So, here's the scoop....
The reason why you're sitting there could be one of a number of different issues. These are all generalities, but they're the most common and likely ones.
- Your train is early. You have arrived at Union out of sequence, and so you get parked to wait for your turn.
-> They can't just put you on another platform track, maybe because another platform track is not open. Or one is, but would require routing you onto a track that may result in delays to a different train or trains.
- Your train is late. You have arrived at Union out of sequence, and so you get parked until the RTC can find a place & time to slot you in.
-> They can't just put you on another platform track, maybe because another platform track is not open. Or one is, but would require routing you onto a track that may result in delays to a different train or trains.
- The train ahead of you is late. You have arrived at Union on time and in sequence, but the train occupying the platform that you guys are headed to is in the way.
-> They can't just put you on another platform track, maybe because another platform track is not open. Or one is, but would require routing you onto a track that may result in delays to a different train or trains.
- Your train is on time. The train ahead of you is on time. The schedule is so padded that if you are on time you are forced to wait until the train ahead moves along.
-> Honestly, this is the most likely case.
There are certainly other possibilities - the RTC's are worked hard during rush hours, and there's absolutely been cases when trains have been delayed because they missed/forgot about it. Or there could be a work block occupying a track, and so all of the service - both revenue, and non-revenue deadheads - need to operate on one track less, meaning that trains need to get slotted in one-after-another. But these reasons are one-offs, and unlikely to happen on a daily basis. The ones above are more likely to be recurring.
One other thing - given the choice, it is easier for an RTC to further delay a single train than to make a maneuver that would minimize the delays to that single train but result in delays to multiple other trains. They follow a "grid" which tells them what train should be in what place and at what time - and if a train falls out of that sequence, the grid will take precedence.
Dan