Thanks to the newer Ted Williams tunnel connecting points south from I-93 directly to East Boston, traffic coming north on the expressway will not really have to do anything differently. However, the expressway between the Ted Williams and the Braintree split is already known to be an insufficient piece of infrastructure plagued at all hours of the day with snarls of traffic. And while this traffic may not necessarily increase due to the construction, the impact of traffic coming from the south to loop around at Frontage Rd is likely to create a nightmare bottleneck at Exit 18. So, the question is, will the Mass DOT take steps in anticipation of that extra volume or just simply let it all pile up?
And for traffic coming in from the north, which does most definitely rely on the Callahan Tunnel as it's direct route to the airport, getting off at Route 16 and sitting on Route 1 is going to be no picnic. Commuters in Revere should expect that portion of Route 1 towards the airport to become a parking lot at many hours of the day.
Commuters from the tony W towns and other points west will see no change. The Ted Williams tunnel will be a bit more crowded but really it won't be much different for them during this project. And thus the reality will be that if you can get to the airport via the Mass Pike, and many do, that this will remain a good bet with only city traffic at rush hour being your issue. However remember that the Mass Turnpike has no eastbound entrance between the Allston/Cambridge tolls and the expressway. And that means that the entire Back Bay, Copley and Fenway areas really have no particularly good way to get to the TW tunnel.