The Transport Agency is proposing an ambitious plan to either widen the Homer Tunnel or build another one beside it.
Nearly half a million cars, buses and campervans use the tunnel in Fiordland National Park each year.
In 2008, 17 tourists were lucky to survive after their bus caught fire inside the tunnel, the third such incident since 2002.
Transport Agency's Otago Southland State Highway manager Niclas Johansson says safety is prompting the investigation of several proposals.
Destination Fiordland manager Lisa Sadler says her organisation is backing the Transport Agency plans because of the importance of the Milford Road to the country's tourist economy.
