I was posting these nuggets to twitter, so I might as well bring them over here in full. Below is some data I've dug up on the Cheonggye Freeway in Seoul, SK that was removed and the buried stream was restored:
Removed 8.5 miles, which moved 1.5 million cars per day.
Cost: $33 million per mile to remove and restore stream.
Within ten years of the initial elevated highway construction, Seoul CBD lost 40,000 residents and 80,000 jobs.
Housing value increased 30%
Number of vehicles in the area per day dropped 43%
Summer temperatures: 8 degrees cooler
Air quality: 21% less tiny particulate matter called PM10
NO2 dropped 20%
BETX pollutants dropped 25% overall and 65% in certain areas
125,000 visitors come to the park each weekend day. 53,000 during weekdays
113,000 new jobs have been created along the corridor
long term economic benefits estimated between $8.5 and 25 billion