If you think that's big, check out the Katy Freeway:
• Video Link
Getting way off topic, but if those HOV/HOT lanes existed here in Canada they would be awesome with dedicated exits and such. They would also eliminate the inability to pass slower drivers.
Also if the major interchanges on the 401 were stacked like that it would make for a much more efficient highway, but at the cost of what is considered to be urban blight. 4 and 5 level interchanges can be seen from quite a distance, especially if none of it is below ground. (400/407ETR is a 4 level stack but one level is depressed.)