an abandoned short spur of the mainline heading north. A pair of trumpet interchanges were built to connect the Northeast Extension and I-81. In 1974, the roadway was designated PA 9. When it first opened, traffic on the Northeast Extension of the Pennsylvania Turnpike was light. By the 1970s, traffic along the roadway increased with the completion of the connecting I-80 and the rising popularity of the Pocono Mountains as a vacation destination. As a result, the two-lane Lehigh Tunnel faced serious congestion. Plans were made to either bypass the tunnel or add a second tube. The turnpike commission decided it would build a second tunnel as the cost was lower than building a bypass. In 1988, a $37-million (equivalent to $ in ) contract was awarded to build the second tube. Groundbreaking for the tunnel took place on February 14, 1989, with Governor Robert P. Casey in attendance. Excavation of the new tunnel began in July of that year. Construction of the second tube utilized the New Austrian tunneling method, which reduced the cost of the tunnel by $5 million to $6 million (equivalent to $ to $ in ). It was the first tunnel in the US to use this construction method. The second tube at Lehigh Tunnel opened on November 22, 1991, with Governor Casey in attendance leading a line of antique cars. Construction of the tunnel cost $45 million (equivalent to $ in ). The new tube is used for southbound traffic while the original tube carries northbound traffic. The newer tunnel is wider, higher, and brighter than the original. On February 1, 1995, the Keyser Avenue interchange near Scranton was slated to open at a cost of $22.4 million (equivalent to $ in ). Construction of this interchange also involved constructing a new mainline flat-rate toll barrier near the new interchange. On November 1, 1996, the Northeast Extension was added to the Interstate Highway System as a northern extension of I-476, replacing the PA 9 designation along the road. The addition of the second tube at the Lehigh Tunnel along with new guardrails and line striping was necessary for the toll road to become an Interstate. It was hoped that the Interstate designation would bring economic development and tourism to the areas served by the roadway. This extension resulted in I-476 surpassing the I-495 in Massachusetts as the longest auxiliary Interstate Highway, though it could