Seattle's Alaskan Way Viaduct was recently torn down, three weeks before being replaced by the new tunnel. Many predicted that this would lead to traffic gridlock, but in fact the impact on commute times was modest. 

In the journal Transportation Research, Senior Research Scientist Hana Ševčíková and Professor Adrian Raftery predicted that commute times would not increase much if this was done, and the recent tear-down tested their prediction eight years later. 

Raftery was recently interviewed on KUOW Radio about their prediction. (See the last link on the web page). He discusses his traffic modeling and subsequent vindication.