The Geography of Green Deficits: Creating a 3-30-300 Measure for all UPRNs in Great Britain

The 3-30-300 rule has emerged as an influential benchmark for equitable urban green space provision, specifying that every home should have visibility of 3 trees, 30% neighbourhood tree canopy cover, and access to public green space within 300 metres. Despite growing international application, there is no GB-wide assessment of how households meet the rule. This paper presents the first nationally consistent operationalisation of the framework at the highest possible spatial resolution, calculating indicators for approximately 40 million Unique Property Reference Numbers (UPRNs) using high-resolution tree mapping, open green space data, and network-based pedestrian routing. We generate the 3-30-300 indicators as contin- uous measures, enabling assessment under canonical and alternative threshold specifications. Results reveal a substantial national green deficit: only 0.7% of urban UPRNs satisfy all three thresholds, with the 30% canopy criterion the binding constraint. The three components decouple both spatially and socio-economically. Tree visibility and canopy cover concen- trate in affluent southern suburbs and exhibit steep positive deprivation gradients, whereas proximity to formal green space marginally favours the most deprived urban neighbourhoods, reflecting inherited civic park provision in dense industrial- era cities. Composite compliance is nine times higher in the least deprived decile than the most deprived, a pattern robust to threshold relaxation. We argue the framework is best understood as three distinct policy levers rather than a single standard, and that place-sensitive, component-specific targeting is required to avoid widening the inequalities the rule seeks to ad- dress.