Friday 15th March 1968

Construction started on the north tunnel of the Eisenhower Johnson Memorial Tunnel on Interstate 70 in Colorado, some 60 miles west of Denver, US. Located at an altitude of more than 11,000 feet, the project was an engineering marvel and became the world’s highest vehicular tunnel when it was completed in 1979. Four months after opening, one million vehicles had passed through the tunnel. The largest one day volume was over 50,000 vehicles, one million vehicles in a month is now commonplace. Because of this volume, the traffic is monitored, and sometimes traffic is held back until a queue has cleared from the tunnel for purposes of safety.