Public behavior norms are the shared contract that lets millions of strangers coexist in tight spaces, and every country writes that contract a little differently. The common core is recognizable everywhere: queue fairly, keep noise down in transport and residential areas, respect personal space, keep shared spaces clean, give up seats to those who need them, and follow the local rhythm of quiet hours. Where countries differ is intensity, silence on trains is near-sacred in some places and irrelevant in others, and in specifics like jaywalking, eating in public, littering fines, or public displays of affection.
What makes these norms powerful is that they are largely self-enforced. Compliance is maintained by social expectation rather than police, which is exactly why violating them marks you as an outsider faster than any accent does. Locals rarely confront offenders; they just quietly withdraw goodwill.