How many trains will be operating at once?
Until recently, I've been thinking only four trains at a time during rush hour (two trains in each direction an hour).
I've seen drawings where platforms look a little too short to accommodate two trains coupled together. However, I can't find documents showing platform lengths anymore.
There is a lot of space between train doors and the end of each train, so platforms may not need to be the full length of two trains.
Now, I'm thinking 8 trains at a time during rush hour. Seems like a waste to order 8 trains if you only need 4 or 5 trains at a time.
The TexRail Flirts will be 266 feet long, the platform lengths should be a minimum of 266 feet long.
These trains will require refueling during the day if ran continuously. What they will do is pull the trains after the morning peak, place other trains on during the day and pull them before the afternoon peak, place the earlier trains on for the afternoon peak, etc. That way they don't run up too many miles. Then they can refuel all of them overnight. There will be one additional train as a spare in case one breaks down and needs to be pulled for an entire day for corrective maintenance so the train schedules aren't affected.
Eight trains in their equipment roster isn't too many.
I'm going to have to dig through the FEIS to find the exact station platform lengths.
The maximum length of any station platform from the beginning was 450 feet, but they always planned to build smaller (anywhere from 250-300 feet) and leave room for expansion later. Initial planning assumed 8 inches above the top of the rail for the platform height, but that was always subject to change depending upon the vehicle bought. Since they have bought the vehicles, the platform height will be 2 feet above the top of the rail (24 inches). The standard low floor height of a Stadler Flirt is 22 inches, so the platform will be about 2 inches higher than the train's floor at the door. The only platform length I could find in the Appendix E drawings of the FEIS was for the DFW Station, which will be 318 feet long initially, with room to expand to 450 feet later.
Even at 450 feet, the platforms will be too short to fit two 4 car Flirts. Therefore I think you are correct stating the platforms will be too short to run two existing 4 car Flirts. From what I can gather over the web, 6 car DMU Flirts is a possibly in the future. Maybe adding 2 more cars to the existing fleet or by buying brand new 6 car Flirts will be the expansion method chosen. I'm pretty sure a 6 car DMU Flirt would fit alongside a 450 feet long platform.
Here's how I determined that.
A regular (EMU) 4 car Flirt is 246 feet long
A regular (EMU) 6 car Flirt is 349 feet long
Math determining length of the DMU van.
266 - 246 = 20 feet
Therefore, adding 20 feet to 349 feet = 369 feet
If a 6 car DMU Flirt would be underpowered, adding a second DMU van and another 20 feet to the train should solve that problem, the train would be 389 feet long in that case. Still far short of the 450 feet reserved for platform length in their plans.