Modelling carbon generated from individual urban travel activities: An empirical approach using the Lévy distribution

Understanding carbon generation from Individual Travel Activities (ITAs) requires moving beyond aggregate household or per-capita measures to examine frequency distributions across diverse set of trip characteristics. Yet, current research lacks a well-established empirical framework operating at a disaggregated level to profile the relationship between ITAs and carbon generation. Drawing on household travel survey data for South East Queensland, Australia, this study details a frequency-distribution modelling approach that employs the Lévy distribution to characterise how carbon generation varies across ITAs. The method enhances existing carbon estimation practices beyond traditional mean-based or aggregate approaches. A seven-parameter framework derived from normal-Lévy distribution coefficients captures the relationship between travel frequency and carbon generation, enabling systematic comparison across travel modes, purposes, and household locations. The model empirically derives carbon generation thresholds (2.88 kg CO 2 per trip) to distinguish between intra-urban and inter-city trips, replacing administratively-defined boundaries with a data-driven spatial delineation alternative. Results reveal that while 83.5 % of trips generate relatively low carbon emission (no more than 2.88 kg per trip), these frequent, low intensity intra-urban activities constitute the majority of total carbon generation, challenging the typical conventional focus on high-emission trip reduction. This frequency-distribution approach provides urban planners and policymakers with an empirical framework for quantifying carbon impacts at the ITA level through which tailored interventions can be designed to encourage a shift to lower-carbon alternatives. • The Lévy distribution can profile carbon generation from individual travel activities. • 80 % of trips generate 0.1–2.5 kg of carbon and contribute to 67.5 % of the total carbon. • The threshold of 2.88 kg can delineate intra-urban and inter-city travel activities. • Households located further from city centres generate more carbon per trip. • Work commuting trips generate more carbon than trips for all other purposes.