Last week, the MBTA unveiled a plan for replacing the Mattapan trolleys with Green Line cars. It’s a wonderful proposal that affordably solves the accessibility and reliability problems with the existing trolleys. And it’s a clear win among the trolley and bus plans that they studied.
But there’s one option the T has not considered that might be even better: Extending the Red Line to Mattapan.

In Boston, there’s a cynicism about building rail, a feeling that it’s so expensive that we have to make do with the bare minimum to cut costs. The MBTA has dismissed a Red Line extension out of hand, without studying it, on the assumption that it would be too expensive. It wouldn’t be.
By my rough estimates, it would cost about $275 million total to extend the Red Line to Mattapan Square. The agency’s plan to use Green Line cars would be around $190 million.

That $275 million price tag includes two new stations, at Milton and Mattapan, two new overpasses, replacing the track, bridge work, power infrastructure, and supplying enough new trains to keep them coming every six minutes from Ashmont to Mattapan. All of which saves some money by eliminating the need for a dedicated maintenance facility, which Green Line cars would need.

An $85 million premium over using Green Line cars is still a lot of money, so the public would have to get some substantial service improvements for the money. In this case, by building a Red Line extension instead of using Green Line cars on the existing line, you’d get a six-minutes faster trip from Mattapan and Milton to downtown, and you wouldn’t need to transfer at Ashmont. An improvement like that could draw thousands of new people to the new stations.

A Red Line extension would also be cheaper for the MBTA to run and maintain than using Green Line cars. It wouldn’t need the dedicated staff and maintenance facilities required if the Mattapan Line were to remain in place.

There’s a lot of operational costs in keeping even a small line running, and since the Red Line is running anyway, an extension to Mattapan would avoid those costs.

Whether those benefits are worth the cost is up for debate. The estimates I’ve given are very rough, and I’m not an expert. To have an informed discussion about the costs and benefits, we need the MBTA to do a focused study on this and come up with more precise cost estimates.

Unfortunately, in their recent presentation of the plan for the line where they studied and compared using Green Line cars, buses, or other trolleys, they made no mention of the potential for a Red Line extension.

If they won’t seriously study that possibility, we can’t get good budget estimates, we can’t make a good comparison to their favored plan with the Green Line cars, and we can’t say we know we’re making the best decisions about what to do with the line.

This is a $200 million decision and we should not make it without investigating all possible options.

I call on MBTA leadership in charge of the future of the Mattapan Line to seriously consider extending the Red Line. Study it well enough to get real cost estimates and a prediction on how it would improve service and ridership. The first real decision the board will have is in a few months with the Capital Investment Program, which will deal with funding for Phase 2 of the Mattapan Line Transformation. By then, we need to know enough about a Red Line extension to make an informed decision.

We often think of rail extensions as too expensive to be feasible, but that doesn’t have to be the case. In Mattapan, where we need to do something anyway and where there’s such a seamless continuation into the existing Red Line at Ashmont, there might be an opportunity to extend the Red Line and improve service affordably. We just need the MBTA to give that option the serious consideration it deserves.

Sky Rose works for MBTA, but in an unrelated area. This piece does not in any way speak for the MBTA. Find Sky Rose on Twitter @skyqrose.