Ambient environmental exposures while cycling on a vegetated trail versus the road

Abstract

Cycling can improve health, yet cyclists in cities may be exposed to hazardous conditions and have limited exposure to nature and its benefits. The purpose of this study was to measure and compare environmental exposures of urban cyclists on a vegetated, gravel trail route separated from cars and a fully paved route on local roads. In September 2021 in Austin, Texas, US, we cycled on the trail and road routes from 7:30–8:30 and 17:30–18:30 on one weekday and weekend day. While cycling, we wore sensors that measured fine particulate matter (PM2.5), total volatile organic compounds (VOCs), sounds, air temperature, relative humidity, light intensity, and geographic location. We used a neural network to distinguish anthropogenic and natural sounds. After time-matching all sensor data, we specified linear mixed effects models to test the association between route type and each environmental exposure, adjusting for afternoons and weekdays. We also used inverse distance weighting in GIS to map spatially continuous estimates of environmental exposures for each cycling trip. Compared to the road route, the trail was associated with higher levels of PM2.5, total VOCs, natural sounds, and relative humidity, and lower levels of anthropogenic sounds, temperature, and light intensity (p < 0.05). Mapping illustrated differences in environmental exposures within and between routes by time of day and day of week. Assessing exposures on existing and planned cycling routes may help inform the design of health interventions (e.g., tree planting along routes) in the face of increasing climate-related hazards.