The Regional Plan Association has a detailed regional rail proposal out. It’s the same one from the Fourth Plan that I’ve criticized here, on Streetsblog, and on Curbed, but with more explanation for how the service should run, with stopping patterns and frequency.
There are some good aspects there, like a section about the importance of electrification and multiple-units, though it stops short of calling for full electrification and replacement of locomotives with EMUs; the focus on off-peak frequency is also welcome. There are also bad ones, like the claim on p. 32 that it’s difficult to impossible to provide through-running using the existing Penn Station tracks used by New Jersey Transit. Foster Nichols told me that there are some difficulties with grades but they should be doable if NJT commits to an all-EMU fleet, and reminded me that the ARC studies judged through-running using these station tracks and new tunnels feasible. What he expressed to me as a difficulty turned into a near-impossibility in the report, in order to justify the $7 billion Penn Station South project.
But I want to focus on one particularly bad aspect of the proposal: the stopping patterns. The RPA is proposing three distinct stopping patterns on pp. 32-45, with three separate brands: Metro, in the city and some inner suburbs; Regional Express (RX), in the suburbs; and Trans-Regional Limited (TRL), providing intercity service to New Haven, Ronkonkoma, Philadelphia, and other major stations outside the built-up area. Even as the plan talks about the importance of making sure suburban trains serve urban stations in order to give them frequent service through overlay, the stopping patterns suggest the opposite.
The proposal involves trains from the suburbs expressing through most city stations (including the infill) even on two-track lines, like the Port Washington Branch. Metro trains would make all current stops plus additional infill to Bayside, and RX trains would only serve Willets Point, Flushing, and Bayside, and then run from Bayside to Port Washington. A similar pattern happens from Jamaica to Valley Stream, resulting in the Babylon, Long Beach, and Far Rockaway Branches all having to share a track pair. Moreover, the RX trains may themselves be divided into local and express trains, for example on the New Haven Line.
This is bad practice. On a two-track line, there’s no real reason to skip a handful of inner stations just to guarantee the outer ones express service. If anything, the need to schedule trains on the same tracks would lead to more fragile timetables, requiring more schedule padding. My analysis from 2.5 years ago found that the LIRR Main Line is padded 32% and the Babylon Branch is padded 19%: that is, the scheduled travel time on the Main Line (up to Ronkonkoma) is 32% more than the travel time imputed from line speed limits and current fleet acceleration performance. Patrick O’Hara, who the RPA study even quotes as a source elsewhere, investigated this issue separately, looking at best-case timetables, and found that some runs are padded 40-50%.
In Switzerland, trains are padded 7%, and I’m told that in Japan, after the Amagasaki accident showcased the safety problems of overly precise schedules, pads are about 5%. Express trains and locals mixed on the same line make it harder to maintain tight enough reliability for low schedule padding; this way, on an all-local line, trip times may match those of express trains on mixed lines, as they do in my analysis above. The best analogy is the RER B going to the north: the express trains are 4 minutes faster than the local trains, skipping 9 stops. The stop penalty on the RER B is higher, closer to 7 minutes over 9 stops, but the shared tracks with local trains (and with the RER D between Gare du Nord and Chatelet-Les Halles) means that there’s a fudge factor in the schedule, so it’s not possible to reliably do better than 4 minutes, and the trains end up visibly crawling on the mainline.
The reader familiar with technical transit advocacy in the Bay Area may interject, what about Caltrain? Clem Tillier has no trouble proposing timetables mixing local trains, express trains, and high-speed rail on the same track pair with timed overtakes, and a 7% pad. So why am I down on this concept in New York? The answer is line complexity. Caltrain is a simple two-track back-and-forth, and HSR is generally more punctual than legacy trains because it runs for long stretches on high-quality dedicated tracks, so it’s unlikely to introduce new variability to the line. In contrast, the RPA plan for regional rail in New York involves extensive branching, so that train schedules depend on trains elsewhere on the line. In this case, introducing more complexity through local/express sharing is likely to require more schedule padding, erasing the speed advantage.
In general, my questions to establish guidelines for where express trains are warranted are,
- How long is the line, measured in the number of stations? More stations encourage more express trains, because more stations can be skipped. In higher speed zones, stop penalties are higher, but at equal line length measured in km, higher speeds and fewer local stations reduce the benefit of express trains.
- How frequent are trains? At low frequency, local stations need more frequency, so express runs are less useful. At very high frequency, there may not be capacity for different stopping patterns unless the line has four tracks. On a two-track line, the optimum frequency for a local/express alternation is about 6-12 trains per hour, 3-6 local and 3-6 express, with a single mid-line overtake. Multiple overtakes on a single line are possible, but more fragile, so they are a bad idea except in special circumstances.
- What is the demand for travel? Express trains work best if there are a few distinguished stations at regular intervals, or else if the line is long and there is strong demand at the far end; if the inner stations are very strong then it’s more important to give them higher local frequency. When performing this analysis, it’s important to make sure station ridership levels reflect genuine demand rather than service. For example, Caltrain express stops have high ridership in large part because of their better service, not nearby density, as shown in Clem Tillier’s analysis. The LIRR Main Line has far more ridership at Mineola and Hicksville than the other stations on the trunk and also far more service, but Patrick explains that this is due to better highway access, so it’s genuine demand and not just a reflection of better service.
Caltrain needs express service because it has about 20 stations between San Francisco and San Jose, depending on the amount of infill and anti-infill desired; a target frequency of 8-10 peak trains per hour; and strong demand on the outer stations, especially for reverse-peak trips. In New York, none of the two-track lines meets the same standard. Some are too short, such as the Port Washington Branch. Others are too busy, such as the Harlem Line, Babylon Branch, and LIRR Main Line. Yet others have too much demand clustering in the inner stations, such as the Erie lines and the North Jersey Coast Line.
On four-track lines, it’s always easier to run express service. This doesn’t mean it should always be run: the upper New Haven Line is a strong candidate for relegating all commuter trains to the local tracks, making all stops, giving the express tracks to intercity trains. The Northeast Corridor Line in New Jersey is a dicey example: past Rahway there are four tracks, but intercity trains could run at very high speeds, making track sharing on the express tracks difficult. My service pattern map has express trains skipping Edison and Metuchen, but it’s just two stations, making it better to just run local beyond Rahway to clear the express tracks for high-speed rail.
It’s tempting to draw proposals involving intense metro-style regional rail service only serving the urban and inner-suburban stations; I’ve had to argue against such plans on some MBTA lines. The problem is that trains from the outer suburbs are still necessary and still going to pass through the inner suburbs, and in most cases they might as well stop at those stations, which need the frequency more than the outer suburbs need the few minutes of speedup.