In reply to Bill Lindeke.

I really like the look of this Columbus OH example I just came across. It'd be far cheaper than a large linear park option. You just do it at a few key bridge crossings, like Nicollet...

http://featuresblogs.chicagotribune.com/theskyline/2011/10/ohio-highway-cap-at-forefront-of-urban-design-trend-retail-complex-atop-columbus-expressway-offers-m.html