Potential pollution exposure reductions from small-distance bicycle lane separations

- Three cyclists collected air pollution data simultaneously during five afternoons, at separate distances from the roadway.
- The cyclists at 7 m and 19 m away from the road had substantially reduced exposure to several key traffic pollutants, compared to the on-road cyclist.
- Results are useful for informing city planning by promoting the development and use of segregated walk and cycleways.

Many studies have compared the exposure of cyclists to those taking other modes of transport and compared exposure differences between backstreet routes and main roads. In this study, we employ the use of three bicycles travelling in unison to sample concentrations of ultrafine particles (UFPs), carbon monoxide (CO) and fine particulate matter (PM1.0) at three different distances from the traffic flow, in a central city park area of Christchurch, New Zealand. Similar research has been done using stationary equipment, but this may not accurately represent exposure differences while moving with a stream of vehicles. Three cyclists were equipped with a set of identical instruments and rode continuously along a road, the road׳s sidewalk (7 m away) and an off-road path (19 m away), for a total of 6 h and 45 min, over 5 afternoon sampling runs during fall. Data were analysed in the form of linear mixed-effects models, with cyclist position (distance from edge of nearest traffic lane), wind speed, and temperature, having statistically significant effects on mean exposures (p<0.05). Mean exposure to UFPs and CO were approximately 20-30% (p<0.01) lower at the sidewalk and 40-50% lower at the path, than at the road (p<0.01). These results highlight the potential exposure benefits of segregating cycleways, which helps inform city planning. Separating cycle lanes on key routes could help reduce cyclists׳ cumulative intake of pollutants, especially on heavily-trafficked roads.