Roadway Determinants of Bicyclist Multi-pollutant Exposure Concentrations

Due to poorly quantified traffic-exposure relationships, transportation professionals are unable to easily estimate exposure differences among bicycle routes for network planning, design, and analysis. This paper estimates the effects of roadway characteristics on bicyclist multi-pollutant exposure concentrations, controlling for meteorology and background conditions. Concentrations of volatile organic compounds (VOC), carbon monoxide (CO), and fine particulate matter (PM2.5) are modeled using high-resolution on-road data. This paper also compares exposure differences on immediately parallel high-traffic/low-traffic facilities and is the first study to quantify VOC exposure differences by facility. Results indicate that average daily traffic (ADT) provides a parsimonious way to characterize the impact of roadway characteristics on bicyclists’ exposure. VOC and CO exposure increased by around 2% per 1,000 ADT, robust to several different regression model specifications. The results have important policy and design implications to reduce bicyclists’ exposure. Separation between bicyclists and motor vehicle traffic is a necessary but not sufficient condition to reduce exposure concentrations; off-street paths are not always low-pollution facilities. Direct comparisons of exposure concentrations on parallel routes shows that minor detours to nearby low-traffic facilities can dramatically reduce exposure to strongly traffic-related pollutants