Urban mobility and carbon emissions: Decoding the influence of sociodemographic factors, trip-level built environment, and travel behaviour of workers in three UK cities

Quantifying how individual-level travel patterns intersect with built environment features and sociodemographic characteristics is essential for addressing transportation-related CO₂ emissions. Existing evidence is predominantly based on aggregated individual and/or area-based data, neglecting important drivers of emissions at the trip level and variations by individual characteristics, including employment types. GPS-tracked mobility patterns from a random sample of 587 workers in three UK cities (Brighton and Hove, Leeds, and Birmingham) are analysed to estimate CO₂ emissions at the trip-level and person-level, accounting for multi-modal travel. Walkability and public transport availability at trip origins is associated with reduced emissions at the trip level but not overall individual emissions. Employing latent class analysis, participants were grouped based on multiple sociodemographic characteristics. Women with no access to a car were identified as low emitters, while individuals with access to a car as high emitters, regardless of gender and education level. These findings reinforce the need for policy frameworks that extend beyond traditional single-location strategies. Enhancing walkability and public transit connectivity in key activity hubs such as commercial, leisure, and other high-traffic areas, alongside incentives for behaviour change, offers significant potential to reduce transportation CO₂ emissions. Moreover, as dynamic population shifts and evolving travel patterns weaken the effectiveness of monocentric urban structures, our findings suggest that transitioning toward a polycentric model can be a more effective strategy for lowering transport-related CO₂ emissions. By emphasizing this broader spatial reach, urban planners and policymakers can better tailor interventions to distinct population segments, effectively supporting low-carbon travel and advancing sustainable urban mobility goals.