Assessment of cyclists' exposure to ultrafine particles along alternative commuting routes in Edinburgh

An effective promotion of commuting by bicycle requires a set of complementary actions, with one of the key measures being the definition of bike-friendly routes, both in terms of road safety and exposure to air pollution. In this study, bike commuters' exposure to ultrafine particles (UFP) was assessed using mobile measurements and video recording along three alternative routes from central Edinburgh to the science and engineering campus of the University of Edinburgh. Results indicate significant differences in UFP exposure across the three alternative routes, with mean particle number counts (PNC) of 7,990, 9,824 and 19,310 particles/cm(3) respectively. With respect to the different types of bike infrastructure present along routes, the findings suggest that bicycle boxes (spaces at intersections that allow cyclists to position themselves ahead of vehicle traffic) are effective for reducing UFP exposure and that using shared bus-bike lanes should be avoided where possible. Heavy duty vehicles (i.e. buses and trucks) and construction sites were identified as the main sources of peaks in UFP exposure. All routes in the city of Edinburgh showed markedly lower PNC levels than those reported by studies conducted in other cities. The findings of this study can inform the implementation of bike-sharing schemes and the design of future cycling infrastructure, for example in the context of developing the low emission zone proposed for implementation across Edinburgh for 2020.