Traffic congestion has been a perennial theme on writing about urban life since at least the Roman period. David Rooney's expansive, creative and conceptually sophisticated monograph investigates responses to traffic congestion in twentieth-century London when the traffic problem acquired a new shape and increased salience due to the explosive growth of motor vehicles.

Rooney's approach to traffic is informed by researchers who have brought the study of networked technologies and infrastructure into critical conversation with scholarship on material culture. For Rooney, traffic is not simply ‘a case of speed, volume and flow’ (p. 129), but rather ‘a socio-technical network of actors, both human and non-human, situated in sociological and political contexts with histories’ (p. 15). His approach complements the work of urban historians like Simon Gunn and Susan Townsend, who have applied insights from critical theory and sociology to the subject of urban mobility in the twentieth century. Rooney's conceptual framework also draws on Steven Graham and Nigel Thrift's work on failed states of infrastructure. For Rooney, congestion is not only an example of mobility in a failed state, but an inevitable corollary of mobility. He unpicks the notion that traffic congestion is a deviation from a natural state of unimpeded traffic flow, arguing that the ‘traffic problem’ must itself be problematized. Rooney deconstructs and contextualizes the various discourses of traffic that circulated in twentieth-century London to show that debates about traffic congestion were proxies for contests between different ideological and professional groups over wider political and socio-economic issues. These debates encompassed the control of bodies, the regulation of capital, the management of markets and the ordering of urban space. Rooney argues that the pre-eminence of celebrated planners in much existing historiography has obscured the contributions of other disciplines. He shows how civil engineers, police officers, economists, scientists and private developers challenged the urban planning orthodoxy. His dramatis personae includes not only elites, but middle-ranking officials, working across the city, not only in central London. Operating on the margins of the planning profession, they nonetheless exerted a powerful influence on the way urban mobility was conceptualized and physically restructured in this period. This perspective encourages us to think more broadly about who practised planning in this period.

Rooney investigates the influence of policing ideas on the traffic problem through the work of Alker Tripp, Metropolitan Police traffic commissioner between 1932 and 1947. Tripp believed the traffic problem was an instance of urban disorder, stemming from the failure to properly control different groups of road users. His solution was to segregate pedestrians and motor vehicles in space and time through guard-railing, signal-controlled crossings and laws prohibiting jaywalking. Rooney shows how traffic police sought to categorize and control the bodies of people alongside motor vehicles. Rooney argues that Tripp's approach to traffic policing was part of a transnational ‘culture of categorisation and exclusion’, which informed racial segregation around the globe. While planners and politicians tended to view traffic congestion as the product of inadequate infrastructure, economists characterized traffic congestion as an instance of market failure. They contended that road pricing would furnish motorists with the information and incentives they needed to make more rational choices, which would harmonize the demand for road use with the supply of road space. Rooney's account of the dynamic political trajectory of road pricing nuances our understanding of party ideology. Promoted by neoliberal think-tanks in the 1970s, road pricing was ultimately eschewed by the Conservatives, but in the 1990s it was reimagined by Labour as a tool for combating the adverse environmental effects of road traffic.

If road pricing remained politically contentious, the idea that the existing road network could be managed more efficiently, obviating the need for expensive new construction projects, had persistent appeal. Rooney shows how a network of scientific professionals sought to use advanced technology to manipulate traffic flows and alleviate congestion on existing roads. In a 1960s experimental scheme in west London, a web of censors was used to capture data on vehicle movements, enabling computers to model traffic flows and co-ordinate traffic signals across a wide area. In the 1970s, the Metropolitan Police collaborated with the Greater London Council to expand the network of traffic cameras across the city as a tool for policing political demonstrations and maintaining public order. Here, Rooney illuminates the symbiotic relationship between the policing of bodies and traffic management. He also explores the role of private capital in steering responses to traffic congestion. Developers’ proposal for large schemes prompted complex negotiations between planners and property developers over traffic management. Rooney argues that the traffic problem created opportunities for profit-making. At St Giles Circus, property developers leveraged the traffic problem to obtain permission for Centre Point by providing land that the London County Council needed for a new roundabout. The Pimlico Precinct Project in Westminster sought to limit the deleterious environmental effects of traffic in the area, but this proved to be a boon for property speculators.

Rooney's argument that the way Londoners understood traffic congestion in the twentieth century was shaped by a multitude of ideologies, professional practices, technologies and private interests is compelling. This remains the case in twenty-first-century London where the tendency to privilege motorized traffic has been challenged, if not supplanted, by a philosophy that foregrounds walking, cycling and public transport. Rooney's book illuminates the intellectual antecedents of this ascendent approach and offers a framework for understanding the contemporary politics of traffic congestion. Conflicting definitions of the traffic problem animate debates over low traffic neighbourhoods, the Silvertown Tunnel, Uber, congestion charging and cycling infrastructure. These contests are underpinned by tensions between different groups of road users, between private capital and local residents, between new and old technologies and between different tiers of government. Rooney's book is thus exceptionally salient, and it can be highly recommended not only to urban historians and scholars of science and technology, but also to policy-makers, community activists and transport professionals.