The quiet carriage works, and nobody can quite explain why. There is no penalty. The conductor mentions it once, in a tone suggesting he does not expect to be involved further, and then walks through twice more without looking up. No fine has ever been issued on this line, as far as anybody knows. Yet on a full train, in a country not otherwise famous for its restraint, forty-two people will sit for three hours without a phone call. The enforcement, when it happens, is almost invisible. A man near the window answers a call in the fourth carriage; three people look at him, not aggressively, and one of them looks away again immediately, which is somehow the more effective gesture. He is off the phone in nine seconds, and he spends the next hour reading a newspaper he does not appear to be interested in. I have watched this several times and the timing is consistent. What makes it interesting is that it should not scale. A rule with no punishment ought to erode, one small violation at a time, as each person calculates that a single exception costs nothing. That is the standard account of how commons collapse, and it is usually right. Here it does not happen, and the reason appears to be that the cost is not paid to an institution. It is paid to the forty-one other people, who are present, who are visible, and who will be sitting there for the rest of the journey. I suspect this is also why the effect ends at the door. The same passengers stand up at the terminus and become instantly, comprehensively loud, and the platform is chaos within a minute. Nothing has been violated. The carriage has simply stopped existing, and with it the only thing that was ever holding anybody to anything.