Repairs were already under way at the interchange, where work had begun in January to rebuild three structures parallel to the originals. Weight restrictions had been in place since August but overweight lorries had continued to ignore the limits despited increased law enforcement, said Wisconsin Department of Transportation.

Data from 2005 showed Zoo Interchange to be the busiest freeway interchange in the state, carrying on average more than 324,000 vehicles a day in 2005.

The new bridges are an interim measure and a corridor study will recommend a long-term solution.