Loud and sometimes vibration-inducing. But this seems potentially feasible to mitigate through sound insulation (both on the train and on the buildings; frankly, our buildings should have a lot more sound isolation than they do).
https://news.ycombinator.com/item?id=39401709 mentions newer elevated trains generating less noise, by designing for that requirement.
> they bathe streets/sidewalks/buildings in permanent shade
And permanent rain-cover. Seems like it'd often be a feature for many, though a bug for others.
The set back from the bridge to my building is about 5-10x as far from my window as an elevated train line running on an avenue would be.
I have new windows, plus a second set of quiet windows installed within the windows. Essentially quadruple pane windows. It makes them unusable for ventilation. Plus I have sound deadening curtains, sound dampeners on walls, etc.
Believe me, it is loud. There is no mitigation you can do to make it not noticeable. You can only make it tolerable. The cost to get it to that level is not insignificant.
Look at what they've achieved with this in Hong Kong. Plus the lines and stations basically pay for themselves due to revenues from residential property.
It's not apples to apples (light rail + heavy), but from experience the elevated parts of LA's Expo Line are a lot quieter than the Chicago L.
1. Elevated rail
2. Trenches with no cover
A series of campaigners in areas with higher property values wanted the trenches for “privacy” reasons and in the end many of them got them but the elevated rail receiving citizens got bike paths, basketball courts, car parks, improved walkability, generally more public space.
Having experienced the two, the elevated rail is far better.
The totally new line they are building though will be a TBM.