In recent decades, in most western countries, conventional transport planning has encountered growing social opposition from environmentalists and increasing scientific criticism on the grounds of its unsustainability. In some places, including the United Kingdom, the assumptions, beliefs and values (‘storylines’) about transport have shifted to some degree away from the car in favour of public and slow forms of transport. The article elaborates a concept of ‘ecosocialization’ to describe and explain the various reform pressures that have sought to reorient transport planning away from car‐dominated approaches. We use this concept in preference to the more familiar one of ‘ecological modernization’ in order to foreground the influence of embedded value systems and habits, as well as institutions and rules, on key pathways of social development. Whilst these reformist pressures and their consequences have been evident for decades, it is also apparent that in other contexts, after moments of subordination to alternative policy settings, conventional car‐dominated transport planning has reasserted its pre‐eminence. Our article explores the shifting discourses and practices of transport planning in three national policy settings, charting the contest between critiques of car‐dominated approaches and those ‘countermodernizing’ forces, especially road building institutions, that have resisted this ‘ecosocialization’.