Abstract:
Recent studies of personal exposure to ultrafine particles (UFP) demonstrate the marked spatial and temporal variation in concentrations experienced by cyclists whilst commuting through the commuter microenvironment. This study aimed to investigate the influence of the urban form characteristics on determining the exposure of cyclists to ultrafine particles in Auckland, New Zealand, where concentrations are thought to be primarily associated with traffic pollution. Cyclist exposure was explored while taking into account the influence of direct encounters with vehicle emissions. UFP concentrations were measured by a cyclist along a 9 km route from the suburb of Mt. Albert to the city centre in Auckland, New Zealand. The characteristics of the urban form were determined and matched to UFP concentration using GPS coordinates and ArcMap. Dust-mapping was used to identify the spatial and temporal variation of the cyclist’s exposure along the route, and exposure visualisation using mobile phone imagery was used to identify the contribution of direct emission encounters on peak and overall concentrations. Results from this thesis highlight the complex interactions between the underlying processes determining the cyclist’s exposure. Peak concentrations often occurred when the urban form was conducive to reduced dispersion, and the cyclist was passing through traffic flows altered by signal-controlled intersections or uphill gradients. However, the cyclist’s exposure was not related to the characteristics of the urban form alone. High concentrations of UFP were primarily associated with direct encounters with the vehicle sources of emissions. In summary, the exposure of a cyclist to UFP can be reduced by introducing cycling infrastructure that separates the cyclist from direct emissions. This is particularly important around signal-controlled intersections and uphill stretches where emissions are likely to be highest, and for the Auckland setting in which cycling infrastructure is scarce.