It has always been a controversial tool, generating accusations of unacceptable principle, improper application, inadequate evidence base and bias. One early application was to the appraisal of the proposed third London Airport where a critic labelled the project appraisal as “nonsense on stilts” and the method was defended against accusations of being “bastard science and/or insidious poison in the body politick” (Self 1970, Williams, 1973). Since that time, appraisal has found itself at the centre of public disputes about the road planning system, the treatment of environmental impacts, the socalled “roads generate traffic” issue and the relationship between transport and the economy. The…