Evaluation of traffic control measures in Oslo region and its effect on current air quality policies in Norway

Urban air pollution is a challenge in several European cities. For most Norwegian cities, the major challenge is the reduction of the NO2 annual mean concentration in order to comply with the limit value in the European Directive 2008/50/EC, but also too many high NO2 hourly values occur during strong inversions in cold winter periods. In Oslo, the main contributor to NO2 concentration levels is diesel exhaust and hence the proposed measures in this study are targeting road traffic. An extensive array of individual and grouped measures were constructed and we studied the change in traffic and NO2 concentrations by performing consecutive modelling studies which included traffic, emissions, and dispersion models. These measures were intended for permanent and temporary action. They included increases of the tolls that give access to the inner parts of the city, the establishment of low emission zones (LEZs), allowing for temporary free public transport, odd-even driving, defining priority lanes for low emission vehicles, and imposing higher parking fees. We concluded that the most efficient measures were the creation of LEZs and the increase of parking fees. We also explain how the findings from this work have helped to implement Norwegian air quality control policies.