[maxerickson]

The national highway system had unintended positive economic consequences. I guess it might fail the complexity test.

(I'll concede that it depends on what you want to measure, but it's hard to argue that cheap trucking has only been a negative)

[malyk]

It also had plenty of unintended negative consequences. See suburban sprawl, oil dependency, the health impacts of commuting, and a ton of other negative impacts.