I rode this line between Boston and North Adams around 1975 on a fan trip, and I rode MBTA commuter rail to Fitchburg and Gardner a couple of times. I’m not suggesting that I’m well informed about it, just that I have some acquaintance with the area and the line. Here are my thoughts after reading the study.
3+ hrs. is a long commuting time to Boston and Cambridge, where most of the jobs would be, and the study indicates that some people would use the train to commute to work. I think that Boston would be the main destination for people on this line, and frequency would help attract riders, but I think that even with five round trips per day, the trains would be lightly patronized west of Fitchburg. (The proposal says that the major destinations for people on the central part of the route are Fitchburg, Leominster, and Gardner. My guess is that the current pattern of trips being local in the central part of the route may be due to the lack of transportation alternatives. Going to Boston, for example, involves a long drive, and using local transportation is slow. The proposal mentions that it’s possible to go 60+ miles from Charlemont to Wachusett [the western end of the commuter rail line to Boston] by local transit but that it takes 4.5 hrs. one way, and a one-day round trip is not possible.) The proposal with lower investment (alternative 1) predicts 66,000 to 111,000 annual riders. With ten trains per day, 365 days per year, that comes to (correct me if I’m wrong) 15 to 30 passengers per train. The highest projection (alternative 3, electrified service—which sounds extravagant to me for ten trains per day) is projected to yield about 83 passengers per train. In any alternative, the trains might have only a few people on board at North Adams.
The projection “assumes that the overall pattern of existing trips will continue …” It does not estimate changes to travel patterns and markets resulting from “changes to the transportation system, in this case, a Northern Tier passenger rail service.” My understanding of the report is that the rail ridership projections are based on how many people would use the train instead of their current mode of transportation for existing trips. But if I understand figure 3.25 correctly, in Leominster, Gardner, Greenfield, and North Adams, more than one-sixth of households do not have a car. If their current trips depend on local buses, then the rail service would offer trips that are not possible without a car at present. The ridership estimates compare proposed rail trip times to Boston with existing automobile trip times (among other data). Providing an alternative to car travel is one of the goals of the proposed service, as is providing mobility where it is now lacking. Maybe the new rail alternative would generate a good number of trips among those many households without cars, in addition to current drivers who switch to rail.
The northern tier ridership estimates are based partly on Fitchburg commuter rail and Downeaster ridership, both of which have Boston as a primary destination, with the Downeaster anchored by Portland on the north end. If the trips on the central portion of the northern tier continued to begin and end mostly in that area, then travel to Boston would not contribute many riders in the towns west of Fitchburg. However, I think that easier travel to and from Boston would generate some additional trips, though I don't imagine there would be a strong market between Boston and North Adams because of the distance and because North Adams is not very big.
“The West segment has a strong north-south orientation for trips …” according to the proposal. So I would suggest that eastbound and westbound northern tier trains meet the southbound and northbound Vermonter at Greenfield (at 1:36 pm and 4:22 pm), with three trains in the station at once to accommodate transfers in any direction. A morning connection to the southbound Valley Flyer at Greenfield would require a very early departure from North Adams and even earlier from Boston. Connections from northbound Valley Flyers could be made at more easily marketable times. If the northern tier service is inaugurated, maybe a later weekday southbound Valley Flyer could be added to accommodate southbound travelers from both directions on the northern tier. The proposal does say that north-south connections at Greenfield would be a consideration for northern tier schedules.
Making Rensselaer the west end of the route (a possibility mentioned in the proposal) would open up more trip possibilities, but getting there via Schenectady, as proposed, would be circuitous and time consuming. If Open Railway Map is correct, the line between Mechanicville and Rensselaer has a max speed of 25 mph, so with a stop at Troy, a passenger train could probably cover it in less than an hour. Even with fast running between Schenectady and Rensselaer, it would surely take more than an hour to cover the longer distance between Mechanicville and Rensselaer via Schenectady. Also, Rensselaer Polytech in Troy might generate traffic both to Boston and the northern tier of Massachusetts as well as to the New York metro area via connections at Rensselaer.