The Massachusetts Bay Transportation Authority (MBTA) has announced that it has identified the causes behind recent incidents of dead trolleys on the Green Line Extension and older tracks near Copley and on Beacon Street. The agency is taking measures to prevent similar issues from occurring in the future.

The first disruption took place on October 20th between Science Park and Lechmere, where passengers were left stranded inside a trolley for a prolonged period of 90 minutes. After conducting an investigation, the MBTA discovered a broken overhead catenary system (OCS) cutout in the area. The Green Line Extension, being a new "constant tension" system, relies on cables, pulleys, and weights to maintain the appropriate tension on the OCS power lines. The MBTA believes that this specific cutout failed prematurely and is an isolated case.

In the other three incidents near Copley and on Beacon Street in Audubon Circle, the issues were identified as a result of using older parts in the MBTA's legacy system. This system, known as a "static tension" system, lacks the ability to self-adjust and tighten wires. The recent severe temperature swings that have taken place are suspected to have caused the wire system to sag, wear, and eventually break.

To prevent future power issues within the legacy system, the MBTA is exploring the possibility of upgrading its inspection technology. The introduction of new cameras and sensors would enhance the detection of defects and weaknesses in the wire system. As an immediate measure, the MBTA's Power Department is intensifying inspections on the most sensitive sections of the Green Line and has already replaced approximately 200 feet of OCS wire.

These initiatives aim to ensure the smooth and reliable operation of the MBTA's rail network. By addressing the specific issues on the Green Line Extension and improving inspection methods for the legacy system, the MBTA is working towards minimizing service disruptions and providing a better experience for passengers.

As the MBTA continues its efforts to resolve these power-line challenges, commuters are advised to stay updated on any potential service changes or delays. By leveraging modern technology and proactive maintenance, the MBTA aims to enhance the overall efficiency and dependability of the Green Line and the entire subway system.