Dear Helena,

I recently returned from New York, where I encountered multiple instances of food consumption on mass transit. If it wasn’t so hot, I’m sure the odor of the McDonald’s Double Cheeseburger wouldn’t have been so foul, and the assortment of fries that fell to the ground, collecting black shoe prints, wouldn’t have been so foul—but I about threw up.

People in New York eat a lot of granola/energy bars, little bites from Ziploc bags—the worst offenders are the homeless who somehow manage to lump a five-course meal into a dirty plastic bag that inevitably leaks onto the seat or falls to the floor and, as the bus climbs a hill, makes a beeline toward your feet.

What is the etiquette of eating on public transit? When is it acceptable? I ate an apple on the bus, and it was a particularly quiet bus, so it felt a little like a spectacle … but I enjoyed it. —Jaded Commuter

Dear Jaded Commuter,

Eating on a train or bus can be messy and malodorous, which is why many public transit systems prohibit it. Jack Taylor, an associate creative director in Brooklyn, New York, says of the subway: “I don’t mind smelling a pungent curry in the right context, like an Indian restaurant, but not on my way home, mixing with other people’s body odor.” Worse, eating on a moving vehicle can be hazardous. Taylor says he gets nervous when he sees someone board a crowded car clutching a morning coffee. “You’re just staring at that coffee cup, wondering when the subway brakes are going to hit and the coffee is going to go flying all over you.”

Subway dining is bad for the diner as well as for other passengers. You’ve been touching germ-infested poles, turnstiles, and armrests, so unless you have an antiseptic wipe you’ll be eating with dirty hands.

Moreover, eating is one of the more reliable pleasures in life, and when you do so you should pay attention. The French traditionally linger over meals and would not dream of spoiling their food by eating it on le Métro. Fabrice Habelski, a wine broker originally from the suburbs of Paris, recoils in horror at the very idea: “It is illegal and unconscionable.” He says he has never seen anyone do it, “not even peanuts out of a bag.”

It’s sad if you can’t set aside time to enjoy a meal, even if it’s only 10 or 15 minutes. You need not always have a cloth napkin, but you should at the very least have a stationary surface on which to rest your food. (When you’re being jolted and jostled, your lap doesn’t make much of a table.) And while you’re eating, you shouldn’t be worried about missing your stop.

There are two exceptions to the no-subway-dining rule. Not everyone has the time and the place to enjoy a meal. Obviously, it’s OK to eat on a train or bus if you don’t have much of a choice. For instance, a homeless person might prefer to dine in a subway carriage rather than on a freezing park bench. And, as Taylor points out, many chronic subway diners have “two or three jobs” through financial necessity, and genuinely have no other time to eat.

The other exception to the rule is when your need is urgent. It’s OK to scarf some trail mix if you’re diabetic and will otherwise lapse into a coma. And it’s OK to eat a banana if you’re on your way to a job interview and your low blood sugar might make you flub it. What is the perfect subway snack for such occasions? As you have observed, many New Yorkers have already discovered it: an energy or granola bar. It’s neat, and odorless.

Table Manners appears every Wednesday. Have a Table Manners question? Email Helena.

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