MBTA to install $80M underground cable network to prevent train collisions

May 24, 2023

The MBTA will spend roughly $80 million to install an underground fiber cable network, which will aim to improve safety across the commuter rail system and reduce service disruptions.

The new infrastructure will gradually replace the aerial fiber network that the T implemented in 2020 to support the federally-mandated positive train control system.

All commuter and freight railroads are required to operate PTC, which monitors train movements to prevent collisions and derailments.

"We’re going to transition the communications portion of that system from the aerial network to the new buried network," said Project Manager Jaime Garmendia. "This helps protect the communications of the system.

"Buried fiber is a lot more resistant to extreme weather and the impact of third-party activities, whether that's construction, accidents (or) treefall."

Garmendia said the existing aerial network has experienced fiber breaks at a higher rate than expected over the past couple of years.

A "fair amount" of spare fiber was built into the system in anticipation of about five breaks per year, but more than triple that number, or 16, occurred last year, he said.

Each time a break occurs, and a new splice is introduced into the system by joining two fiber optic cables together to repair the damage, the quality of the communications infrastructure degrades and its reliability decreases, Garmendia said.

And as the network's built-in spare fiber dwindles, he said, more commuter rail service disruptions are needed to complete those kinds of repairs.

"So, the intent of this project," Garmendia said, "is to bury a new fiber optic cable network in the right of way itself to improve the system resiliency and allow for that 100% uptime."

The underground cable installation will start on the Fitchburg and Lowell lines, where the most fiber breaks have occurred, and continue on future rail lines as more funding becomes available, Garmendia said.

The project will also connect the new commuter rail dispatch center at Iron Horse Park in North Billerica, part of the Lowell Line, to the existing wayside signal system, he said.

The work will be carried out by Boston-based McCourt Construction Co., as part of a $78.81 million contract approved Thursday by the MBTA Board of Directors.

The contract also includes two options, totaling $12.96 million, for the installation of additional fiber optic cable infrastructure in the same conduits on the Fitchburg and Lowell lines, Garmendia said.

"We’ve had buried fiber for over 20 years on the Old Colony Lines," Garmendia said, referencing the branches that connect the South Shore to downtown Boston. "And it's been very easy to maintain compared to the aerial network we’ve had for only a few years."

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