I was on a packed Red Line train shortly after 6 p.m. [Monday] when a fight broke out between two passengers as the train was moving between Farragut North and Metro Center. As the two passengers fought near the forward end of the car, several passengers tried to find the emergency call button to call the train conductor.

 Apparently, the button was at the rear of the train car, but the train was so crowded it took some time for word to get to the passengers within reach of the call button. In the meantime, passengers in the center of the car, desperate to do something to get the attention of the train operator, opened the emergency box, which only has an emergency brake lever that stops the train, but no call button. A passenger pulled the lever, which stopped the train.A few moments later, the train operator, as if unaware of why the train stopped, asked passengers to stop leaning on the doors. About five tense minutes later — during which time a couple of good Samaritans kept the two combatants separated — two Metro police officers boarded the train and got it moving (after some struggle with the now-extended brake lever) to Metro Center.

— Isaiah J. Poole, Washington

Passengers can easily get confused about the purpose of the red boxes on either side of the central doors. They don’t control the brakes. Pulling the lever releases the central door so passengers can evacuate the car. Open that box only in an emergency, and on the instructions of the train operator after the train has stopped. Leaping from a moving train into a darkened tunnel is not an option.

The emergency door boxes are not a substitute for the intercoms. But on a crowded train, the intercoms are hard to get to at the ends of the cars, and sometimes — as we saw when train operators were inadvertently stopping with some rear cars still in tunnels — passengers don’t think about using them in time.

There’s a better setup on the newest cars: Call buttons and intercoms are in the middle of the cars as well as at the ends. And the boxes with the emergency door levers are colored beige, rather than red. The lettering says “Emergency Door Release.”

When the Red Line train’s lever was pulled by a rider in the fifth car on Monday, the train operator up front got an indication that there was a door problem. At the same time, Metro spokesman Steven Taubenkibel said, the train’s fail-safe system was bringing it to a stop. Transit police responded to the incident, located the fighters and removed them from the train at Metro Center, Taubenkibel said. They declined to press charges against each other.