‘The nation’s principal means of allocating scarce road space among competing users during periods when too many people want to use that limited space at the same time’ (A. Downs 2004). ‘Combinations of public transport/cycling/traffic management measures (traffic calming, park and ride), are not enough to reduce traffic in city centres; restraint measures, such as traffic calming, parking controls or road pricing are needed as well. To achieve public/political acceptability for such policies, improved public transport, providing alternative means of travel, needs to be in place before the restraints are introduced. The danger is that once the situation improves, the cars will immediately return.

A reduction in congestion will have the potential to induce extra trips and traffic, which would not otherwise have occurred; all assessments of measures to reduce congestion should take account of the potential for induced traffic’ (House of Commons, Res. Paper 98/16). This term can apply to an excessive demand for any facility.