Last week I was on the train and a non-English speaking fellow was having trouble with the rent-a-cop fare checker. (The passenger failed to beep his card before he got on the train.) The rent-a-cop gave up after a minute, gave the dude a warning ticket, and left.
I noticed that my seatmate had a newspaper with him. A quick glance at his newspaper and a few tries with
a translate site on my phone let me engage in 1-way communication with him. (My first guess was Vietnamese, but dur dur Vietnamese uses heavily accented Latin characters; his paper had ideogram-ish glyphs.) (I used Chinese(simplified) and that worked.)
I was able to communicate with him 1. what the security guy wanted and 2. what he (the passenger) should do in the future. About two hours later, I realized how to answer his last question: (No, you do not have to pay the $150 fine right now, but you might have to if you fail to "tap" your card in the future.)
I had a lot of pleased self-satisfaction at how I was able to help this guy. I thought, "In your face, you smug no-cell-phone people."