As cities have grown more dispersed and auto-oriented, demand for travel has become increasingly difficult to meet via public transit. Delivering high-quality bus service in this challenging environment has recently brought attention to bus network design. Commonly, bus networks are designed with a door-to-door approach, which often entails a circuitous route design leading to slow and infrequent service, especially in the suburbs. Alternatively, high-frequency transfer based networks have been promoted as the optimal network design for ridership, experience and operational efficiency. For cities wishing to adopt such a network design, there is presently no comprehensive, easy to follow methodology for transitioning to this network model. This study presents a methodology to guide transport professionals through the process of redesigning an existing door-to-door network to a transfer-based high-frequency service, using Longueuil, Quebec, as a case study. A variety of data sources that capture regional travel behaviour and network performance are overlaid using a GIS-based grid-cell model, to identify priority bus corridors, which is followed by a network redesign that is constrained by the existing number of buses. Changes in accessibility to jobs are used to evaluate the benefits of the proposed network. This methodology provides transit professionals with a flexible and reproducible guide for designing a transfer-based network, while ensuring that such a network overhaul maximizes the number of opportunities that residents can access by transit and does not add an additional burden to an agency’s operating budget or users in terms of total travel time for current trip patterns.