Traffic-generated pollution contains particles and gases (eg, oxides of nitrogen) that are known to have health effects.1 Concentrations of pollutants emitted by motor vehicles are highest within 150 m of roadways and remain raised up to 300 m from roadways, but fall off markedly beyond that range.2 3 Exposure to the mixture of traffic-generated pollutants may be more relevant to human health than exposure to any single ambient air pollutant, making epidemiological investigations of traffic effects a key component of research into the public health impact of air pollution. However, assessment of exposure to traffic-related air pollution can be problematic. Exposure to traffic can be estimated with complex dispersion models of pollutants from local freeway and non-freeway sources, but the data inputs required for such modelling are not always available. A frequently used simpler approach has been to estimate residential distance to roadways.

A number …