The historic high cost of personal vehicles led to the growth of demand for new shared modes of travel at much lower cost, in the form of mass-market public transport: trains in the nineteenth century, buses in the first half and air travel in the second half of the twentieth century. The heyday of public transport was reached in the middle of the last century. Subsequently, there was a very substantial shift to personal means of transport as the auto makers drove down costs through efficient assembly line technology, to the point where the car is now the main mode of travel in developed economies.

Yet public transport is far from being down and out. These traditional shared modes of travel are far more efficient at moving people in their use of road and rail infrastructure. The capacity of the road network constrains car use. Rail in all its forms has undergone a major revival in Britain and elsewhere, largely because it offers fast and reliable journeys compared with cars and buses on congested roads. In contrast, the situation of buses is far more variable and depends on local circumstances. Long-term decline in passenger numbers is common. Yet in some cities passenger numbers are growing, aided by policies that prioritize buses over cars.

The main question to be considered here is the likely impact on public transport modes of the new digital technologies that I discussed in the previous chapters. I will also review technological possibilities for extending the realm of public transport, above and below congested surface networks.

Digital railway

Digital technologies are having a profound effect on the railways, both in how we interact as consumers and the way in which trains are operated and managed. The convenience of making arrangements through well-designed websites has contributed to the growth of longer-distance rail travel, eliminating the need for intermediation by travel agents. The ability to flex fares and offer choices to passengers helps contain costs by matching demand with supply to gain revenue from seats that might otherwise remain empty, although often prompting criticism of an over-complex fare structure.