Since that date there have been no serious proposals to duplicate the existing tunnel, although cost estimates for such work were at $40 million in the mid-1980s. Traffic lights have been installed at the end of the city approach to the tunnel to ease congestion and improve safety at the Basin Reserve roundabout. Mount Victoria Tunnel became part of State Highway 1 in 1997 when Transit New Zealand designated the road from Wellington Airport to the Basin Reserve a State Highway. The NZ Transport Agency has no plans in the next ten years to duplicate the tunnel, but plans to investigate work to upgrade the city approaches around the Basin Reserve, including a possible flyover to Buckle Street, to reduce congestion at the city end of the tunnel and around the Basin Reserve. A study is currently underway (The Ngauranga to Airport Study) investigating long-term transport options for the route. The study indicates that a new tunnel would cost around (NZ)$170 million.