The question is already in the title, but I guess some context might be interesting:
I'm living in Munich (Germany). It is the area in Germany which is probably most expensive to live. Even the surrounding area is way more expensive. Building higher is only partially possible due to construction regulations (e.g. in the center nothing is allowed to be higher than the Frauenkirche; roughly 100m).
Most desired are the areas close to S-train stations, especially close to the ones that are highly frequented (I'd guess about one train every 2 minutes or so).
Almost at the center, there are buildings next to the train tracks. For example the Munich Google office. However, I have never seen buildings over the tracks (except for bridges). And the tracks cover a lot of space which is super central. To give you an impression, look at the screenshot below:
- North of the tracks, east of the yellow-colored bridge, you can see the Google office. the building isn't huge, but it's not small either.
- The big building in the top of the screenshot is Paketposthalle. It covers an area of 20.000 m².
- We're talking about 2200 EUR/m² to 4200 EUR/m² (source)
For this reason, I wonder why I haven't seen any buildings directly over train tracks. Is insulation against the noise the problem? Is safety a problem, e.g. if a train derails? Is it the vibrations that might damage the house? Building safety exits? Is there not enough area below where one could build the support structures for the building?
There are way more expensive areas around the world than Munich. I guess Hong Kong / Tokyo / Shanghai might be one extreme example. Do they have buildings over train tracks? I'm not talking about underground ... but thinking about it, I'm not quite sure if there would be a difference if the city grows over the train tracks.