When we plan for the future, we naturally extrapolate past trends. But there is emerging evidence that travel in the twenty-first century will be different from travel in the twentieth century.
This is clear from the findings of the UK National Travel Survey, which shows a steady increase in the average distance travelled (by all modes except air) from 4500 miles in the early 1970s to reach 7000 miles in the mid-90s, largely the consequence of private investment in cars and public investment in roads, which together allowed faster travel. Growth then stalled: there has been little change in twenty years, and per capita growth seems unlikely to resume. So while in the twentieth century, growth of travel demand was driven by growing incomes, in the twenty-first century demand growth will be driven by population growth, which in Britain is quite rapid – another 10m inhabitants by 2040.
The future pattern of demand will depend on where these additional people are housed: if on greenfield sites, then they will use cars and investment in roads will be needed. But if they are accommodated in existing urban areas where there is little scope for additional road capacity, then public transport investment will be required.
London is a successful city, increasing population density within existing boundaries. Rail investment by the public sector makes brownfield land accessible for construction by the private sector, exemplified by the development of Docklands which accommodates London’s economic and population growth. Rail provides speedy and reliable travel and can get professionals out of their cars for work trips, even the 100,000 well paid people who work at Canary Wharf, the new financial services district, where few cars are to be seen and where accordingly the interactions between people contribute to the urban vibe. Rail investment is the key to the growth of cities that succeed through agglomeration – the economic, cultural and social benefits arising from higher population densities.
Car use in London peaked in around 1990 when 50% of all trips were by car, driver and passenger. It has since fallen to 36% as the population has grown in the absence of additional road capacity, with an expectation of around 27% by mid-century on current trends and policies. In the twentieth century, increasing prosperity was associated with increasing car ownership and use. In the twenty-first century, however, increasing prosperity is associated with decreasing car use in successful cities.
This raises a key issue for smaller cities: do they attempt to become less car dependent, through the stick of parking controls and the carrot of public transport investment, hoping to benefit from agglomeration; or do they aim to accommodate the car, the traditional approach? We are in a period in which public funds for transport investment are more available than in the recent past. The question for smaller cities is how to make best use of this investment.
One other important finding from the National Travel Survey is that average travel time has hardly changed over forty years – close to an hour a day across the population. This tells us that the benefits of the many £ billions of public investment over this period have not been taken as travel time savings, as the transport economists suppose, time which is valued because of the opportunity for more productive work or desired leisure. Rather, people take the benefit of investments that allow faster travel to go further in search of more opportunities and choices, for example of homes and jobs.
The implication of this unchanging travel time is that road investment intended to reduce congestion fails to achieve that aim – because the extra traffic from longer trips restores congestion to what it was. Hence the maxim that you can’t build your way out of congestion, which from experience we know to be generally true. If we are to tackle traffic congestion, we will need to new tools provided by the digital technologies, another important reason why travel in this century will be different from in the past era. For more, read my new book: Travel Fast or Smart? A Manifesto for an Intelligent Transport Policy.
David Metz is an honorary professor at the Centre for Transport Studies, University College London, and a former Chief Scientist at the Department for Transport.