This paper seeks to abstract some general rules from the experiences with regulatory policy in the US transport sector and then to apply those rules to the challenges of environmental policy reform. The experience of the US transport sector is pertinent because it is an area in which regulations were imposed in one era—and then removed in another. What can be learned from this experience? What initially led to the imposition of political controls over this industrial sector, and what later led to their removal? What were the prerequisites for change, and what can regulatory reformers in other fields learn from this experience? In particular: When is change possible and how might it best be advanced?