Imagine this in NYC or any other big city.
(https://lh3.googleusercontent.com/-PVbz1qxxRyM/UQKIFsNQOmI/AAAAAAADbNE/NsFv3w6FPbQ/s666/523703_352871858115858_1479421517_n.jpg)
Hanshin Expressway in Japan
Yes, Osaka to be exact (https://maps.google.com/?ll=34.6981,135.489573&spn=0.001354,0.00327&t=h&z=19)
http://en.wikipedia.org/wiki/Gate_Tower_Building
For better or for worse, we have eminent domain here. But you don't have to imagine; walk NYC's High Line, an old freight rail line:
http://maps.google.com/maps?hl=en&ll=40.742124,-74.007736&spn=0.003707,0.008256&gl=us&t=m&z=18&layer=c&cbll=40.742208,-74.007713&panoid=it6dmhdqQHenWgDaaLzLMQ&cbp=12,191.76,,0,-2.75
Interesting in that that interchange ramp 'floats' through that building, the two do not touch.
Mike