Time to Revisit Overhead Electrification under Park Avenue?
One of the commonly cited excuses to not build the tunnel needed for through running between the ex-New York Central network feeding into Grand Central and the ex-Pennsylvania/Jersey Central/Lackawanna network feeding Penn Station is the need for trains to handle both third rail and overhead wire. I have written on this blog that cars that do so and can fit every single New York-area regional rail tunnel have existed for decades. On top of that, recent discussion with a knowledgeable consultant suggests to me that modern overhead line equipment (OLE) could potentially fit into the Park Avenue tunnels with today’s trains.
Per an old Congressional hearing transcript, the distance from the ceiling of the Park Avenue tunnel to the top of rail (ToR) is 15’ 1”. Today, the tallest train that runs in it measures 14’ 6” above ToR. That is also just about the maximum train height the North River Tunnels, which have had overhead wire since the 1930s, permit. That means the total space from the top of the train to the structure for an overhead current carrier is 7” or 178 mm. In the UK, for standard 25 kV AC electrification, special permission allows 150 mm of clearance above the contact wire to structure, and the minimum clearance is 200 mm from the contact wire to the train envelope, for a total of 350 mm. However, per a presentation made by Network Rail engineers, new technology can potentially reduce both the required the wire-to-structure and train-to-wire gap:
Surge arresters can reduce wire-to-structure clearances to 80 mm or even lower if combined with a contact wire cover and insulated paint.
Combining surge arresters with shaped metal plates and insulated pantographs can reduce the clearance between the wire and the train roof to as low as 60 mm.
Combined, these technologies could potentially allow electrification with as little as 140 mm or 5.5“ between the train roof and the structure. Furthermore, it is my understanding that the Park Avenue tunnel has ballasted track. Direct fixation track could allow the rail to sit several inches lower in the tunnel, which per an old newspaper clipping is 16’ 8” from the floor to the ceiling. Lowering the track in a tunnel has ample precedent, and I do not know about lowering the tunnel floor itself.
To my eye, as a curious outsider, it seems the technology to equip the Park Avenue tunnel with overhead wire is at least mostly there. However, for the 63rd Street tunnel, it may still be the case that it is cheaper to stick third rail shoes on cars rather than fit the tunnel—the tightest regional rail tunnel in New York—with overhead equipment. In that scenario, the business case for converting Park Avenue to overhead electrification is reduced, since New York would need at least some cars to use both third rail and wire anyway. It must be said that, to my knowledge, the aforementioned technology has not been widely applied. The closer the clearances are, the higher the risks of a tripping event. Installation of any overhead system will take months of disruption.
Having mentioned several caveats, the answer to whether the ex-New York Central network can be converted to overhead electrification is probably yes. Switches in the Grand Central station throat used to have overhead contact strips powered with DC to prevent locomotives from losing power, and most of the platform tracks seem to have enough room for overhead equipment. Compared to Grand Central, whatever track lowering or platform height adjustments are required in the Bronx, Westchester and upstate—where the clearance from structures to ToR is supposedly at least 16’—should be easy.
While New York can use flexible rolling stock in the medium term, modern non-metro rail systems use OLE powered with alternating current for good reasons. It permits higher speeds and requires fewer substations and less power than third rail or wire powered with direct current. OLE is almost certainly safer for passengers and workers than third rail. For example, in the recent Katonah Harlem Line crash, the third rail pierced a train car, igniting a fire. I do not know of any OLE failures that have done similar damage to the inside of a train car. Besides the wire already on the New Haven Line, the Hudson Line feeds into Penn Station. At Amtrak-level electrification costs, which are some of the highest in the world, the entire Harlem Line to Wassaic, Hudson Line to Albany, and Empire Connection would cost around $2 billion to wire. Electric trains would significantly cut travel times for outer Harlem and Hudson riders and intercity riders to Albany and beyond—even with an engine change. Plus cars that only have to use overhead wire likely cost at least somewhat less to acquire and maintain than dual-power stock like the M8 or the Class 700.
In the short to medium term, conversion of the ex-Pennsylvania electrification from the original frequency of 25 Hz to the modern North American standard of 60 Hz would cut out substantial amounts of custom equipment and cut in half the weight of transformer that trains have to carry. Unlike an increase of voltage from 12 kV to 25 kV, this frequency change should not require increasing clearances or replacing OLE components. The change would allow the M8—whose transformer is large enough for 60 Hz but not 25 Hz—to run to New Jersey and beyond without using third rail west of the 60 Hz/25 Hz transition in Queens. As a second-tier project, standardized electrification of New York regional rail is likely to bring some benefit, and OLE in the Park Avenue and 63rd Street tunnels is at least worth a fresh look.