Where improvements in New York and other very large cities can easily include multiple new subway lines, the same is not true of Boston. The concrete pouring would be wasted, since Boston’s existing subway lines are not at capacity. The busiest line, the Red Line, has a peak frequency of one train every 4.5 minutes, which could be doubled with appropriate signaling improvements and more rolling stock if necessary. The Green Line has bigger issues coming from branching – its core segment already runs close to 40 trains per hour – but this could be resolved by obtaining fully low-floor vehicles and lengthening trains to allow one or two extra branches.
Another thing that Boston lacks and other US cities do is very busy bus lines to railstitute. Boston’s busiest bus line is the Silver Line to Dudley Square, which used to be the southern part of the Orange Line and should be light rail; unfortunately, the MBTA rejected it as cost-ineffective (see pp. 36-7) by applying a wrong cost-per-rider metric, as I will explain in a later post. But beyond that, the list of bus lines (p. 50 of the Bluebook) doesn’t contain anything nearly as juicy as New York’s bus lines: New York’s 50th busiest bus is roughly even with Boston’s top bus at 15,000 weekday riders, and its top routes have 50,000, making them obvious choices for subway extensions.
Since Boston does not have a capacity problem requiring more concrete pouring on its subway lines, nor high-productivity buses to railstitute, concrete pouring should focus on the other main reason to build rapid transit: to extend service to areas that do not have it. That’s the main reason to build the North-South Rail Link: it’s as much about direct service from suburbs north of Boston to downtown and maybe Back Bay as about rationalizing service and permitting through-running. As in Philadelphia and as should be the case in New York, through-running is primarily not about suburb-to-suburb service, but about access to job centers near the stations of the other half of the commuter network (in New York those would be at Newark, Brooklyn, and Jamaica; in Philadelphia, at Temple and 30th Street Station and in University City).
The list of concrete-pouring, lines-on-a-map extensions of the MBTA in or near Boston should therefore be limited to required Big Dig mitigations, and not much more. This is not just because they are legally mandated. They are also good transit by themselves – the North-South Rail Link for the aforementioned reasons, the Assembly Square stop on the Orange Line because of the TOD potential, the Red-Blue connection because of the East Boston-Cambridge service need, and the Green Line extensions because they provide much-needed transit service in Somerville that would otherwise need to be picked up by commuter rail, at the cost of good intercity service on the Lowell Line. Apart from these, the only major radial extension that should be pursued is the dismembering of the Needham Line outlined in my last post, in which the Orange Line would take over the portion within Boston and the Green Line would take over the portion in Needham.
What should be done instead of more expansive extension plans is very aggressive use of electronics to make regional rail more useful, recalling that its share of the suburbs-to-Boston market is about one third. This necessitates a lot of concrete pouring as well – on high platforms, on track repairs, on double-tracking some single-track segments, and on other things that do not show up easily on maps – but much less than adding tunnels.
The one difficult bit of concrete pouring that has to be done, in conjunction with the North-South Rail Link, is grade-separating the junctions that lead up to North and South Stations. Without the rail link, the South Station throat is such that, run right, it’s operationally at least two stations (one for lines serving Back Bay, one for the rest), and as many as four (Worcester, the lines feeding into Ruggles, Fairmount, and Old Colony and Greenbush); this allows for zero-conflict moves, higher capacity than the MBTA thinks, and a system in which delays on one line do not affect the others. With the rail link, those two to four systems need to feed into one track pair in a way that avoids opposite-direction flat junctions. The need for grade separations right in the station throats would add substantially to the cost of the rail link over a simple two-track tunnel; that’s why I’m not instantly dismissing it as something that at normal-world costs would take a relatively trivial $500 million.
Despite the rail link’s cost, the electronics are themselves substantial. Signaling improvements are also required, to enable tighter overtakes. Moreover, full electrification should be non-negotiable – the MBTA’s stop spacing may not be as close as that of Metra or the LIRR or Metro-North or SEPTA, but it’s short enough that electrification would make a significant difference in performance. It also interacts interestingly with FRA waivers: on the one hand, without electrification, there are no good FRA-compliant trains – the Colorado Railcar DMUs have mediocre performance and are expensive and vendor-locked, and locomotive-hauled trains have terrible performance. With electrification, there exist decent FRA-compliant trains, but there also exist very good noncompliant trains. According to the Fairmount Line DMU document, current trains have a total acceleration-only penalty of 70 seconds to 60 mph, and Colorado Railcars shave that to 41 (see chart on p. 10); judging by timetable differences and dwell times, the best compliant EMUs lose about 20-25, and judging by YouTube videos FLIRTs lose 13.
The timetable examples I’ve put out – for the Providence Line in past posts, and for the Lowell Line in comments – are very ambitious, and require the signaling, electrification, and rolling stock to be perfect. The costs are not very high by US standards, but are nontrivial. Electrification costs a little more than a million dollars per kilometer (or about $2 million per mile), though it’s unclear whether this is based on route-km or track-km, as one citation I have is for a single-track line and another does not make it clear which one is under consideration. The cost is thus either about $750 million or about $1.5 billion, exclusive of rolling stock. But the benefit is commuter trains that can beat the freeways while also providing adequate regional service and connect to urban rail.