Beyond downtown: How restricted access policies shift pollution rather than eliminate it

Urban traffic restriction policies aim to reduce congestion and emissions, yet their unintended effects on freight transport are often overlooked. This study employs activity-based travel demand modelling, embedded in an agent-based simulation, to evaluate the impact of a restricted access policy on freight operations, on-road emissions, and life-cycle carbon emissions. Findings reveal that delivery vans faced increased detours and inefficiencies, resulting in higher local and global emissions. While cargo bikes reduce local air pollutants, their limited efficiency and notable particulate and carbon emissions offset some of their benefits. Crucially, the policy shifted pollution from city centres to peripheral zones, highlighting spatial inequities in air quality. These results underscore a critical trade-off: improvements in local air quality may be achieved at the expense of increased ${\text{CO}}_2$ emissions, contributing to the more widespread environmental harm of global warming. The study advocates for more holistic, equity-aware policy design.