Augmenting low-carbon sustainable cities using transit-linked mixed-use designs: A quasi-experimental regression of travel and emission outcomes

• We introduce TOD-MXDs – a novel hybrid design typology leveraging the strengths of TODs and MXDs. • TOD-MXDs remain rare in the U.S., with only 10.7 % of the 710 sampled developments fitting the criteria. • TOD-MXDs achieve 20 % lower VMT than MXDs and even fewer than comparable conventional designs. • TOD-MXDs generate about 19.7 % less CO₂ emissions compared to typical mixed-use developments. • Transit proximity (within a half-mile radius) matters for low-impact sustainable design outcomes. Cities today continue to struggle with the converging twin crises of rising vehicular air pollution and emission-intensive land use, prompting a renewed urgency for climate-smart urban designs such as mixed-use (MXDs) and transit-oriented developments (TODs). Yet, not all developments are designed to have a transit-focused orientation, and even if they are, individual lifestyle choices confound their true effects. This study investigates whether those MXDs situated near high-frequency transit ( a design typology we call Transit-Oriented Mixed-Use Developments (TOD-MXDs)) represent a more sustainable antidote to the environmental and mobility crises afflicting cities. Leveraging the largest geo-spatially harmonized database of individual-level and built environment characteristics across 36 diverse U.S. regions, we employ a mix of quasi-experimental design and advanced multivariate regression modeling to estimate travel characteristics and emissions outcomes. Results showed that although TOD-MXDs remain relatively scarce, they consistently outperform their non-transit-oriented counterparts, generating about 20 % less VMT, higher walking (87.6 %) and biking (83 %) trip shares, and significantly lower CO 2 e emissions, even after accounting for residential self-selection and the full suite of 7-D built environment variables. Furthermore, a unit increase in the presence of transit around mixed-use designs was associated with a ∼13.8 % reduction in VMT, suggesting that coupling land-use diversity with transit integration produces a synergistic effect that advances low-carbon and sustainable city outcomes. As conventional planning and policymakers strive for climate-resilient and healthy communities, this study makes a bold case: TOD-MXDs are not just better, they may be essential to the future of climate adaptation in cities through built-environment design.