MBTA's Max Speed?

I'm curious, what is the max speed of each of the different modes of MBTA rail transportation?

I'm pretty sure the commuter rail maxes out at 79 mph. Why though? Is that just the limit they choose for fuel efficiency purposes? Or is there some other factor? Does maintaining the track to higher standards get exponentially more expensive?

What about each of the four subway lines?

The maximum speed on the Green Line has been about 50 MPH and that is for some spot out in the middle of the Riverside (D) branch on the surface. I think the maximum speed anywhere in the subway is 30 MPH, at some point point between Hynes and Copley.

I think the maximum speed on the Red Line has been about 65 MPH and that is at some point between FK Umass and Braintree.

Today those spots may be in locations with speed restrictions due to need for track repairs.

The commuter rail is under FRA regulations, that set speed according to track class and safety/signal systems. 79mph is the limit for block signaling without cab signals, ATS or ATC, etc.

I remember peering through the window behind the operator on a Red Line train in the 1970s between Harvard and Central and observing that the speedometer got up to 50 mph. But that was a long time ago, and my memory may be faulty.

I also remember the "8 minutes to Park Street" sign on what is now the newsstand building but used to be the entrance to the Harvard Square station before the extension to Alewife was built.

By contrast, the other day I left myself 30 minutes to catch a train out of South Station when boarding at Central, and missed the train by less than a minute.

I'm fairly positive that all MBTA Rapid Transit maxes out at 40 mph, I have never been on a Red Line train and felt like it was going 65 mph, nor have I ever seen one appearing to be going anywhere near that speed, the old aluminum bodies would probably fall right off their bogies if they ever tried running that fast .
As for Commuter Rail, I do remember someone telling me once that sets with HSP46s leading all bilevels are permitted to run 90 mph on the Attleboro Line (NEC), though I am not sure this is true. I do wish Commuter Rail could be sped up to 90 mph on any section where possible, as I am fairly sure that it could physically be done on a good amount of the current trackage system wide, especially on the Providence and Old Colony Lines, where the good spacing between stations and relatively straight tracks would definitely allow for such speeds to become normal.

According to Amtrak's current ETT, MBTA locomotives are limited to a max speed of 100 MPH when running with a train except for:
010/011 - limited to a max speed of 90 MPH with train
904 - limited to a max speed of 60 MPH with train
3248/3249 - limited to a max speed of 70 MPH with train

All MBTA passenger cars (regardless of manufacturer or model) are limited to a max speed of 80 MPH.

Red line max is 50mph, when it first opened to Quincy 70mph was the norm only on that branch. Green line in the past was 50mph on Riverside, but cars are now governed to 40mph.

What about Blue?
I remember those old Hawkers seemed to fly through the harbor tunnel in my early days.

The Hawkers on the Orange and Blue originally ran at 50mph, but were speed governed to 40mph because of braking problems. Don't know how fast the Siemens are allowed to run or the CRRCs.

The Highland Branch was built as a railroad, and was fully grade separated around the turn of the 20th century. So it is overdesigned for a trolley line.

Article from Boston Globe on speed restrictions states 40mph is max on the rapid lines:

https://www.bostonglobe.com/2023/12/29/ ... -repaires/

The Riverside "D" Highland Branch used to have higher than 40mph speed.

All MBTA passenger cars (regardless of manufacturer or model) are limited to a max speed of 80 MPH.

Will this be the case with the new Hyundai Rotems coming in? They look like they could run up to 100 if they wanted to get service going faster.

It's not an issue with how fast the builder designed them to run - it's how fast Amtrak will allow them to run. That's as much political as it is mechanical.

Commuter Rail and "Rapid Transit" have two different sets of rules and speed limits. Commuter Rail should be higher than 40 already. The systems have different federal regulators and different operators - In-house MBTA vs Keolis (or in the future also Amtrak).