Two commuter trains collided in Boston’s Back Bay region today, sending at least six to the hospital and 20 others are being medically evaluated at the scene. An MBTA spokesman said one trolley “bumped into another” shortly before noon, but that the cars remained on the track and showed no visible damage. None of the injuries were deemed life threatening, officials said, adding that they are investigating a possible cause for the collision. In 2009, an MBTA conductor was text-messaging when he rear-ended another trolley. Let’s hope this crash had nothing to do with reckless behavior behind the wheel.