This paper considers the different approaches applied to determine the requirement for additional infrastructure construction for different transport modes in Britain. Transport infrastructure is usually built to meet three main goals. The first of these is to stimulate the economy, by increasing connectivity and enabling economic growth by reducing transport costs (both time-based and monetary). The second goal is to increase the efficiency of both the transport system and wider society, by reducing congestion and journey times, while the third is to reduce transport’s negative impact on the environment, by cutting noise, air pollution and carbon emissions.
Historically, as transport modes have developed the initial approach taken to infrastructure construction has been one of predict and provide. In Britain in the 18th and 19th centuries this was driven by the private sector, with successive ‘manias’ for canal and railway construction. This approach was though found wanting as it led to overprovision of infrastructure, with in some cases actual traffic never coming close to promoters’ expectations, and in others unnecessary duplication of routes as a result of competition between companies. Even if traffic did not always grow to the extent that promoters had hoped, the provision of both railways and canals led to a huge growth in overall travel volumes, although traffic on both modes then declined as successor modes gained in importance. In the 20th century a similar predict and provide policy was adopted for road transport, this time driven by the public sector. Infrastructure construction was particularly rapid in the decades following WW2 which saw a huge expansion in the motorway and trunk road network, with the aim of speeding travel by car. While this objective was undoubtedly met, at least initially, the release of latent demand meant that traffic growth vastly exceeded the expectations of the planners. This meant that the new roads did not provide a long term solution to congestion, and the additional traffic generated huge externalities in terms of noise and pollution. The realisation that construction could not eradicate congestion led to a paradigm shift, with a move away from large-scale road construction in the late 1990s. Attention was instead focused on relieving pinchpoints, and the use of pricing to constrain and redistribute demand was considered.
However, recent policy developments suggest that the lessons of the past may not have been learned by current policy makers. The Department for Transport’s recent Draft National Policy Statement for National Networks suggests that as national road pricing has been “ruled out” and demand constraint measures do not reduce pressure on the strategic road network, new capacity on this network may be needed “to meet demand”. This apparent return to a policy of predict and provide has potentially serious implications for our ability to meet environmental targets, as latent traffic release could easily undo the benefits achieved through improved vehicle fuel efficiency.
Construct or constrain? Intermodal inconsistencies in infrastructure interventions (pdf, 2.2 MB). The future of national infrastructure systems & economic prosperity conference, Cambridge, UK, March 27–28.