There is a concerning paucity of Post-decision Project Evaluation (PdPE) of public private partnership (PPP) projects, given how significant this model of public infrastructure delivery has become. Drawing from previous academic and policy proposals, we explore the evidence of PdPE in the planning practice of UK PPP projects. Our findings suggest the planned practice for PdPE is under-developed and ambiguous. IMPACTAlthough the UK is no longer developing new PPP projects there are over 700 existing projects entering their mature operation stage. However, we know very little about how to evaluate whether these projects are still delivering expected outcomes. This paper provides policymakers and managers with an overview of how PdPE was represented at the planning stage of projects, as a basis for developing future PdPE frameworks.

PurposeThe authors explore the under-researched area of post-decision evaluation in PPPs (public–private partnerships), focusing upon how and whether Post-decision Project Evaluation (PdPE) is considered and provided for in United Kingdom (UK) public infrastructure projects.Design/methodology/approachThe authors’ research design sought insights from overviewing UK PPP planning and more focused exploration of PPP operational practice. The authors combine the extensive analysis of planning documents for operational UK PPP projects with interviews of different stakeholders in PPP projects in one city. Mobilising an open critical perspective, documents were analysed using ethnographic content analysis (ECA) and interviews were analysed using thematic analysis consistent therewith. The authors theorise the absence and ambiguities of PdPE drawing on the sociology of ignorance.FindingsThe authors find a long-standing absence and lack of PdPE in PPP projects throughout planning and operational practice, reflecting a dynamic, multi-faceted ignorance. Concerning planning practice, the authors’ documentary analysis evidences a trend in PdPE from its absence in the early years (which may indicate some natural or genuine ignorance) to different levels or forms of weak inclusion later. Regarding this inclusion, the authors find strategic ignorance played a substantive role, involving “deliberate engineering” by both public sector and private partners. Interview findings indicate lack of clarity over PdPE and its under-development in PPP practice, deficiencies again suggestive of natural and strategic ignorance.Originality/valueThe authors draw from the sociology of ignorance vis-à-vis accounting's absence and ambiguity in the context of PPP, contributing to an under-researched area.