Usually, another train has to stop behind them just outside the station. Is this because they are taking some of the trains out of service and returning them to the yard once rush hour is over? Do they break-apart the Mark II consists so that they only run with a single trainset?

Here’s the answer from Ian Graham, operations manager at SkyTrain (and the man behind the SkyTrain chime!)

During weekday morning commuter hours, SkyTrain operates 57 trains in service, representing more than 92% of the entire fleet, and the maximum we can sustain day-in, day-out, while keeping up with our active preventive maintenance program.

For mid-day we drop down by 21 trains to 36, which keeps a 6-minute frequency both to Surrey and on the Millennium Line, with a 3-minute combined service between Columbia and Waterfront. A few trains will be taken out of service at Waterfront, King George, and VCC-Clark, where they can be stored nearby in short sections of track out of the way of mainline train operation.

In addition, an average of about a dozen trains are taken out of service in the eastbound direction at Edmonds, which is close to our storage yard and operations centre, allowing them to be brought in for daytime storage (because we have only limited space on the mainline), or mid-day maintenance.

By keeping some trains in service eastbound from Waterfront, we keep more options open for the large loads that transfer from SeaBus and West Coast Express. While most of these patrons are only travelling a short distance within the downtown peninsula, we have an increasing number of passengers travelling beyond to Broadway, Joyce, Metrotown, and Edmonds. The trains have to get there anyway, so we have chosen in recent years to keep them in service, offering additional convenience to passengers in these areas.

However, it is unproductive to run them all the way to King George (the “non-peak” direction), and then “deadhead” them back to the yard without passengers. The reduction at Edmonds offers the best of both worlds –service and efficiency.

By the time we start taking trains out of service at Edmonds, usually around 8:55am, it is too late for them to be productive westbound back to downtown Vancouver. Any time that a train is taken out of service, our staff (SkyTrain Attendants) have to ensure that it is completely empty (we don’t want to take a “sleeper” into the yard). That takes a bit of time, so the train may be at the platform for up to a minute or so, and as a result, the train immediately behind may get held up outside the station for a short time – usually less than a minute.

At present, our mid-day service level is based around the operation of “short” trains (either 4-car Mark I’s, or 2-car Mark II’s), so we generally store the longer trains mid-day until afternoon rush hour. They will not normally be uncoupled during weekdays, although they will generally be returned to the 2-car length for weekends, so we can provide frequent, convenient service at the most efficient operating cost.

All right — if there’s follow-up questions, just be aware that I may be a while in getting back to you, as I have to pass questions on to SkyTrain, and Ian himself is a very busy man. (In the meantime, knowledgeable readers can feel free to pitch in with answers if they have them!)