Psychophysiological effects of walking in forests and urban built environments with disparate road traffic noise exposure: A randomized controlled trial

People in urbanized societies commonly visit greenspaces to alleviate stress and promote restoration and well-being. However, access to greenspaces is often limited and road traffic noise remains a major environmental stressor in urban areas. While various studies have compared the benefits of exposure to greenspaces and urban built environments, the role of traffic noise in shaping these effects remains understudied. This randomized, controlled field study compared the psychophysiological benefits of exposure to forests and urban built environments with different levels of road traffic noise in 354 healthy adults during 30-min walks in Zürich, Switzerland. A range of physiological and psychological outcomes were measured. Linear mixed-effects models showed that walking in forests, in environments with lower road traffic noise and longer relative quiet time without road traffic noise was associated with increased feelings of restoration, subjective stress recovery, and perceived restorativeness, compared to walking in urban built environments with higher road traffic noise as well as such with less relative quiet time. These associations were not observed for salivary cortisol and for attention, though cortisol levels decreased in all conditions, likely due to walking itself. Findings from quantitative and qualitative data on soundscape-induced positive and negative affect showed discrepancies, indicating a need for developing and using affective measures that include low activation affect. Our results suggest that even when noise exposure is relatively low, it can still impede subjective restoration and subjective stress recovery. This highlights the need for noise mapping and mitigation strategies to reduce noise exposure, specifically in public greenspaces. The results further underscore the importance of noise-free periods, without road traffic noise. When planning, designing, and/or preserving urban environments to support the well-being of inhabitants, road traffic noise as an impediment to subjective restoration and subjective stress recovery should be addressed. • Restoration and subjective stress recovery were higher after walks in forest vs. urban sites. • Neither environment nor road traffic noise affected physiological stress and attention. • Road traffic noise hinders subjective restoration, highlighting its negative impact. • Noise-free periods are important, going beyond a reduction in the average noise levels.