Triboro Rx-ing

Let us consider Triboro Rx. Transit pundits have been floating it for quite a long time — it was already around when I first started chatting about transportation stuff that was over my head, the better part of a decade ago — and the Regional Plan Association returns to it on occasion.

It is an excellent idea, on paper. It uses the underutilized LIRR Bay Ridge Branch and the Hell Gate Bridge to provide service between Brooklyn, Queens, and the Bronx (hence Triboro Regional express). While the Bronx end isn’t set in stone — I’ve seen maps terminating it at Hunts Point, Co-Op City, and Yankee Stadium — it’s generally agreed that it would be at a transfer point with another line.

Similar services exist on many other mass transit systems around the world — perhaps the best-known examples are London’s Circle Line and Moscow’s Koltsevaya. These types of lines are collector/distributor lines, bypassing the city center in favor of transfers to other services that reach it. In cities with high uniform density — like New York’s outer boroughs — such services can achieve high ridership, given adequate service. (Indeed, the lack of adequate service is often considered the G Train’s Achilles heel.)

However, that said, Triboro Rx suffers a strange and tricksy flaw: It may not be adequately futureproofed.

A Reaction to Present Conditions


Triboro RX is one of those only-in-New-York kinds of proposals. It takes an old, disused freight spur and part of an underutilized rail bridge and converts it into heavy rail. Every Bronx alignment uses rail easements exclusively: the Yankee Stadium route follows an old freight spur connecting the Harlem Line with Hunts Point; the Hunts Point and Co-Op City routes would have the subway run parallel to the Northeast Corridor.

This is feasible because existing traffic is light: most Bay Ridge traffic (if it exists) would connect to the carfloat to the Oak Island yard, and while the Hell Gate bridge is the only fixed-link freight rail access to Long Island, there is just not that much freight traffic to and from the island. It’s actually analogous to South Jersey and the Delmarva Peninsula in this way — a quiet network of old spurs; only on Long Island, most of them are still maintained for commuter service.

The heaviest current user is Amtrak across the Hell Gate. Amtrak is currently the only passenger operator across Hell Gate, but it does not need much in the way of slots, and curvature related to the approaches limits Acela speed. So, from the perspective of the current network, Triboro Rx is an all-around win-win — intercity trains do not amount to that many tph, allowing Hell Gate to have a 2-2 heavy rail-intercity rail split, and freight traffic is so light it amounts to night movements across the bridge and leaving a single free track for carfloat services along the Bay Ridge branch, which may not even need to directly connect into the Hell Gate approach Triboro Rx intends to use. From this perspective, then, Triboro Rx offers an excellent reuse of obsolescent railroad facilities.

But What about the Future?

Things, however, are not so simple. There are two major plans — already in motion — that affect the Triboro Rx ROW. The MTA has proposed running New Haven trains down the Hell Gate Line into Penn Station, and at the other end of the line, the Port Authority is advancing a plan to bore a trans-Hudson tunnel between the Greenville Yard and Bay Ridge. While both, in isolation, may be able to co-exist with Triboro Rx, my contention is that there may not be enough capacity across the Hell Gate Bridge proper to support both Triboro Rx and future service paradigms these other proposals will engender.

Penn Station Access


The MTA’s Penn Station Access plan has two arms: an extension of the Hudson Line into Penn Station from the west, and one of the New Haven Line from the east. Combined with the LIRR’s East Side Access project connecting directly to Grand Central, PSA will allow most commuter rail lines heading into Midtown to terminate at either of the main commuter rail terminals. It also provides new commuter rail stops in Bronx and on the Upper West Side.

The upshot of PSA is that more slots will be needed across Hell Gate. Unlike Amtrak, which we can see from this timetable currently runs 4 tph across Hell Gate (i.e. hourly Acela and Northeast Regional runs), the New Haven Line currently runs ~25 tph into Grand Central at its AM peak. This demand is also asymmetrically loaded; 4/5 (80%) of the runs are inbound during this peak.

From these characteristics, we can extrapolate how much capacity PSA needs on the Hell Gate Line, given an assumption of service provided. For example, if PSA were to perfectly duplicate the Grand Central schedule, 22 inbound slots across Hell Gate in the 8 AM hour are needed — this translates to a train just under once every 3 minutes!

As it is, however, it is likely PSA will result not in perfect duplication, but a major percentage of Grand Central service. At approximately 75% of Grand Central service, PSA would run 15 inbound and 3 outbound trains during the AM peak hour; this translates into demand for 17 inbound and 5 outbound slots across Hell Gate.*

The question then becomes how much capacity the signalling system can handle. If it can handle 20 tph (i.e. block clearance in 3 minutes) per track, then this service paradigm is just able to be handled on two tracks; if, on the other hand, it can only handle 15 tph (i.e. block clearance in 4 minutes) per track, then three tracks are required across Hell Gate to handle this service, as outbound services are very much frequent enough to demand a dedicated track.

That leaves space for just one track for Triboro Rx, immediately creating a chokepoint that cripples the line’s ability to provide adequate service to the Bronx. And this, in its turn, shows us what the key razor is: Triboro Rx must have two tracks across Hell Gate to be viable past Astoria. If it can’t, then it’s really just a “Duoboro Rx”.

…And the Freight


The other major Triboro Rx obstacle is the Cross-Harbor Rail Tunnel, which is intended to relieve trucking congestion across the Hudson’s other crossings, as well as provide a solution to the circuitous nature of freight rail within the New York metro. Cross-Harbor depends on the Bay Ridge branch, using it to access the Lower Montauk Branch at Bushwick Junction and continue to a transshipment facility at West Maspeth.

Generally, a minimum three tracks will be needed all the way down Bay Ridge from Sunnyside Junction: two for Triboro Rx and one for freight. As Hell Gate is the only freight fixed link between Long Island and the outside world, this is a design constraint that must be built around. Brief interlining segments are, however, available with the Canarsie Line (L) between New Lots and Wilson avenues, and with the Sea Beach Line (N) west of New Utrecht Avenue — these interlines suggest that Triboro Rx needs to be built to B Division standards.

However, Cross-Harbor provides an excellent opportunity for restructuring freight traffic patterns in the New York area. A long-term result of the connection made may well be that traffic to Providence & Worcester destinations in southwestern Connecticut originates in Greenville Yard, rather than the connection with CSX’s Boston & Albany line the railroad currently uses. This, in its turn, suggests a need for freight slots across Hell Gate.

Underutilized Today, Overutilized Tomorrow?


In our investigation of Triboro Rx’s viability from a network perspective, we’ve discovered something interesting about the Hell Gate Bridge: while it is a quiet and underutilized span today — seeing about 4 Amtrak tph and whatever interchange turns the New York & Atlantic, Long Island’s sole freight operator, deems necessary — plans for its tracks pull it in four directions, of which three are mutually incompatible.

This is, in a way, prefigured by prewar service patterns. The New Haven Railroad had electrified the entire line from Hell Gate to Bay Ridge because the carfloat there was its primary interchange with the Pennsylvania Railroad — as well as between the Pennsylvania and Long Island railroads. Even though the New Haven had always run its commuter trains into Grand Central (its intercity trains went to Penn Station), the Hell Gate line would have been consistently busy with freight traffic.

And this is the biggest rub for Triboro Rx. Under conditions where the PSA and Cross-Harbor connections are built out, all four tracks would be claimed: three for Amtrak and Metro-North, and one for the freight railroads, making use of Conrail’s Greenville Yard as an origin point for traffic throughout the region. There isn’t enough space space for Triboro Rx, not unless an addition to the span were built … or a bypass tunnel. Neither of which does wonders for the cost-effectiveness of Triboro Rx.

So — in conclusion, I would venture to say that Bay Ridge = Good, but Hell Gate = Bad for Triboro Rx. Relying on capacity for Hell Gate to be there, when there are enough asks embedded within existing proposals to suggest it, well, won’t is perhaps the plan’s biggest downfall. Without connecting to the Bronx, Triboro Rx looks rather like a further-afield version of the G Train. However, there is a solution to this.

Futureproofing Triboro Rx: Using M8’s?


I’ve been analyzing Triboro Rx so far as a B Division subway line. This means it can interline with other B Division routes, but not with mainline rail. But we can clearly see that Hell Gate’s other future capacity demands are all caused by mainline rail. And we can also see that every Triboro Rx proposal has it running in or alongside active mainline railroads. It then follows that the solution to the potential capacity issues I’ve brought up so far is to make it, well, a mainline railroad itself.

While building to mainline standard rather than heavy rail standard is, well, heavier and more expensive, it’s worth noting that this corridor will be a freight railroad end-to-end should Cross-Harbor come to fruition, and that two all-purpose tracks with off-peak freight use is a much more efficient distribution of service. It’s also worth pointing out that this alignment was historically electrified under the old Northeastern catenary standard the Pennsylvania developed (12.5 kV 25 Hz AC).

While the downside of this approach is that it is impossible to extend Triboro Rx via the subway system, the upside — Triboro Rx is essentially inserted among other improvements slated in the mainline network — is hard to ignore. And M8 stock is able to pick up every type of traction power (12 kV 60 Hz AC; 25 kV 60 Hz AC; 750 V DC) in use on the island — something the MNRR and LIRR M7’s can’t.

This is not a perfect solution, however: one issue that needs to be explored is whether double-stacks and high-level platforms under wire can be made to be compatible. That does not mean that Triboro Rx is not worth looking at, and tinkering with, in order to coexist with the rest of the city and region’s transportation network and help handle their various needs.

NOTE: I was made aware of the Regional Plan Association’s Triboro Rx policy brief via Second Avenue Sagas the same day this post originally ran. In it, the RPA also points out the freight issue I brought up — although not the Hell Gate issue. In any event, using MNRR/LIRR equipment for Triboro Rx seems to be the optimal solution. The policy brief also suggests extending Triboro Rx to Staten Island — further extending it down the SIR would be a match made in heaven.


* Note that another way of looking at this is that PSA will siphon off a significant percentage of New Haven Line runs currently into Grand Central, whose main approach is very much overcrowded. Were PSA to siphon off 1/3 of the NH’s service, this would approximate to an 8/2 split, leading to 14 trains across Hell Gate during the peak hour with a 10/4 split. It is fair to point out that a 2-track railroad should be able to support this service paradigm, and it is also fair to point out that the whole point of PSA is to alleviate overcrowding in Grand Central’s throat by diverting some percentage of Hudson and New Haven line trains to Penn Station instead.

However, my sense is that the end result of ESA and PSA is that the system will rebalance to the point where every available throat will, once again, be congested.

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