Side note, the one of the main area of research at the University of Washington's structural engineering department is speeding up construction and repair of bridges. It largely involves using pre-cast concrete as much as possible. The hard part is making the connections ductile*. For what its worth, quad is right, pre-cast makes repair and replacement a lot easier. State DOTs have also pretty much standardized their overpasses to more or less be interchangeable. That helps, as quad notes, it means any precasters in the state will likely have the molds sitting around.
*Ductile means able to absorb a lot of energy prior to total failure so it fails slowly and folks have enough time to get way from the thing before it collapses.
