Infrastructure management has traditionally been based on a logic of predict and provide in which rising demand was met with an increase in infrastructure capacity. However recent changes in political, economic, and environmental priorities mean that projects such as new roads, which simply expand supply, have become more controversial, and that reducing demand is now a key challenge. This article is about the different ways in which infrastructure managers have tried to achieve reductions in demand, as well as the range of plans that blend various proportions of technological and institutional innovation For the sociology of science, the controversies over these urban environment plans are interesting not just because they are scientific controversies but because they are controversies over the relationships between science, expertise, technology and society. As a result, the authors argue that sociologists of science have a contribution to make as experts in their own right. This article argues that the sociology of scientific knowledge (SSK) needs to move beyond symmetry and neutrality and outlines some of the ways in which SSK can make a difference by repositioning itself at the center of contemporary policy debates.