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Why Are Some Letters Missing From NYC Subways?

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If you’ve ridden the New York City subway, you know that the different trains are often designated by letters of the alphabet (or numbers, but we’re not talking about those).

If you’ve ridden the New York City subway a lot, you know that some letters are missing. And it’s not the tail end of the alphabet, either. There’s an A, B and C train and there’s also a Z train. But there's no H train or Y train. There are several other skipped letters, too.

The explanation for the missing letters fall (mostly) into two categories.

Discontinued

H, K, T, V and W are all former trains that have been discontinued. In fact, an in-depth look at the history of the Metropolitan Transportation Authority (MTA) reveals regular recycling of letters as trains go in and out of use. But let’s look at each of the current letters getting snubbed.

H

Technically, the H train is still in use. It is the internal name for the Rockaway Park shuttle in Queens that connects with the A train to provide service to the western edge of the peninsula. After a few years without any designation on the map, the shuttle became known as the HH train in 1962. Over the next several decades, it was known as the E and then the CC train. In the 1980s, the MTA did away with double letter designation and the shuttle earned its H name. Eventually, however, all shuttles started bearing the grey S designation on maps. Since this would create internal confusion, the MTA continues to call the Rockaway Park shuttle the H train for their own purposes.

H made a public resurgence as the name of a free shuttle that took over service for a suspended portion of the A train in the aftermath of Hurricane Sandy in 2012. The letter was available as the storm had also knocked out service on the Rockaway Park Shuttle. When both the shuttle and the A train came back online by the summer of 2013, H slipped back into hiding.

K

The K train used to run on the same Eighth Avenue track that currently sports the A, C, E. It was the name given to the former AA train when the use of double letters was discontinued in 1985. The K train was essentially the opposite of the C. Both ran locally between 168th street and the World Trade Center, but while C train service covered rush hours, the K took on midday, nights, and weekends. The K last ran on December 10, 1988; the next day, C train service was expanded to include all hours.

T

T (and TT) used to be the name of what is now known as the D train. It was absorbed by the B train in the 1960s, which was replaced by the W train and ultimately the D train in the early 2000s. If you miss the T train, never fear: It is the future name of the Second Avenue Subway, which is expected to open its first phase in December 2016.

V

Longtime New Yorkers may remember both the introduction and the dissolution of the short-lived V train. It debuted in December 2001 to replace a rerouted F train, traveling between the Lower East Side in Manhattan and Queens. Unfortunately, limited service patterns—the V only ran weekdays from approximately 6:30 a.m. to midnight—and budget cuts doomed the V train. In June 2010, it was merged with the M train and dropped the V designation.

W

Another short-lived, late-alphabet train, W debuted in 2001 to account for construction on the Manhattan Bridge tracks that disrupted the B train. During nearly nine years in use, its service area changed several times, going all the way to Coney Island to start, then eventually losing the Brooklyn borough altogether. In Manhattan, W traveled along the Broadway line that we now think of as the N, Q, R train, eventually getting absorbed into those lines in 2010 as a result of financial shortcomings.

Potential Confusion

The letters I and O were never used for trains because of their visual similarities to the numbers 0 and 1 and the use of both alphabetical and numerical designations in the New York Subway system. 

U and Y were eliminated from consideration because they are homonyms with actual words—namely, “you” and “why.” Apparently, the founders of what is now the MTA did not find the potential for “Who’s on First”-style confusion to be nearly as humorous as Abbott and Costello did.

The Problem with P

That leaves all the letters accounted for except P. There are several stories of almost-P trains. It was the intended name for the final leg of the Culver service (now the F line) into Manhattan that was scrapped in favor of a shuttle (labeled S as all shuttles are) at the last minute. It was also the name given to a specialty train designed to work around the 1992 potential Amtrak strike. Congress intervened at the last moment and no such emergency service was necessary. The P then stood for the incapacitated Penn Station. However, neither of these instances explain why it was never used for any new trains between the creation of the Culver shuttle and the 1992 near-strike. And so it is fun, if not entirely likely, to consider the theory that the P homonym was simply too immature for polite commuter conversation.

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Big Questions
What Causes Sinkholes?
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Mark Ralston/AFP/Getty Images

This week, a sinkhole opened up on the White House lawn—likely the result of excess rainfall on the "legitimate swamp" surrounding the storied building, a geologist told The New York Times. While the event had some suggesting we call for Buffy's help, sinkholes are pretty common. In the past few days alone, cavernous maws in the earth have appeared in Maryland, North Carolina, Tennessee, and of course Florida, home to more sinkholes than any other state.

Sinkholes have gulped down suburban homes, cars, and entire fields in the past. How does the ground just open up like that?

Sinkholes are a simple matter of cause and effect. Urban sinkholes may be directly traced to underground water main breaks or collapsed sewer pipelines, into which city sidewalks crumple in the absence of any structural support. In more rural areas, such catastrophes might be attributed to abandoned mine shafts or salt caverns that can't take the weight anymore. These types of sinkholes are heavily influenced by human action, but most sinkholes are unpredictable, inevitable natural occurrences.

Florida is so prone to sinkholes because it has the misfortune of being built upon a foundation of limestone—solid rock, but the kind that is easily dissolved by acidic rain or groundwater. The karst process, in which the mildly acidic water wears away at fractures in the limestone, leaves empty space where there used to be stone, and even the residue is washed away. Any loose soil, grass, or—for example—luxury condominiums perched atop the hole in the ground aren't left with much support. Just as a house built on a weak foundation is more likely to collapse, the same is true of the ground itself. Gravity eventually takes its toll, aided by natural erosion, and so the hole begins to sink.

About 10 percent of the world's landscape is composed of karst regions. Despite being common, sinkholes' unforeseeable nature serves as proof that the ground beneath our feet may not be as solid as we think.

A version of this story originally ran in 2014.

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Big Questions
How Are Speed Limits Set?
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When driving down a road where speed limits are oppressively low, or high enough to let drivers get away with reckless behavior, it's easy to blame the government for getting it wrong. But you and your fellow drivers play a bigger a role in determining speed limits than you might think.

Before cities can come up with speed limit figures, they first need to look at how fast motorists drive down certain roads when there are no limitations. According to The Sacramento Bee, officials conduct speed surveys on two types of roads: arterial roads (typically four-lane highways) and collector streets (two-lane roads connecting residential areas to arterials). Once the data has been collected, they toss out the fastest 15 percent of drivers. The thinking is that this group is probably going faster than what's safe and isn't representative of the average driver. The sweet spot, according to the state, is the 85th percentile: Drivers in this group are thought to occupy the Goldilocks zone of safety and efficiency.

Officials use whatever speed falls in the 85th percentile to set limits for that street, but they do have some wiggle room. If the average speed is 33 mph, for example, they’d normally round up to 35 or down to 30 to reach the nearest 5-mph increment. Whether they decide to make the number higher or lower depends on other information they know about that area. If there’s a risky turn, they might decide to round down and keep drivers on the slow side.

A road’s crash rate also comes into play: If the number of collisions per million miles traveled for that stretch of road is higher than average, officials might lower the speed limit regardless of the 85th percentile rule. Roads that have a history of accidents might also warrant a special signal or sign to reinforce the new speed limit.

For other types of roads, setting speed limits is more of a cut-and-dry process. Streets that run through school zones, business districts, and residential areas are all assigned standard speed limits that are much lower than what drivers might hit if given free rein.

Have you got a Big Question you'd like us to answer? If so, let us know by emailing us at bigquestions@mentalfloss.com.

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