I wonder what they have in mind for how stations will offload/onload capsules onto the loop. That will be heck of an engineering problem to solve - ultra high safety, pressurized environment, fast turnaround times...
My initial thought was they would have switches on the track like a normal train and capsules would veer off. But I bet they would come to a stop on there own and then get lifted vertically off the train and into a decompression area where they'd cue up.
This is addressed in the document. Essentially, each station is a terminus, so airlocks are transited at low speed. A turntable reorients trains for their next trip. The only switching required takes place entirely within the evacuated zone. (This is for when spurs are built to serve e.g. San Diego or Las Vegas.)
My initial thought was they would have switches on the track like a normal train and capsules would veer off. But I bet they would come to a stop on there own and then get lifted vertically off the train and into a decompression area where they'd cue up.