I forgot that Alternatives 4 and 5 (Bechtel's proposal) would use single-bore tunneling, and because the trains would be much shorter, so would the construction costs associated with the station boxes.
The idea of 3-car trains (initially), which would actually be shorter than our current 3-car LRT trains, has me a bit uneasy. Peak headways of 2.5 minutes is also nothing to write home about... other systems around the world deliver more frequent service (and longer trains to boot).
In the redacted technical proposal released last year (
https://www.dropbox.com/s/4ip41fut92...82%29.pdf?dl=0), Bechtel states:
• 24/7 operations will be possible, if necessary
• Peak frequencies would be 2.5 minutes, off-peak 5 minutes and 10 minutes (lame)
• "Ultimate capacity" is 27,200 pph per direction, with 4-car trains every 90 seconds
• 4-car trains would be 288-feet long, platforms 280-feet long (our LRT station platforms are 270-feet long for comparison)
I think it's not insignificant that Metro put the 6-car "legacy" option on the table. Per the Scoping Report, Alternatives 5 and 6 have the same amount of support.