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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.


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.


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.


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 (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.


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.


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
Can You Really Go Blind Staring at a Solar Eclipse?
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A total solar eclipse will cut a path of totality across the United States on August 21, and eclipse mania is gripping the country. Should the wide-eyed and unprotected hazard a peek at this rare phenomenon?

NASA doesn't advise it. The truth is, a quick glance at a solar eclipse won't leave you blind. But you're not doing your peepers any favors. As NASA explains, even when 99 percent of the sun's surface is covered, the 1 percent that sneaks out around the edges is enough to damage the rod and cone cells in your retinas. As this light and radiation flood into the eye, the retina becomes trapped in a sort of solar cooker that scorches its tissue. And because your retinas don't have any pain receptors, your eyes have no way of warning you to stop.

The good news for astronomy enthusiasts is that there are ways to safely view a solar eclipse. A pair of NASA-approved eclipse glasses will block the retina-frying rays, but sunglasses or any other kind of smoked lenses cannot. (The editors at, an eclipse watchers' fan site, put shades in the "eye suicide" category.) NASA also suggests watching the eclipse indirectly through a pinhole projector, or through binoculars or a telescope fitted with special solar filters.

While it's safe to take a quick, unfiltered peek at the sun in the brief totality of a total solar eclipse, doing so during the partial phases—when the Moon is not completely covering the Sun—is much riskier.


NASA's website tackled this question. Their short answer: that could ruin their lives.

"A student who heeds warnings from teachers and other authorities not to view the eclipse because of the danger to vision, and learns later that other students did see it safely, may feel cheated out of the experience. Having now learned that the authority figure was wrong on one occasion, how is this student going to react when other health-related advice about drugs, alcohol, AIDS, or smoking is given[?]"

This story was originally published in 2012.

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Big Questions
If Beer and Bread Use Almost the Exact Same Ingredients, Why Isn't Bread Alcoholic?
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If beer and bread use almost the exact same ingredients (minus hops) why isn't bread alcoholic?

Josh Velson:

All yeast breads contain some amount of alcohol. Have you ever smelled a rising loaf of bread or, better yet, smelled the air underneath dough that has been covered while rising? It smells really boozy. And that sweet smell that fresh-baked bread has under the yeast and nutty Maillard reaction notes? Alcohol.

However, during the baking process, most of the alcohol in the dough evaporates into the atmosphere. This is basically the same thing that happens to much of the water in the dough as well. And it’s long been known that bread contains residual alcohol—up to 1.9 percent of it. In the 1920s, the American Chemical Society even had a set of experimenters report on it.

Anecdotally, I’ve also accidentally made really boozy bread by letting a white bread dough rise for too long. The end result was that not enough of the alcohol boiled off, and the darned thing tasted like alcohol. You can also taste alcohol in the doughy bits of underbaked white bread, which I categorically do not recommend you try making.

Putting on my industrial biochemistry hat here, many [people] claim that alcohol is only the product of a “starvation process” on yeast once they run out of oxygen. That’s wrong.

The most common brewers and bread yeasts, of the Saccharomyces genus (and some of the Brettanomyces genus, also used to produce beer), will produce alcohol in both a beer wort
and in bread dough immediately, regardless of aeration. This is actually a surprising result, as it runs counter to what is most efficient for the cell (and, incidentally, the simplistic version of yeast biology that is often taught to home brewers). The expectation would be that the cell would perform aerobic respiration (full conversion of sugar and oxygen to carbon dioxide and water) until oxygen runs out, and only then revert to alcoholic fermentation, which runs without oxygen but produces less energy.

Instead, if a Saccharomyces yeast finds itself in a high-sugar environment, regardless of the presence of air it will start producing ethanol, shunting sugar into the anaerobic respiration pathway while still running the aerobic process in parallel. This phenomenon is known as the Crabtree effect, and is speculated to be an adaptation to suppress competing organisms
in the high-sugar environment because ethanol has antiseptic properties that yeasts are tolerant to but competitors are not. It’s a quirk of Saccharomyces biology that you basically only learn about if you spent a long time doing way too much yeast cell culture … like me.

This post originally appeared on Quora. Click here to view.


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