The Northeast Corridor Should not Host Diesel Through-Service
The vast majority of traffic on the Northeast Corridor comprises captive trains, only running internally to the corridor. However, a noticeable minority of trains run south of Washington, swapping the electric locomotive for a diesel locomotive. Those trains have a certain logic to them today – through-service is valuable, and north of Washington they more or less substitute for Northeast Regional service. But drawbacks to reliability remain, and if the corridor modernizes its operations, they will need to be removed; several elements of modern operations are not compatible with keeping either the Virginia trains or the long-distance ones on the corridor. Instead, these trains should be cut to Washington, with transfers to much faster, more frequent Northeast Corridor trains. Potentially, some Virginia lines could be electrified and then through-service could be offered, if they can fill the same size of train that future Northeast Corridor service could.
Fortunately, this tradeoff still leaves the South with better service than it gets today. The forced transfer considerably speeds up the trip for New York-bound passengers, by more than the average transfer penalty even for passengers with heavy luggage. Nonetheless, a tradition of direct through-service from New York to diesel territory in the South will need to end.
Future Northeast Corridor service
Upgraded service, for example in our ongoing project at Marron for how to blend intercity and commuter rail on the corridor, should have all of the following features:
- High speed: our current timetables have New York-Washington trains taking 1:53, at a top speed of 320 km/h; a blanket speed restriction to 217 km/h, the upper limit of the catenary today, would only slow down the trains to 2:04, the rest of the difference in speed from current trip times coming from reliability improvements, higher curve speed, higher acceleration, and minor curve fixes.
- All-EMU configuration: nearly the entire world passenger rail market is electric multiple units rather than separated locomotives and coaches, EMUs outperforming locomotive-hauled cars in every aspect, and the exceptions are the less modern intercity and regional lines.
- Single-class service: trains may have first- and second-class seats, but the trains should not be differentiated by speed – Spain has trains of different speeds on its high-speed line and charges more for the faster ones, and the resulting hit to frequency and interchangeability of tickets explains why Europe’s longest high-speed rail network has a fraction of the per capita ridership of France, Germany, or Japan, which (largely) lack this misfeature.
- Affordable fares: the average fare should be in line with French and German norms, around $0.15 per p-km.
A train that does New York-Washington for a bit less than two hours and charges a bit more than $50 one-way on average – the current average is $106 on the Regional and $192 on the Acela – can comfortably expect ridership to quadruple, based on my two usual references on elasticity of high-speed rail ridership with respect to travel time and fares (Börjesson says -1.12 and -0.61 respectively, Cascetta-Coppola say -2 and -0.37 respectively). This forces running more frequency and longer trains. Frequency is a welcome addition provided there is capacity on the tracks for it; fortunately, there is capacity for an intercity train every 10 minutes in a post-Gateway timetable. The trains in question should be as long as possible, with platform lengthening where necessary to support 16-car trains, to maximize capacity.
The incompatibility of diesel trains
Very few diesel trains run on the Northeast Corridor today, and none run by Amtrak. The through-trains to the South run with engine changes: all Amtrak service today is run with locomotives, and at Washington, the trains change between diesel and electric locomotives. Nonetheless, even electric locomotive service as it is conceived today is incompatible with Northeast Corridor modernization, and future changes would still not make it compatible.
First, to the point on capacity: there is no way to run 16-car trains into the South. There isn’t enough demand for such trains. The Silver Star today runs nine coaches and the Silver Meteor runs 10, and on both trains, three coaches don’t sell seats but are used for baggage, lounge, and dining; the Palmetto runs six coaches, the Crescent seven, and the Cardinal five, each including two non-seat selling coaches. Speeding up the Northeast Corridor by an hour and a half can lead to ridership explosion internally to the corridor, but not on trains that take 30 hours today.
And second, there is no reasonable rolling stock for this, even if there were demand for a train with 16 cars or close to it. Locomotive-hauled trains would necessarily run slow, compromising not just top speed but also acceleration and, owing to the current equipment’s problems, reliability. The example train we’re using in our calculations, the Velaro Novo, has a power-to-weight ratio of 20 kW/t and an initial acceleration rate of 0.65 m/s^2. A pair of ACS-64 locomotives dragging 14 Airo coaches gets 14 kW/t but cannot accelerate faster than around 0.25 m/s^2 at any speed. The unpadded trip time for high-speed rail making one stop per state is 1:46; the unpadded trip time with the additional acceleration time of this example train and with a 217 km/h (135 mph) speed restriction is 2:09. If the timetable buffer time is still 7% then the trip time is 2:18, which means the train would be overtaken by about two faster trains, and this in turn would slow the trains further as more schedule contingency would be required for this more complex system. If the ACS-64’s problems or any interface with the freight-run Southern network forces more padding, then make it three overtakes.
The TGV used to couple a diesel locomotive in front of a high-speed trainset to reach Les Sables d’Olonne, before the branch to it was electrified. This option would eliminate the speed difference on the Northeast Corridor, but would also mean that expensive 16-car high-speed trainsets would be spending an entire day going to Florida at low speed and another going back, without being able to make back the cost through intensive operations measured in train-km per day.
Exceptions and the tail wagging the dog
The basic reason for prioritizing the Northeast Corridor’s internal traffic over through-traffic is the large mismatch in travel volumes. In fiscal 2023, the Northeast Corridor got 12,122,466 riders. The Virginia services got 1,300,776, the Carolinian 315,781, and the long-distance trains 1,308,211. A 4:1 ratio should tilt planners toward prioritizing the core over the long-distance trains.
Note that I have not, up until now, talked about Keystone service and trains to Springfield. This is because Keystone trains can run through to the corridor just fine. None of the reasons why the long-distance trains cannot do so applies: the Keystone corridor is electrified all the way to Harrisburg, and New York-Philadelphia is a significant enough portion of it that boosting speeds in the core (and acceleration everywhere) would lead to sufficient ridership increases to justify 16-car trains. Springfield service is currently unelectrified, and Amtrak generally runs shuttles with timed connections because of the mismatch in demand; it should be electrified, and through-service instituted.
On Keystone and the New Haven-Springfield line, the mismatch in capacity actually works in favor of through-service. The New York-Philadelphia section has the most demand, so having one third of the trains branch off to Harrisburg rather than continuing to Washington is a good way of assigning capacity. New Haven is not Philadelphia, but has so much commuter demand to New York that giving New York-New Haven an intercity train every 10 minutes is not so stupid; in contrast, unless a lot more is built, I suspect that 16-car trains running every 10 minutes between New York and Boston would end up emptier than most planners would prefer. Years ago, before I started looking at the track charts and the possible schedules systematically, I even used the greater demand of New York-Philadelphia to argue in favor of diverting some trains not just at New Haven to Springfield, but at Penn Station, to Jamaica and Long Island; as it is, my primary argument against sending intercity trains to the LIRR is timetabling complexity.
With Keystone and Springfield added back in, the traffic on the Northeast Corridor rises from 12,122,466 to 13,680,273. The ridership of the trains to the South that are to be cut from the corridor is 2,924,768, or 21% of the internal ridership; the tail should not wag the dog.
Is this even bad for the trains to be cut?
No. As mentioned above, the trip times would get a lot faster, it’s just that turning a 30-hour trip into a 28-hour one does not lead to a large ridership boom.
The extra transfer is annoying, but should be compared with the time cost of both running a slower train to New York and changing the engine at Washington Union Station. As explained above, the slower train would take a minimum of 2:09 between New York and Washington, stopping once per state. The scheduled time would be at least 2:18, and likely more, maybe 2:28 with 15% buffer time. The engine change takes about 20 minutes judging by southbound schedules on Virginia service trains; the wait time at Union Station is much longer northbound, because the train has to have more schedule contingency on the less reliable freight-owned section to make its slot on the more precisely timetabled Northeast Corridor. The most charitable interpretation, ignoring the extra required schedule padding, is that making passengers change trains in Washington would save them 45 minutes minus the wait time for the next train (at most 15 minutes).
The transfer penalty is extensively studied in the modal choice literature. For example, studying intercity trips in the Netherlands, de Keizer-Kouwenhoven-Hofker find that the penalty is 23 minutes, which already incorporates an imputed additional waiting time of 15 minutes. This penalty rises by seven minutes if the transfer is not cross-platform; a cross-platform transfer at Union Station would require the through-tracks to be upgraded with high platforms, as they are currently low-platform. It rises by a further seven minutes for passengers with heavy luggage. Even with all of those penalties, 23+7+7 = 37 < 45. And 45 is in a way a best-case scenario; there is a lot of padding involved in making a long-distance or even Virginia train make a specific slot on the corridor, as opposed to guaranteeing passengers a seat on the next available train, and this adds on the order of half an hour, counting both Alexandria-Washington and on-corridor buffer times.
The upshot is that while trains cannot run through from Virginia to a modernized Northeast Corridor, little is lost in making passengers transfer at Union Station. The transfer penalty is real but limited, even with luggage, and the speed gain from letting such passengers transfer to a faster train is noticeable, if small compared with the total length of a night train trip. It would break tradition, but offer a modest improvement in the quality of rail service on the long-distance trains using the corridor and the Virginia trains, in conjunction with the much larger improvement in the quality of internal Northeast Corridor service.




