Measuring and visualising ‘familiar strangers’ among transit riders: An exploratory study of Brisbane, Australia

Public transport with high levels of patronage is the cornerstone of a sustainable city. Passengers' feelings of safety shapes an individuals' decision to utilise public transport that are informed in large part by the other people with which the transit stations and public transit trips are shared. Some of these people are unknown to us but considered – familiar strangers – in that we visually recognise the individuals but have never spoken to them. Our empirical understanding of this subtle yet important social phenomena known to impact sense of community, place attachment and feelings of safety remain in their infancy but with emergence of disaggregate sources of big data bourne from smart card technologies there exists new opportunities to measure and visualise potential familiar strangers in transit networks. The aim of the current study is to develop a new measurement framework that moves beyond existing work that measures familiar strangers via a single volumetric measure and introduce a suite of metrics capturing the full scope of the social phenomena within a transit network. Our measurement framework and associated metrics are operationalised using smart card data from Brisbane, Australia. Results hold implications for policy and planning, and it is hoped that the framework will be redeployed across other situational and cultural contexts forming a growing set of comparative studies.