on november 1, 1996, the northeast extension was added to the interstate highway system as an 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.