Even though every subway car is equipped with an emergency brake, the Metropolitan Transportation Authority says the brakes shouldn't be used during most emergencies. If there's a crime, fire, or medical emergency, straphangers shouldn't yank on the emergency brake cord. In fact, the first instruction on the "Emergency Instructions" placard tells commuters: "Do not pull the emergency cord." So, what's it good for?

According to the Times, straphangers should pull the brake if "someone gets caught between the train's closing doors, or between subway cars, and is about to be dragged to an unenviable fate." In other circumstances, pulling the cord could make it harder for help to arrive. That's what happened on a D train last November when a straphanger fatally stabbed another commuter and frightened passengers pulled the brake. The agency has told Gothamist that when a straphanger pulls the cord, it brings the train to an immediate stop using compressed-air brakes. The train crew must notify a control center, which in turn alerts police. The NYPD then advises the control center on how to respond, and that message is relayed to the train crew. It can take between 5 and 15 minutes for the crew to reset the braking function and get the train moving again.

Commuters pull the emergency brake about 1,000 times per year when there is no clear emergency. In 2009, the agency recorded 15 instances in which straphangers pulled the cord to respond to an emergency, like a sick rider, the paper notes. Some subway riders, like Brooklyn resident Zev David Deans, said the agency should more clearly outline when straphangers should, and shouldn't, use the emergency brake. "They could put it in big letters — 'Pull in case of ...' — and then the few reasons why," he said. "If it just says 'emergency,' you're going to pull it for any reason." An MTA NYC Transit spokesman said the current instructions are more than sufficient: "We think that it is clear."