Urban and regional policies are key to achieving carbon neutrality as the majority of the global population is now living in urban built environments. However, progressive national agendas have been emerging, but institutional barriers often persist in constraining policymakers from guiding sustainable land use-transport coordination. This chapter argues that the research tradition of historical institutionalism (HI) offers insights into understanding and overcoming these barriers, helping explain current policies by identifying path dependence and power contestation rooted in contingent decisions over time. It considers the case of Tokyo to show that past policy choices shape recent contestations between carbon-emissive automobiles and low-carbon electrified railways. In Tokyo, the contingent absence of private automobiles owing to industrial policies until the mid-twentieth century delayed the progress of sustainable transport planning. This allowed pro-development coalitions to accelerate highway construction in the late century and led to Tokyo’s puzzling metropolitan structure today: a transit-served inner city and automobile-reliant outer suburbs. These sequential events suggest that reformers should deliberate path dependence on layered development agendas set by powerful actors to advance sustainable transport and land use planning and overcome institutional barriers toward achieving carbon neutrality.