[M II A II R II K]

I take it that this idea works better if the freeway or railway is at a sunken level and maybe there are some ideal places to create some here.

L.A. is starting one.




http://hollywoodcentralpark.org/home

[video=vimeo;31980051]http://www.vimeo.com/31980051[/video]

 

[sixrings]

Allen expressway

 

[BurlOak]

The new border crossing at Windsor will have a bit of this. (couldn't find a great link)

http://www.mto.gov.on.ca/english/engineering/border/windsor/wep/index.shtml

 

[Markster]

L.A. is starting one.

Not quite "starting".
It's not really on the radar for anyone aside from the local councillor, and from what I hear he has a poor track record of follow-through.

Not to mention how hugely expensive such a project would be. Though, there could certainly be merit to doing small (affordable) sections at important locations.

 

[Woodbridge_Heights]

The central rail tracks. Another great reason for electrification.