This book provides a political history of urban traffic congestion in the twentieth century, and explores how and why experts from a range of professional disciplines have attempted to solve what they have called 'the traffic problem'. It draws on case studies of historical traffic projects in London to trace the relationship among technologies, infrastructures, politics, and power on the capital's congested streets. From the visions of urban planners to the concrete realities of engineers, and from the demands of traffic cops and economists to the new world of electronic surveillance, the book examines the political tensions embedded in the streets of our world cities. It also reveals the hand of capital in our traffic landscape. This book challenges conventional wisdom on urban traffic congestion, deploying a broad array of historical and material sources to tell a powerful account of how our cities work and why traffic remains such a problem. It is a welcome addition to literature on histories and geographies of urban mobility and will appeal to students and researchers in the fields of urban history, transport studies, historical geography, planning history, and the history of technology.