On de-bunking 'fake news' in a post-truth era: why does the Planning Fallacy explanation for cost overruns fall short?

The Planning Fallacy has been heralded as the best theoretical perspective to explain ‘how projects work’, particularly within the transport area. However, we contend that the data and the resulting conclusions relied upon to support the Planning Fallacy have been based on methodological artifacts that do not stand up to close scrutiny. We suggest these flaws stem from ‘the compulsion to theorise’, which predisposes to explain every project behaviour by the Planning Fallacy. We then unpack the method and data used to support the ‘Planning Fallacy’. Therefore, we ‘open a new door’ for the development of a more robust theoretical explanation for ‘how projects work’.