I knew this project was going to turn into a massive Clusterf^&k the first time I saw the announcement. I still think the entire Great Hall project to put most of the space post-security is incredibly ill-conceived and I hate that I might ultimately be proven right. The only real benefit would be to straighten out the security checkpoints and increase passenger throughput but I don't see how forcing everyone to schlep to the north end of Level 6 is going to make that process any more efficient than what currently exists.
Maybe it's just me but in some of the comments here it seems like there's confusion with the various trains at DIA. As far as my memory goes (back to 1995) the automated people mover between the concourses has always run with 4-car trains. If anyone remembers differently then by all means correct me but I recall that capacity was adjusted through frequency, not by adding/subtracting cars.
RTD's commuter rail service between DIA and Denver started running in Spring 2016 with 2-car trains. Those were expanded to 4-car trains in January of this year (same schedule and frequency).
There are three main reasons that the Great Hall project was necessary, they are:
1. Most of the mechanical systems are more than twenty five years old at this point and need to be repaired or replaced, the airport looked at an option; that included upgrading every system in its current location and the cost was 250+ million, while making the terminal look nice, it would not do much to increase capacity. The terminal was built for 50 million pax a year, this year the airport will have close to 67 million.
2. From point 1, they needed to add capacity, the renovation will add 30 million more to the capacity, with the new layout there will be a similar number of ticket counters and more TSA lanes.
3. Many experts have said the current layout with security lines being surrounded by a mezzanine is incredibly insecure for active shooters situation, unfortunately we have to plan for situations like that now and that is the main reason for security to move to level 6.
The trains will begin receiving additional cars next year, this will allow them to increase the frequency and replace the original sets of cars the airport opened with. Every station is capable of handling 6 cars trains, with minor modifications, there is no timeline for increasing the length at the moment just the frequency.