Red Line Extension to Mattapan

A comprehensive look at replacing the old PCC trolleys

Sky Rose
14 min readJan 2, 2018


The Mattapan High Speed Line is old and difficult to maintain. MBTA is currently looking at future options on how to maintain transit service along that corridor. As far as I know, there are 4 options:

  • Do nothing, and continue to maintain the PCCs.
  • Replace with a modern light rail vehicle.
  • Replace with bus service.
  • Extend the Red Line

I haven’t seen much discussion on that last option, so this post aims to be a comprehensive view on what it would look like. It’s a mix of collecting others’ discussions and some original ideas.

I think it’s a good idea, so I talk pretty glowingly about it, but this is meant to inspire conversation rather than convince you that it’s the best plan.

The conclusion is that extending the Red Line to Mattapan is way more realistic than it first seems, and while it’s not a clear winner, it certainly deserves a closer look.

Some disclaimers: First, I’m not an engineer, and I tried but failed to find useful budget numbers / cost estimates. If you can provide expert opinions or data on either of those topics, I’d love to hear from you and will update this analysis accordingly.

Second, I work for the MBTA, but in an unrelated area. This is a personal project done in my free time and doesn’t represent the MBTA.

Quick Outline

The Red Line would get two new stops: Milton and Mattapan. This would serve 92% of current boardings and alightings (including Central Ave, since it is so close to Milton), while the recent Neponset Trail and new pedestrian connections would provide easy access from the closed stops.

Vastly improved capacity and service would mean greatly increased ridership and mobility to the area. Travelling from Mattapan northward to the Red Line would get an average of 8 minutes faster, but equally importantly, would become less variable as well.

I don’t have the numbers or skills to do a real cost estimate, but my back of the envelope amateur calculations are that the conversion could be done for about $300 million in capital expenses, and it would reduce operating/maintenance expenses. A pretty good deal for such a huge increase in service, where something needs to be done anyway.


Current Ridership

The most recent ridership data I could find was in the 2014 Blue Book, from a 2010 ridership survey. It’s old, but I think the patterns hold up.

Screenshot from the Blue Book and a few other ways of looking at that data.

The key takeaways here are:

  • Most people ride end-to-end. Mattapan and Ashmont account for 76% of boardings and alightings.
  • Central Ave and Milton, which have bus connections and are in a denser area, are most of the rest.

Closing the four smallest stations (Capen St, Valley Rd, Butler, Cedar Grove) will reduce service to the 8% of boardings and alightings (probably around 15% of trips) that use those stations, while vastly improving service to the 85% of trips that start and end at the hubs (Mattapan, Central/Milton, Ashmont).

Service Improvements

For a person going from Mattapan to Ashmont to connect to the Red Line, they currently spend, on average,

  • 2.5 minutes waiting for a Mattapan Trolley (5 minute headways).
  • 8.5 minutes to travel end to end.
  • 3 minutes transfering through Ashmont Station.
  • 3 minutes waiting for a Red Line Train (The T aims for 6 minute headways on the Ashmont branch with the new cars.).
  • 17 minutes total.

Those times would not change significantly if the line was replaced by buses or modern light rail vehicles.

With the Red Line extension, they would spend,

  • 3 minutes waiting for a Red Line Train.
  • 6 minutes travelling to Ashmont Station.
  • 9 minutes total.

An 8 minute improvement, plus a one seat ride, plus reduced variability due to fewer transfers, would be pretty great. The difference becomes even bigger on the weekends, when trolley frequency drops to up to 26 minutes, while Red Line frequency stays at 15 minutes.

There are also the benefits from having a simpler system. It’s easier to understand and learn, and will more tightly tie the area into the rest of the city.

Combine the speed and understandability with the increased capacity and reliability of Red Line trains over trolleys, and there’s a potential to get a lot more people riding the T.

Note that although the Braintree branch is over capcity, the Ashmont branch is not, especially considering upcoming Red Line capacity improvements. The system will be able to handle the increased load.

Maintaining access to the closed stops.

Although the number of people using the closed stops (Capen St, Valley Road, Butler, and Cedar Grove) is small, people do still use those stops. Making sure that those people have access to the new Red Line stops is important both to those people and to the feasibility of this project.

One way to look at station accessibility is with walksheds. A walkshed is the area around a station where people are willing to walk there. A good primer on this topic is on my favorite transit blog ever, Human Transit, although they don’t use the term “walkshed” in that article. The MBTA Back on Track blog also has a post about walksheds

Crucially, people are willing to walk further to get to better transit service. For the Mattapan trolley, I’d put the walk radius at around 400 meters. For heavy rail like the Red Line, people will walk around 800 meters. Note that these distances are pretty fuzzy. They’re based on what’s typical for those kinds of transit, rather than being tuned for this specific case, and there’s obviously a lot of person-to-person variation in how far people are willing to walk. But since it’s a little easier to do analyses if we choose a hard number, we’ll use 400m and 800m.

Here’s a map of the area, showing the 400m walksheds to the trolley stops compared to the 800m walksheds to the Red Line. Pay attention not just to the area covered, but also to the density of housing and businesses in that area.

Some things to learn from this map:

  • Not very much area becomes so far from a station that it would be no longer worth it to take the T. Valley Road is the biggest chunk of that area, but it also sees very little ridership.
  • Most areas around closed stops would find it worthwhile to walk to the next station.
  • A lot of people in dense areas north and west of Mattapan and some people north of Milton, who currently do not walk to their trolley stops, would find it worth it to walk to Red Line stations.

Having good walking connections is very important to giving the most people access to a transit stop. People who live on Capen Street are currently cut off from walking to Mattapan (it’s a mile to go around to Blue Hill Ave), and depend on the trolley to get there. With a pedestrian path along the tracks over the Neponset River, those residents will have easy access to Mattapan.

Some will prefer being able to walk to a larger station (for example, those on Capen St might like being able to get to Mattapan buses without transfering), while some will miss their stop next door even though it means a transfer. But it’s important to weight those situations by the number of people in them, and also to compare them against the number of people (thousands?) who do not find walking to the trolley worthwhile before but would walk to the Red Line.

In summary, a Red Line extension would increase walking distance for a few riders, but significantly improve service for many more others.

Design and Construction

Here’s the list of what would need to be built:

  • Build two new Red Line stations, Milton and Mattapan.
  • Build two new overpasses to replace grade crossings at Central Ave and Capen St.
  • Replace all track to handle heavy rail and add the third rail.
  • Upgrade the Ashmont branch power feed.
  • Rearrange tracks near Codman Yard and add tracks going south out of the yard.
  • Add security fencing around the ROW.
  • Demolish the Ashmont trolley loop.
  • Rebuild one bridge across the Neponset River.
  • Buy two new train sets.

Milton Station

For good stop spacing and because of ridership patterns, there needs to be one new station between Ashmont and Mattapan. Milton is a slightly better location than Central Ave for that station for several reasons:

  • More equal stop spacing. Milton is exactly in the middle, while Central Ave would give 1 mile / 1.5 mile spacings.
  • Better walking from closed trolley stops. Butler (next to Milton) has 3 times the ridership of Valley Road (next to Central Ave)
  • Central Ave requires a new grade separation, and fitting a station around that would be difficult.
  • A station at Milton can take advantage of the existing Adams overpass for shelter, reducing the amount of structure that needs to be built.
  • Serves a denser area that’s more of a commercial center.

Although Central Ave has higher ridership than Milton, much of that is because buses on that side have higher ridership. The buses that serve Central Ave also come within a block of Milton, and could even be straightened to go down Randolph/Adams.

It’s a tight squeeze to fit a full Red Line station at Milton, though, so I’ve laid out a plan to show it’s possible

The new Red Line side platforms can sit partially under the Adams St overpass. This requires the ROW width that currently goes to the Neponset Trail, so the trail would have to be ramped up to a grade crossing at Adams St.

This may be a good thing for the trail, though, as currently the only access to the trail from Adams St is through a parking lot or down a staircase and across the tracks. The ramps would provide easier, accessible trail access. There is plenty of space on the overpass for the trail crossing. Parking would have to be moved, but not eliminated.

The outbound (northern) platform would join the Neponset trail on both ends. The eastern end of that platform would also get a new staircase and elevator down from Adams St.

On the inbound (southern) platform, there are two adjacent existing staircases: The one that leads to the current trolley stop, and a service staircase for the building next door that leads to an alley. One of those (probably the service staircase) would be replaced by an elevator.

The western end of the inbound platform has just enough space for a staircase up to Elliot st, which significantly shortens walking distances for people coming from the west.

The inbound platform will not have access to the Neponset Trail, except by going up and over the tracks on Adams St.

On both platforms, a second elevator for redundancy is not needed because if the elevators go out of service, the longer step free detours through the parking lots or down the trail ramp still exist. This helps cut costs. That detour is pretty inconvenient, though (150–200 meters of extra distance) so one elevator per platform is still important.

Fare gates are on both ends of both platforms.

By taking advantage of the existing overpass and leaving the western half of each platform exposed, there’s very little new structure that needs to be built, and construction costs could be kept very small. My estimate is that it could be done for $40M.

Mattapan Station

There is plenty of space at Mattapan. There’s the old trolley yard and maintenance shed that would not be needed, room to rearrange the busway, undeveloped forest space, and a parking lot next door. Since the feasibility of building a station there is not an issue, and because building terminals is more complicated and I’m not an engineer, I haven’t attempted to make a layout of the station.

The Ashmont branch only sees half the frequency of the Red Line trunk, so this station only needs to handle half the traffic of Alewife. It’s lower stakes, and if there’s not room to do the perfect setup with trailing tracks and a yard like Ashmont is right now, that’s okay.

Terminal stations are more expensive than intermediate stations, and it’d be difficult to take advantage of previous structures like Milton can, so my cost estimate for this station is $100M.


There are a few bridges along this section.

  • One over Gallivan Boulevard, which already carries Red Line trains to Codman Yard.
  • One over the Neponset Trail, just east of Butler.
  • One over the Neponset River, between Milton and Butler.
  • One over the Neponset River, between Mattapan and Capen Street.

Of these, I’ve heard (but not confirmed) that the last one is the only one that is weight restricted and would need to be replaced. It’s a very short span (60 ft) and rebuilding it would make it easy to add enough width for a path along the tracks.

The cost would be small, and it might be due to be replaced anyway as part of the state of good repair upgrades. Either way, the costs here will not affect whether the Red Line extension is feasible.

Grade Separations

There are only two grade crossings that would need to be eliminated. Both would get an overpass for the trains to go over the roads, since the ramps for a road overpass would disrupt access to houses and businesses. Red Line cars can handle pretty steep slopes (for example, Park St to Charles), allowing the overpasses to be short and cheap.

Capen Street north of the crossing serves only two dozen homes, so this overpass could be built undersized. One lane, and maybe a little lower than usual. The road may need to be adjusted to cross the ROW perpendicularly.

The second crossing at Central Ave is across a busy two lane road, and would be a more standard sized overpass. The ramp up to this overpass limits how far west the Milton platforms can go.

Codman Yard Access / Gallivan Boulevard Overpass

The bridge over Gallivan Boulevard has two halves and carries Red Line cars to Codman Yard and Mattapan trolleys to Ashmont on different tracks. There would need to be some track work so that Red Line cars can get from the western half of that bridge on to the MHSL right of way.

That switchover should happen south of the overpass so that the eastern half of the bridge, which currently holds trolley tracks, could be reused as a pedestrian trail from Cedar Grove to Ashmont.

Worries about losing transit access by consolidating the MHSL’s short stop spacing is one of the biggest barriers to this project, so it’s important that the people currently served by Cedar Grove get good access to Ashmont. Running a pedestrian path along the Red Line tracks from Cedar Grove makes the walk about 100 meters shorter compared to winding through neighborhood streets, and means people don’t need to cross Gallivan Boulevard, which is 4 lanes without a crosswalk within 200 meters in either direction. Like at Capen St, some people may even prefer being able to walk to the buses and Red Line at Ashmont instead of requiring a transfer.

Since the new terminal will be at Mattapan, Codman Yard will need new tracks to go south out of the yard, but there is plenty of room for those tracks. Some trains will start their day at Mattapan, but some will need to deadhead down from Codman in the morning. Since the branch runs at half the frequency of the trunk, there is capacity to fit them in. This is similar to the way Oak Grove is supplied by Wellington.

Red Line Cars

In order to maintain MBTA’s goal of 6 minute headways (3 minutes downtown) on a route that’s extended by 6 minutes, MBTA would need two, maybe three, new Red Line train sets. The most recent contract was $277M for 134 cars. At that rate, 12 new cars would cost $25M.

Construction Cost

These values are very rough, partially because the project is so hypothetical but mostly because I don’t have experience pricing projects. They’re based on others’ estimates and comparisons to similar projects. They also assume that the project is managed effectively and resists scope creep. The goal of this estimate is just to decide if the project is worth further investigation, so that level of roughness should be fine.

The bridge, fencing and trail upgrades are tiny compared to my error bars so I’m ignoring them here.

  • Red Line cars: $25M
  • Milton Station: $40M
  • Mattapan Station: $100M
  • Track upgrades: $30M
  • Overpasses: $40M
  • Codman Yard tracks: $15M
  • Power upgrades: $???
  • Total: ~$300M

So this will not be a billion dollar project, and it won’t be another Green Line Extension. It is possible to do heavy rail extensions at a reasonable price.

Maintenance and Operations Costs

MBTA spends $1.7 Million on maintenance for the trolleys (source), and I don’t think that includes track work or special equipment like Snowzilla. There’s a lot of costs associated with keeping a line open, no matter how small.

The Red Line, on other hand, is running anyway, and two more stops won’t change much about it. There won’t need to be any maintenance shops dedicated for this section of track, or special training procedures, or rare parts kept in stock.

Simpler services are much cheaper to maintain. This is the same reason for standardizing fleets. Maintaining two different kinds of cars is more expensive for the same amount of service than having a single type, and maintaining two different lines is more expensive than one. Operating and maintaining heavy rail is expensive, but a lot of that is fixed costs, and only the marginal costs are relevant.

Unfortunately, I couldn’t find Red Line budget information that was broken up in a useful way for comparing costs to the MHSL, so I can’t make a good quantitative cost estimate, but I’m confident that having a simpler system would reduce costs significantly.

Other Concerns

Cedar Grove Cemetery

The Mattapan Line is the only train line in the United States that runs through a cemetery. The trolleys are not very distruptive, but running louder heavy rail through the cemetery would be. There is some precedent though.

  • Green Line trains run very close to two cemeteries downtown.
  • WMATA’s Blue Line (which is heavy rail like MBTA’s Red Line) runs adjacent to Arlington Cemetery. (Highways run even closer.)
  • Fawkner, Victoria, Australia (a suburb of Melbourne) has a commuter rail station with 20 minute frequency in the middle of a cemetery.
  • The Garden State Parkway runs through the middle of Holy Sepulchre Cemetery in Newark, NJ.

This is definitely something to keep in mind and handle respectfully, but it’s not a deal breaker.


Because the trolleys are so cute and have so much history, there’s a lot of opposition to replacing them with something else. There’s certainly value in having old curiosities around (we spend a lot on museums, after all), but that comes at increased maintenance costs and reduced service, and we have to decide if nostalgia is worth that cost.

There’s a much deeper look at this in Commonwealth Magazine’s article Is there room for nostalgia at the T?


The Mattapan Line won’t live forever, and the MBTA will need to find a cost effective way to maintain or improve service there. The Red Line Extension will be more expensive than other options, but it will be feasible. It would provide substantial service improvements for the thousands of people who use the line and the thousands of people who would use it if it were better, and it’s worth a closer look.




Sky Rose

Putting the trans in transit. I write software for MBTA. This is a personal blog and I don't represent MBTA. they/them