This paper examines everyday social interactions on public transport, focusing on acts of incivility observed along a busy inner-city bus route in Stockholm, the capital of Sweden. Using systematic observations with a fieldwork protocol, we adopt a mixed-methods approach, including logistic regression models to analyse these travel behaviours. The range of behaviours observed is broad and difficult to classify. Of 119 observed interactions, 83 instances were categorised as acts of incivility, not directed at one person but towards those travelling on the bus (‘diffuse incivility’), such as playing music loudly or disrupting exits. The regression model explains over half of the variation in observed transit incivility, with incivilities significantly more likely to occur on weekends and farther from the driver’s cabin. Targeted, context-specific measures, such as signage addressing group behaviours, can help prevent undesirable conduct and encourage acts of courtesy between travellers on buses.