Scientists using equipment mounted on a Ford Falcon and a pedal bike are assessing the impact of Auckland's Southern Motorway on air quality in Otahuhu.
The National Institute for Water and Atmospheric Research (NIWA) and university researchers are also using sampling tubes on lampposts, and three air-quality monitoring stations.
They say National Environmental Standards for air quality and World Health Organisation guidelines might be breached along major roads.
Most of the instruments recorded their highest measurements in the morning rush hour, especially when there was little wind.
However, levels of particles were as high or higher on winter evenings when more people burned wood to heat their homes.
The full results will be available in 2012 and will help in planning new roads and urban design.
The study aims to find ways of reducing the number of people exposed to dangerous concentrations of air pollution close to motorways.