Participatory Agent-Based Scenario Development for Mid-Sized Cities: Evaluating Housing and Sustainable Mobility Interactions

• Participatory ILUT modelling applied in a mid-sized North American city • Four-unit zoning plus parking limits reduce car dependence most • Agent-based model captures spatial and income travel heterogeneity • Scenario design co-developed with planners for policy relevance . This study explores the interplay between housing supply strategies, specifically greenfield and infill developments, and long-term changes in car ownership, travel mode choices, and vehicle/passenger kilometres travelled in the context of mid-sized North American cities. The City of Moncton serves as a representative case study, having recently experienced rapid internal and international migration. Particular focus is given to the emerging four-unit zoning strategy, currently being deployed in several Canadian provinces, as a means to address rising housing demand. An agent-based integrated land use and transportation (ILUT) modelling framework is applied to project population and behavioural dynamics from 2021 to 2046 under multiple land use and housing development scenarios. These scenarios were co-produced through an iterative collaborative process involving practising planners and engineers from the City of Moncton and the DalTRAC research group. The ILUT framework was developed using the 2023 CanTRAC survey data through calibration of discrete choice and heuristic behavioural models, with further validation of model outputs against the 2016 and 2021 Canadian Census data. Validation results indicated close agreement, with mean absolute error below 3% and root mean square error below 5%. Simulation outcomes revealed that while infill development alone does not sufficiently reduce car dependency, the combination of four-unit zoning with residential parking restrictions yields a significant reduction in car ownership and fosters a shift toward active modes of travel. These findings offer actionable insights for policymakers and planners aiming to shape sustainable mobility in rapidly growing mid-sized cities.