At Freakenomics, there is an article about removing urban highways and how that actually speeds up local travel times. They discuss the Cheonggyecheon in Seoul (and link to this article specifically about the river).
From Freakenomics (the paragraph contains links that can be found at the original article):
Strange how the traditional laws of supply and demand go out the window when it comes to traffic. Studies over the last decade (like thisone, this one, and this one; plus the bookSuburban Nation) have pretty much dismantled the theory that more roads equal less traffic congestion. It turns out that the opposite is often true: building more and wider highways can increase traffic congestion. If only people like Robert Moses and Le Corbusier had known this before their grand urban plans left our cities clogged with traffic, and carved up by ugly, value-destroying highways.
I also like the approach taken in New York where an elevated road was converted into parkland. The High line Park:
The black steel columns that once supported abandoned train tracks now hold up an elevated park—part promenade, part town square, part botanical garden. The southern third, which begins at Gansevoort Street and extends to West 20th Street, crossing Tenth Avenue along the way, opened in the summer of 2009. This spring a second section will open, extending the park ten more blocks, roughly a half mile, to 30th Street. Eventually, supporters hope, the park will cover the rest of the High Line.
Walking on the High Line is unlike any other experience in New York. You float about 25 feet above the ground, at once connected to street life and far away from it. You can sit surrounded by carefully tended plantings and take in the sun and the Hudson River views, or you can walk the line as it slices between old buildings and past striking new ones. I have walked the High Line dozens of times, and its vantage point, different from that of any street, sidewalk, or park, never ceases to surprise and delight. Not the least of the remarkable things about the High Line is the way, without streets to cross or traffic lights to wait for, ten blocks pass as quickly as two.
I wonder if there is a bike path up there…