This report presents the results of the analyses of the road traffic measurements1 made by the City of Stockholm Traffic Office in order to evaluate the effect that the Stockholm Trial has had on traffic. The purpose of the report is to assess whether the objectives of the Stockholm Trial have been achieved and to ascertain whether the effects that have been measured can be attributed to the introduction of congestion charging. The road traffic-related objectives of the trial are to reduce the number of vehicles passing into and out of the congestion-charge zone during the morning and afternoon/evening peak periods by 10-15% and to improve system throughput (i.e. the fluidity of traffic) on the busiest streets and roads in Stockholm. This report is also one of several that provide a basis for assessing the degree to which the other two objectives of the trial (namely, reduced emissions and an improvement in the environment in the city) have been achieved. Another purpose of the investigation is to study how traffic on various sections of the road network has been affected at different times of the day, in order to determine whether there are any differences in the extent to which the objectives have been achieved. Finally, a more general purpose is to acquire more detailed knowledge about road traffic in Stockholm and the ways in which the introduction of a measure such as congestion charging affects driving habits.