A visit to Seoul shows that it does not always take a natural disaster to remove an urban freeway. For centuries, the Cheonggyecheon (roughly "clear stream"), a tributary of the Han River, was a vital, though problematic, artery. Its name belied the fact that it was often polluted. (It had to be dredged for waste removal in 1760, for example.) By the 1950s, it was ringed with shantytowns and represented not only a health hazard but an embarrassment for a society bent on rapid modernization. Rather than being cleaned up, the stream was largely concreted, turned into a surface street; in 1971, work on the elevated, four-lane, 3.2 mile-long Cheonggye Freeway was completed. (One thing to keep in mind in wondering how cities could cover up or block rivers and waterfronts in their highway plans is that many of those places had lapsed into degraded eyesores; as Mia Birk notes in her book Joyride, the fact that Portland's Willamette River was a "toxic stew" in the 1950s almost certainly influenced the decision to place an elevated freeway along its banks.)
But, decades later, it became clear that Seoul had essentially traded a choked, polluted stream for a choked, polluted stream of concrete. In the 1990s, city traffic was increasing as much as 5 percent yearly. In 2002, Seoul Mayor Lee Myung Bak (later the country's president) began ripping down—at a cost whose estimates range from $380 million to over $900 million—the very highway he had, as a former Hyundai engineer, helped build.
While feasibility planners like to talk about strange traffic dynamics like the "Braess Paradox"—as one explained, "by taking away space in an urban area you can actually increase the flow of traffic, and, by implication, by adding extra capacity to a road network you can reduce overall performance"—Seoul's team wasn't leaving things to mathematical chance. Accompanying the teardown was a vigorous "demand management" campaign. They instituted a Bus Rapid Transit system (subway expansion was deemed too costly) along the former highway route. The stick of increased tolls and parking charges to discourage driving was mixed with the carrot of reduced tolls for those who participated in weekly, voluntary "No Driving Days." (One study found a 1.3 percent reduction in vehicle use with these policies in place, a small yet significant figure, the authors argued, considering the program was voluntary and affected more than 2 million vehicles.)
In a revision of "Big Yellow Taxi," Bak tore down the parking lot and put in paradise: A 1,000-acre-plus linear urban park dotted with bridges, artwork, birdsong, places to sit—and increased property values and lower temperatures. In a curious but poignant touch, a series of concrete support structures for the old elevated highway have been left in place, now looking rather like abstract human figures, holding their arms outstretched to the now open sky.