For what it's worth, I briefly looked into why we don't construct more above-grade track. There's actually quite a lot in the outer boroughs of New York (and of course one such mostly-freight track was converted in the High Line). It's cheaper to upkeep, and actually possibly cheaper to buy (compared to cost of drilling), and of course gets built much faster. The problem is essentially noise. Light is also a concern but not quite as large.
I wonder if anyone is working on making these trains more silent. It seems hard but might be quite valuable.
The elevated portion of the expo line in LA is remarkably quiet. Imo it's far quieter than a highway or even an arterial road. The problem is concrete supports are a lot more expensive and take more time to build than cheap creaky squeaky steel girders that you see in chicago and nyc. Plus, somehow, people were still pissed as hell about that train in LA and managed to dilute the plan from being a fully grade separated line into a mixed grade mess, where it might take you 15 minutes to travel through certain 2 mile stretches (on a train capable of 75mph).
I wonder if anyone is working on making these trains more silent. It seems hard but might be quite valuable.