The USA doesn't often build automated light metros, so it's necessary to take stock of what works (platform-screen doors, construction planning, off-street viaducts that dodge traffic outright) and what doesn't (cost of construction in VHCOL area).

No doubt, there are probably many other things that have gone wrong in the project, but unless the USA starts building more, it'll never learn from those mistakes.

Case in point: the original US Interstate freeway standards used to specify that median barriers were optional if the median was wider than 30 ft (~9 meters). But later research showed than even 45 ft of median could still allow a vehicle to cross-over into oncoming traffic. The standard is now 60 ft, with old freeways were retrofitted with cable barriers to gently slow a wayward vehicle.