The Silver Line
Boston is a city but not just any city. The Silver Line is a bus but not just any bus. It's a tunnel seeking, satellite driven, traffic light changing, kiosk talking, two section 60 foot long vehicles powered by natural gas, electricity, and a diesel generator. When the Silver Line's $1,500,000,000 of construction is complete, it will travel most of its route between Roxbury and Logan Airport underground.
Kibitzing with four satellites in outer space, the Silver Line vehicles change traffic lights to green, in their favor, at the major intersections along Washington Street and explain arrival times to anxious passengers at kiosks along their trip to Chinatown. The buses pass over the Massachusetts Turnpike and disappear under Tremont Street as they dive below one of America's first subway tunnels opened on October 1, 1897 and abandoned on April 6, 1962.
The new Silver Line tunnel, mined under the old one, connects to Boston Common and the Green Line at Boylston Street. Passing beneath the Green Line, the subterranean buses turn right and head for South Station. En route, the Silver Line vehicles pass below the Washington Street Orange Line tunnel built in 1908. Continuing under Boylston/Essex Street the vehicles dive under the six-lane, Dewey Square highway tunnel, now I-93, built in 1959.
Leaving South Station, the buses move under Atlantic Avenue but just barely above the Red Line subway tunnel built in 1916. At Congress Street they veer for South Boston and pass through the historic foundations of Russia Wharf. The Silver Line then uses three prefabricated tunnel sections, called immersed tube tunnels (ITT's), to progress under the Fort Point Channel in Boston Harbor. Each ITT section is 233 feet long and weighs 6160 tons.
After stopping at the Moakley Courthouse, the Silver Line system makes an underground connection to the World Trade Center. Here, the transit drivers turn a key to activate on board diesel generator-engines and power down their electrical units before driving out of the tunnel. Once above ground, some of the rapid buses seek out and drive into the Ted Williams Tunnel, opened in 1995, cutting in front of all the other tunnel traffic by using a special ramp. Heading to Logan Airport a mile and a half away, the Silver Line vehicles pass beneath Boston Harbor. At the airport, they make stops at each of Logan's newly built terminals. In the Seaport District, other Silver Line vehicles pop out of the same World Trade Tunnel but drive to the new convention center or towards Dry Dock Avenue.