Appraisal in the transport sector has a history extending back around 60 years, in terms of application at scale, with antecedents going back to at least the French economist and engineer, Jules Dupuit, a century or so earlier. The magnitude of most countries' transport spending, both public and private, together with the pervasive influence of transport on life opportunities and scale of transport external benefits and costs, provides continuing impetus to the development of the art and science of transport appraisal. Appraisal is typically (not always) government driven. Accordingly, development and refinement of appraisal methodologies is commonly spurred by government expectations about the justification required to support allocation of scarce public funds. This is particularly so in jurisdictions where the national government controls most of the purse strings and distributes largesse to lower levels of government (often a reflection of vertical fiscal imbalance) and/or to other stakeholders (e.g. businesses). The US, UK, Sweden, the Netherlands and Australia, for example, all have long histories in this area, particularly associated with expectations around appraisals to support federal/national government own-project requirements and also around requirements required to support funding flows from the national/federal government for initiatives sponsored by lower levels of government or other stakeholders. In turn, governmental appraisal requirements are often supported by production of appraisal guidelines, which describe government expectations and ways of meeting those expectations. The UK Treasury Greenbook (HM Treasury 2018a) and associated transport webtag materials is a wellrespected example. The existence of guidelines, in turn, has helped to stimulate the extensive back-end research evidence base needed by quality appraisal methodologies and to support the practical front-end applications of those methodologies that give credence to the value of both the guidelines and of appraisal as a process.