The completion of the Big Dig is ‘tantalizingly close,’ according to Project Director of the Massachusetts Turnpike Authority Michael Lewis. Though officials declined to commit to an exact date for the opening of the Interstate 90 extension, they said the project is on track for its Dec. 20 deadline.

The connection between the Massachusetts Turnpike and the Ted Williams Tunnel is also 99 percent complete, officials said at a monthly progress meeting last week.

The MTA said it aims to complete the safety-tested extension of I-90 by Dec. 20. The extension will connect the Mass Pike, which currently ends in downtown Boston, with the Ted Williams Tunnel. The connection will funnel motorists underneath Boston Harbor to Logan Airport and Route 1A.

‘If you’re coming from Framingham to the airport, you’ll be able to go home the same way you came, the same night and you won’t get confused,’ Lewis said.

The I-90 extension is a key component of the Central Artery/Tunnel Project, which began construction in 1991. The project is designed to replace the existing crowded Central Artery system with a higher-capacity underground expressway. Once the new expressway is fully operational, the old system will be demolished and the area will be used for public open space.

Only a small amount of unfinished business remains, according to Lewis.

‘On all the construction, we are 98 to 99 percent complete,’ he said.

According to MTA officials, the only remaining tasks include the completion of safety testing. The Integrated Project Control System is 90 percent installed, but only a quarter of the equipment has been safety tested, they said.

The MTA stands firm that safety takes priority over any deadline, according to Lewis.

‘Each item needs to be individually tested and this is why we’re not picking a date,’ said Lewis.

MTA officials said the organization wants the public to be aware of the project’s progress as the deadline approaches. In an effort to increase awareness, MTA representatives will hold a media briefing every Wednesday afternoon at the Big Dig headquarters in the weeks leading up to the deadline.