Garbage in, gospel out? - Air quality assessment in the UK planning system

In the United Kingdom, the planning process requires applicants to submitan air quality impact assessment wherever an impact on national limit com-pliance is likely, and this factors into the resultant decision. We identify flawsin the current methodological frameworks and policies associated with thisprocess that in the worst cases could lead to poor decision making. We giveexamples of how inaccurate data is certified as good through unsuitable pre-processing, how these errors are then amplified by poor modeling practice,and how the final data is judged against metrics that are evidence impairedto arrive at potentially unsound decisions. We then discuss the implicationsand propose a way forward.