^^^
Yeah, the intersection at Main & 4th is capacity constrained, but that's because the junction was designed and built on the cheap, and it seriously needs to be upgraded.
This section of TRAX, between the Stadium and Main Street was rushed to completion before the 2002 Olympics, and opened less than 3 months before then (in December of 2001). The junction at Main and 4th was designed to be built FAST, so they took some shortcuts. The most obvious short cut was that there is only one motor for two switches, meaning that if you want to align a switch from the northbound position to the eastbound position, both the northbound and southbound switches are thrown together. This alone reduces the available capacity by half; imagine you've got a train about to turn from north to east (Main to 4th), from west to north (4th to main) and then one going straight south on Main. None of these movements interfere with one another, yet with the way the switch is built, it is IMPOSSIBLE for all three movements to happen all at once, because all the switches would be thrown in the wrong directions. Each movement would need to happen one at a time.
Then there is also the outdated signaling systems, the slow motors, etc. The switch is definitely going to need to be rebuilt one day, and the designers are probably pretty impressed that it has lasted this long. One of the reasons they justified doing this project on the cheap is that they thought that junction would be totally rebuilt into a 4-way 'grand union' intersection once work began on the airport line, which was thought at the time to be an extension of the University Line (FrontRunner came along and threw a wrench into the TRAX original master plan).
UTA is only just now fixing other 'done on the cheap before the Olympics' quirks along the downtown section; they only just got the two switches on 7th south to work automatically from TRAX HQ, rather than have a dude drive over in a truck and throw them by hand:
http://www.masstransitmag.com/press_...o-improve-trax
And if I were to speculate as to why they haven't fixed 4th and Main on their own, it is because they got a grant a while back ($2 million) to start running the BLACK LINE. They claimed they needed $4 million more, but the city and state didn't give them any money, and the federal government sure won't. Why does it take $6 million to start running TRAX trains you already own on track that already exists? Because there is a junction that needs to be upgraded, and UTA wants some one else to pay for that (or at least help pay for it). And so we wait for the BLACK line, instead of riding it.
My point is that when they say 'it is capacity constrained,' think 'my 8 megabyte flash drive has no more space.' The correct answer is to upgrade the flash drive, not be content with what we've got.
I personally won't be satisfied until there are
SIX TRAX lines converging on a grand-union junction on Main & 4th, each operating at 10 minute headways. The Red, Blue, and Green lines remain as they are, then add in the Black line turning from 4th to Main towards the Airport. Add in a TRAX circulator that makes a loop from Main to Salt Lake Central via a 4th South line, and then extend the Blue line from Salt Lake Central station along 4th south as well, all the way up to the University. (The University line already has the high-block platforms for ADA able to handle the old Classic cars used on the Blue line, so why not?)
If each line runs at a 10 minute frequency, that means a train arrives at the intersection every 50 seconds. Compare this to the current schedule of a train every 150 seconds, and you'll see its only 3x more than what our current outdated switch can handle. It's totally doable, and the only track that needs to be built is the extension along 4th south to Salt Lake Central Station, about 1 mile. I honestly can't see why this sort of thing isn't even in the planning phases; it is more low hanging fruit, it is like putting the last piece of a puzzle in place. 1 last mile of track downtown and the operational potentials go exponential.
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