Measuring urban nature for pedestrian health: Systematic review and expert survey.

• 42 urban nature measures were used in 115 pedestrian health studies reviewed. • Reviewed studies predominantly used objective and aerial-level measures. • Perceptual, eye-level, and quality measures of urban nature were underutilized. • Area/proportion and proximity were the most common disaggregate measurement types. • Normalized Difference Vegetation Index was the most popular composite variable. Walking and access to nature are two of the most effective health promotion and disease prevention strategies. There has been a growing interest in the dynamic pathways among access to nature, walking, and health. Effective measurement of these variables is the prerequisite to advancing our understanding of such pathways. However, contrasting to the rigorous methods available for walking and health measures, methods to quantify nature have been limited. This study uses a systematic literature review to synthesize urban nature measures (UNMs) used in published studies linking urban nature with pedestrian health outcomes (e.g. walking, physical activity, physical health, mental health). A survey of experts (n = 30) was used to identify additional and emerging methods. The literature search identified 115 articles and 48 UNMs most of which (40 or 83%) were objective measures. Results showed no consensus on the optimal UNMs for pedestrian health research, but certain measures such as NDVI, proximity to green spaces, and area/proportion of green spaces, were popularly used in previous studies. Experts suggested emerging methods including LiDAR, GPS, high-resolution imagery, virtual/augmented reality, and context-sensitive ecological momentary assessment. Major gaps in current UNMs included the shortage of eye-level and quality-related measures. While experts acknowledge the promise of emerging technologies, they shared concerns related to privacy, digital divide, confidentiality, and bias. This study offers insights into the UNMs available to quantify nature for pedestrian health research, which can serve to facilitate future research, community actions, and policy changes aimed at promoting walking and nature access for healthier urban communities. [ABSTRACT FROM AUTHOR]