Logan Airport
At rush hour it can take 30 minutes to drive from Logan Airport to downtown Boston. Annual air traffic is expected to increase by 63% by 2030. Together with traffic from the expected Suffolk Downs redevelopment (50,000 trips per day) the tunnels under the harbor will be in complete grid lock.
The TMT#2 would go a long way to relieving some of this congestion.
Once leaving South Station the TMT#2 would head to Seaport Station and then to Logan Airport where there would be a station built underneath the central parking garage so that all terminals could directly access the station.
An additional station could be contemplated at the proposed development at Suffolk Downs (with a tunnel extension).