The growth potential of the economy could be released by a reduction in transaction rather than production costs, which allowed agricultural and industrial goods to be exchanged more cheaply, so reducing market imperfections and encouraging areas to specialize in those goods to which they were best suited. Such a process of specialization could have a greater impact on total costs than changes in production technology, which could well emerge from an ability to concentrate on one commodity and to devise new methods of production and organization. Above all, transport costs could impose severe limits on the creation of an integrated, competitive market, preventing low-cost producers from supplying a wide area and allowing high-cost producers to survive. The crucial point for understanding the chronology of British economic growth is: when did transport costs fall sufficiently to make a difference to specialization and competition? Can a case be made for a reduction in transport costs before the construction of canals in the late eighteenth and early nineteenth centuries, by placing an emphasis on investment in rivers, harbours, and roads, technical improvements in ships and wagons, or changes in business practices which allowed a better utilization of the transport system? Or was a significant drop in transport costs delayed until the age of canals and railways, which allowed an escape from constraints on growth at the end of the eighteenth century or even in the first half of the nineteenth century?
Transport developments in the late seventeenth and early eighteenth centuries were, at first sight, less spectacular and heroic than the construction of flights of locks, the engineering feats of impressive tunnels, embankments, and viaducts, and the incursion of railway lines into densely settled towns and cities. But there is a danger that the achievements of men such as Isambard Kingdom Brunel have obscured the less spectacular developments of his precursors, who devised better road surfaces, altered the design of coaches, modified the rigging or hull design of sailing ships, or improved access to harbours and rivers. These