Did the big dig actually ease traffic in downtown Boston? Maybe not:
Despite being a national embarrassment, advocates say the Big Dig has achieved its goal of alleviating traffic in Boston, and they’re right. In 1994, getting from one end of Boston to the other using the Central Artery took 15 minutes — today it can usually be done in three minutes or less. Back in the day, traffic jams on the the artery could last up to 14 hours a day. Today, the Big Dig tunnels are almost always clog free.
But move out from the center of Boston, and things don’t look quite as rosy. After examining scores of state highways records, the Globe concluded that at points north and south of the city, congestion has gotten worse since the opening of the Big Dig, sometimes quite a bit worse. At one 11 mile strip just north of the city, evening commute time has more than doubled, from 12 minutes to 25. Similar increases can be seen at other points outside Boston on the roads leading into the tunnels.
Why? Because with such a sleek, streamlined new highway in place, more and more suburbanites now choose to commute into Boston by car. That would be ok if the highways leading into the city from the North and South had been expanded in conjunction with Big Dig construction, but they weren’t. Prior to the Big Dig the main road into Boston worked like an hourglass — a wide pathway that narrowed as you approached the city, and then opened up on the other side. But now the shape has changed, with the road underneath Boston wide open, narrowing as you move north or south away from the city.
This is what we call “induced demand,” folks.