Followers of this blog will recall that nearly a year ago I started doing simulations for various MBTA commuter rail lines under plausible operating schedules for TransitMatters’ Regional Rail proposal. Since I live in Framingham, I concentrated mainly on the Framingham/Worcester Line, which is one of the easiest to schedule: there are only two intercity trains per day, and the entire line is double-tracked the full distance from Worcester to Boston. (Substantial parts of it used to be triple-tracked, and there’s a study in the works to determine whether the third track should be restored to simplify scheduling express service.)

The Providence Line is significantly more complicated. Not only are there three MBTA branch lines that feed into it — the short Stoughton Line, the much longer and heavily used Franklin Line, and the Needham Line — but there are also a dozen Amtrak trips a day which get priority access to the tracks. The Needham and Franklin Lines are somewhat easier to deal with: as I’ve written before, the Needham Line should be turned into an extension of the Orange Line, and in the mean time even Rail Vision is assuming it can be short-turned at Forest Hills peak hours; the Franklin Line was historically interlined with the Fairmount Line through Dorchester and could easily be operated that way again. (In fact, a number of Franklin Line trips each day already operate this way; all that is needed is better platforms at Readville to allow transfers between the Fairmount/Franklin and Providence Lines.) The Stoughton Line and the Amtrak trains, however, have to be integrated with the Providence Line schedule, and that creates complications for implementing Regional Rail on what pretty much everyone agrees is the line that should be done first. I’ve created a “string diagram” that shows Amtrak and Stoughton Line service during the morning commuting hours:

Stringline showing northbound Amtrak and Stoughton trains

Note that the scheduled performance of Northeast Regional train 66, the only Amtrak train that operates along the line during morning rush, is pretty dismal compared even to the other northbound Regional, train 190. This will be an issue when we start trying to schedule fast EMUs around the lumbering locomotive-hauled Regional. The Providence Line, although it is built on a mainly three-track right-of-way, is presently limited to only two through tracks between Pawtucket and Readville, and even after substantial investment has geographic bottlenecks (around Route 128 in Westwood and through Mansfield) that make a dedicated express track uneconomical.

The next challenge is the southbound (return) track capacity. I did not model this in as much detail, but it presents more of a problem because the basic tenet of Regional Rail is that you don’t keep peak-service trains close to the city, you send them back to their out-of-town terminal immediately, in revenue service — and during peak hours there are substantially more southbound Amtrak trips that have to be worked around. The following diagram shows those trains:

Stringline showing AM southbound Amtrak and Stoughton trains

The final challenge is seating capacity. I used the same simulator as I previously implemented for the Worcester Line, and the 2018 CTPS passenger counts, to estimate the 90th percentile passenger loads on various service schedules that seemed to be practical with only minor shifts in existing Stoughton Line operations. I am assuming for the purposes of this simulation that the Stoughton Line continues to operate as a diesel service with the current (2019) schedules, because actually building electrification and new stations on the Stoughton Line will be expensive and time-consuming, and might well be deferred until South Coast Rail phase 2 advances. I used the trip-time modeling provided by Alon Levy, as with the Worcester Line simulations. Alon’s trip-time model assumes that service within Rhode Island is de-linked from the MBTA service; the 49-minute trip time from Providence to South Station (making all local stops!) is close to ideal, with an 11-minute turnaround time at both terminals allowing for a single consist to complete a full round trip in exactly two hours. I assume the proposed new Pawtucket station will get built, and I also assume a new infill station at Cummins Highway in Roslindale. After doing all that, I simulated a basic all-local service with 15-minute headways, and got … a service that is either extremely crowded or physically impossible.

The problem that I ran into is that not only is the Providence Line heavily used during peak periods, but that crowding is concentrated into a small time window, and it happens mostly at the southern end of the route — rush-hour trains 806 and 808 each leave Sharon with more than 1,100 passengers, and Attleboro train 842 leaves Sharon with nearly 800 on board. The sort of single-level articulated EMUs that I favor for Regional Rail have a seating capacity of 250 to 280 seats — the Finnish class Sm5 that I simulated for Worcester is at the low end, but a train that’s 5 meters longer (267 instead of 249 feet) would hold about 280 seated and, at crush loads, about another 250 standees. The MBTA does not currently have a comfort standard for commuter rail, but in my simulations I’ve decided that the 90th percentile passenger load should always get seated (and the more emphatically so the longer riders would be required to stand if seats are all taken). The MBTA’s platforms are 800 feet long, so if you have an 80-meter articulated EMU, you can platform a train of three of them, with a total of 840 seats — we really don’t want to have a situation where we’re 20 minutes away from South Station and there are already a hundred standees on the train.

I tossed a few ideas back and forth, but they tended to run into problems when faced with the physical realities on the line. Running more frequent service — ten-minute headways or better — is a nice idea in theory, but my simulator was still coming up with numbers that don’t work. At higher headways, the coordination problem with Amtrak and Stoughton Line trains is much worse, especially with the slow Stoughton diesels, and you also run into serious capacity problems at South Station. (My 8 trains per hour Worcester service only requires two platforms, but for Providence, Stoughton, and Amtrak together you need at least five. Of course, North-South Rail Link will eventually fix this, if we can just manage to build it before the MBTA studies it to death.) So I started to experiment with different service variations that would take some running time off the route — but not too much running time, because you don’t want to catch up to the previous departure when there’s no possibility of passing. Such a variation would also need to pick up enough of the passenger load to knock down the peaks that the regular local service experiences, but not too much.

I eventually hit on the idea of a limited-stop service that picks up passengers at three of the busiest stations along the line — Providence, Mansfield, and Sharon — but leaves the other stops to be serviced by a local train. This variant takes 38 minutes to run, saving 11 minutes over the regular service making all stops. That works out nicely, because it means that a limited-stop train can leave 13 minutes after a local train and still arrive at South Station two minutes later, so it fits nicely between locals running on 15-minute headways, and at the midpoint of the run, in Mansfield and Sharon, the limited is evenly spaced between the two surrounding locals. The limited would also stop at Route 128 and Ruggles stations. This service pattern gives a string diagram that looks like the following:

The diagram shows four local trains per hour, four peak-period limited trains per hour, plus existing Stoughton Line and Amtrak trains as currently timetabled.

In the simulation, the heaviest load is on the 7:39 limited (arriving 8:17 at South Station), shown as V497L in my timetable, with 774 passengers — still well below seated capacity, so there’s plenty of room for growth. The preceding two trains get about 670 each, and the next train is under 500, leaving plenty of options for riders who miss their regular train. Amtrak’s Northeast Regional train 66 remains a problem; the clockface schedule would demand a train V465, arriving at 7:45, but this conflicts with Amtrak. I’ve dropped that run, leaving two consecutive limited trains on either side of the Amtrak (assuming it’s even on time), and as you can see from the diagram, the second of those still conflicts with Amtrak. I’m going to assume that this can be managed by getting Amtrak onto the third track north of Readville, and perhaps some minor schedule adjustments. There are a few other minor conflicts with Stoughton Line trains that can be managed by timed meets at Canton Jct. and some minor schedule adjustments.

One question that arises is what to do about the 14 EMUs on the “limited” pattern once they arrive at South Station. Obviously it is necessary to get them out of the terminal as soon as possible (that will still take about ten minutes due to mandatory safety checks and the time it takes for the operator to switch ends), but there isn’t the southbound demand for eight trains per hour. The fastest reasonable cycle time, with the southbound return trip running non-revenue, would not get the first northbound “limited” consist back to Providence in time to make another trip. Probably what makes the most sense in this case is for these trains to provide additional urban service to Readville and then go out of service until needed for the evening peak. As I’ve built this schedule, frequency drops at midday to only two trains per hour, but it wouldn’t hurt to maintain four trains per hour all day; this would provide better equipment utilization and reduce the need for midday storage space in Rhode Island. The total car requirement is 30 EMUs to operate this service; at $8 million each, that’s $240 million in rolling stock, and would free up a substantial number of old diesel locomotives and coaches to improve comfort and reliability on the yet-to-be-electrified lines. (Additional EMUs would be required to operate the intra-Rhode Island shuttle service, but the cycle time is 90 minutes, which would require just three EMUs.)

The full details are available in the providence branch of my GitHub repo. If you’re not super into methodology, you can just skip to the summary spreadsheet, which gives trip times, schedules, passenger loading, equipment requirements, and the CTPS 2018 passenger boarding statistics. (Unlike with the Worcester Line, I did not complete a full equipment plan; with a two-hour cycle time it was easy enough to just count the turns and figure the maximum loading on each consist.)