 State Transportation Secretary Frederick P. Salvucci, aware of the issues surrounding the elevated roadway, proposed a plan conceived in the early 1970s by the Boston Transportation Planning Review to replace the rusting elevated six-lane Central Artery with a new, more efficient underground roadway.This plan was merged with a long-standing proposal to build a third harbor tunnel to alleviate congestion in the Sumner and Callahan tunnels to East Boston; the new plan became known as the Central Artery/Tunnel Project or the "Big Dig".These new roadways were built during a twelve-year period from 1994 to early 2006.