There are three main sources of uncertainty in transport forecasts:

i The future path and values of the variables used in a model (eg GDP or oil price) may diverge from predicted values

i The specification and stability of statistical relationships used in the model may change over time

i A model may leave out of factors that do not currently affect consumer behaviour but may in future be important determinants of transport demand eg Eurotunnel predictions did not take into account the advent of low cost air flights between London and Paris

Remember: relationships based on past trends and patterns of consumer behaviour may not always be accurate for predicting behaviour in the future. Consumer tastes change and markets go through life cycle phases. Eg is air transport a growing or mature market?

• Transport Trends presents an overview and analysis of trends in transport and travel in Great Britain over the past twenty five years, and highlights some of the key issues.
• It is intended as a companion volume to Transport Statistics Great Britain, which contains reference tables containing more detailed figures and, in some cases, longer time trends.
• Transport Trends includes a wide range of indicators and statistical analysis to illustrate longer-term trends and to help put key policy targets and trends into a broader context. The report includes trends in relation to the Department's Public Service Agreement (PSA) targets and the government's sustainable development indicators which are most relevant to transport.
• Transport Trends 2008 is released on 12 February 2009 - you can download a PDF version from the introduction page or e-mail publicationgeneral.enq@dft.gsi.gov.uk for a free copy of the publication.

Transport trends current edition.