Restorative effects of highway roadside urban forests: A simulated approach

The health benefits of urban forests have been extensively explored with participants walking or viewing them, while this topic has rarely been investigated with participants driving. Additionally, research in this area has rarely explored the specific context of highway roadside urban forest. Simulated driving was employed to study the impact of six highway roadside landscapes on drivers' perceived restorativeness and physiological responses. These landscapes included one barren landscape (as a comparative baseline) and five urban forest types, namely shrub-sides, shrub-regular, shrub-random, tree-regular, and tree-random settings, each characterized by varying greenness and complexity. A sample of 38 participants took part in six 10-min simulated driving tasks in random order. Perceived restorative potential and driving fatigue restoration were measured using a questionnaire. Physiological indicators, including heart rate variability and skin conductance level, were measured using Wireless Photo Plethysmograph and Electrodermal Activity Sensors. The results indicated significant differences in drivers' perceived restorativeness and physiological reactions to the six types of landscapes. The tree-random condition was associated with a relatively more favorable perceived restorativeness and physiological state, while the barren condition resulted in the least desirable outcomes. Moreover, higher greenness was associated with better perceived restorativeness and physiological status for drivers. Furthermore, there were no significant differences in perceived restorativeness and physiological status between landscapes with high greenness and high complexity, and those with high greenness and moderate complexity. The study highlights the perceived restorative and physiological benefits of highway roadside urban forest landscape and provides valuable guidance for their design.