Darker nights, happier lives? The impact of urban green space night-time accessibility on residents' subjective happiness: A case study of the main urban area of Hangzhou

The impact of night-time service functions in urban green spaces on residents' happiness has long been overlooked. This study explores the concept of ‘darkness well-being’ to examine the relationship between the night-time accessibility of urban green spaces and residents' subjective happiness, thereby providing a scientific basis for night-time-friendly urban planning. Using Hangzhou's main urban area as a case study, a night-time accessibility index for urban green spaces is constructed by integrating night sky quality and accessibility models based on multi-source data. A spatial map of night-time urban happiness is generated using natural language processing techniques. A multi-scale (150/300/450/600/750 m) spatial radius analysis framework is constructed, incorporating spatial autocorrelation analysis, key factor evaluation and multi-scale spatial modelling. Three time-threshold scenarios (5/15/30 min) are considered for both walking and cycling modes. Systematic analysis reveals that the spatial distribution of the residents' happiness index and night-time accessibility of urban green spaces is highly heterogeneous across the study area under varying temporal and spatial conditions. The relationship between the night-time accessibility of urban green spaces and residents' subjective happiness is subject to scale effects. Night-time accessibility is a key determinant of happiness, exhibiting a significant positive spatial correlation at the 30-min walking and 5-min cycling thresholds.