The current paper aims at examining ways to support sustainable modes in a metropolitan environment, as a means of enhancing accessibility and social equity. The study adopts a mix-method approach consisting of field observations, literature review and secondary data analysis. Through this approach, the research develops a method for reconceptualising urban car traffic arterials and provides a coherent plan for transforming them into multimodal corridors. The multimodal corridors are proposed based on their position in the street network, their connectivity properties, their urban characteristics, the existence of major public transport routes or dedicated cycling routes and their current street classification. Furthermore, the paper suggests design methods referring to each corridor category under the principles of sustainable mobility (e.g. cross-sections). The study area is the metropolitan area of Athens (AMA) in Greece. The implementation of the proposed interventions is expected to generate significant positive impacts such as the promotion of active modes and public transport, unification of the urban fabric, accessibility improvements, environmental protection and urban liveability benefits. The creation of multimodal corridors constitutes an alternative planning tool which prioritises walking, cycling and public transport. The method developed in this case study could be applied to other study areas with similar characteristics and may be a prototypical “roadmap” for policy-makers, planners and local communities, aiming to transform car-dominated corridors to multimodal ones.