Have there been studies done to investigate making U.S. 1 either a depressed roadway with alternative bridge crossings or a tunnel throughout the project corridor?

PennDOT and their design consultant engineer previously completed an initial high-level investigation into both a tunneling option and also a potential depressed roadway alternative with access (bridge) crossings. The initial investigations had the cost of tunneling in the range of $900M to $1.3B based on similar projects nationwide. The initial investigations into a depressed roadway (excluding capping with green space) were in the range of $300M to $400M. Additionally, future maintenance would also need to be taken into account, which is considerably higher for an underground facility when compared to a typical at-grade roadway.  Lastly, detailed studies/reports were not completed for either option to determine constructability/feasibility.