People I respect are asking me about alternative routes for intercity trains into Boston. So let me explain why everything going into the city from points south should run to South Station via Providence and not via alternative inland routes such as Worcester or a new carved-up route via Woonsocket.
As an explanation, here is a map of the region’s commuter rail network; additional stations we’re proposing for regional rail are in turquoise, and new line segments are dashed.
Observe that the Providence Line, the route currently used by all intercity trains except the daily Lake Shore Limited, is pretty straight – most of it is good for 300+ km/h as far as track geometry goes. The Canton Viaduct near that Canton Junction station is a 1,746 meter radius curve, good for 237 km/h with active suspension or 216 km/h with the best non-tilting European practice. This straightness continues into Rhode Island, separated by a handful of curves that are to some extent fixable through Pawtucket. The fastest segment of the Acela train today is there, in Massachusetts and Rhode Island.
The Worcester Line is visibly a lot curvier. Only two segments allow 160 km/h running in our regional rail schedules, around Westborough and immediately west of Grafton. This is why, ignoring intercity rail, our timetables have Boston-Providence trains taking 47 minutes where Boston-Worcester express trains take 45 minutes with 4 fewer stops or 57 minutes with 5 more, over the same route length. And the higher the necessary top speed, the larger the trip time mismatch is due to curves.
Going around the curves of the Worcester Line is possible, if high-speed rail gets a bypass next to I-90. However, this introduces three problems:
- More construction is needed, on the order of 210 km between Auburndale and New Haven compared with only 120 between Kingston and New Haven.
- Bypass tracks can’t serve the built-up area of Worcester, since I-90 passes well to its south. A peripheral station is possible but requires an extension of the commuter rail network to work well. Springfield and Hartford are both easy to serve at city center, but if only those two centers are servable, this throws away the advantage of the inland route over Providence in connecting to more medium-size intermediate cities.
- The two-track section through Newton remains the stuff of nightmares. There is no room to widen the right-of-way, and yet it is a buys section of the line, where it is barely possible to fit express regional rail alongside local trains, let alone intercity trains. Fast intercity trains would require a long tunnel, or demolition of two freeway lanes.
There’s the occasional plan to run intercity rail via the Worcester Line anyway. This is usually justified on grounds of resiliency (i.e. building too much infrastructure and running it unreliably), or price discrimination (charging less for lower-speed, higher-cost trains), or sheer crayoning (a stop in Springfield, without any integration with the rest of the system). All of these justifications are excuses; regional trains connecting Boston with Springfield and Springfield with New Haven are great, but the intercity corridor should, at all levels of investment, remain the Northeast Corridor, via Providence.
The issue is that, even without high-speed rail, the capacity and high track quality are on Providence. Then, as investment levels increase, it’s always easier to upgrade that route. The 120 km of high-speed bypass between New Haven and Kingston cost around $3-3.5 billion at latter-day European costs, save around 25 minutes relative to best practice, and open the door to more frequent regional service between New Haven and Kingston on the legacy Shore Line alongside high-speed intercity rail on the bypass. This is organizationally easy spending – not much coordination is required with other railroads, unlike the situation between New Haven and Wilmington with continuous track sharing with commuter lines.
If more capacity is required, adding strategic bypasses to the Providence Line is organizationally on the easy side for intercity-commuter rail track sharing (the Boston network is a simple diagram without too much weird branching). There’s a bypass at Attleboro today; without further bypasses, intercity trains can do Boston-Attleboro in 11 fewer minutes than regional trains if both classes run every 15 minutes, which work out to 25 minutes per our schedule and around 32 between Boston and Providence. To run intercity trains faster, in around 22 minutes, a second bypass is needed, in the Route 128-Readville area, but that is constructible at limited cost. If trains are desired more than very 15 minutes, then a) further four-tracking is feasible, and b) an intercity railroad that fills a full-length train every 15 minutes prints money and can afford to invest more.
This system of investment doesn’t work via the inland route. It’s too curvy, and the bypasses required to make it work are longer and more complex to build due to the hilly terrain. Then there’s the world-of-pain segment through Newton; in contrast, the New Haven-Kingston bypass can be built zero-tunnel. But that’s fine! The Northeast Corridor’s plenty upgradable, the inland route is bad for long-distance traffic (again, regional traffic is fine) but thankfully unnecessary.