This paper explores the mental-models of Swedish planners in order to understand the extent to which they support the ideals of sustainable transport. Focussing on three critical challenges: forecast-led versus vision-led planning; tackling congestion; and, public acceptability; the findings, drawn from in-depth interviews, demonstrate mostly advanced thinking. However, implementation can be at odds with these mental models, highlighting important lessons for other cities. There is a disconnect between the objectives of reducing car use and the continuation of investments in increasing road capacity, and a difficulty in transitioning from forecast-led planning to back-casting. Political controversies and public acceptability for measures to decrease car use are an added challenge.