The Stockholm Congestion Charging Trial (SCCT) was implemented with the goal to satisfy a number of transport policy objectives related to reduced car travel in the central area of Stockholm. This occurred in a stormy political and legislative environment, and the definition of congestion that the charges were intended to alleviate was never clearly stated. The traffic impact evaluation efforts were based on survey results for chosen links without any scientific review of the dynamic character of congestion or the statistic characteristics of selected indicators of performance. Congestion can be defined as traffic conditions caused by a downstream bottleneck, or travel time increase compared to low traffic conditions . The selection of congestion performance indicators and data collection techniques must be carefully coordinated with the definition adopted to capture the true nature of congestion. The paper presents estimations of selected congestion performance indicators based on SCCT "before" and "after" survey data and own mobile data sources. The analysis considers estimations for both definition of congestion, for different data collection methods and among selected congestion performance measures available in the literature. The Statistical properties for these indicators are calculated as a basis for evaluation of suitable indicators for different purposes. Finally, the paper discusses the indicators from the point of view of applicability to on-line information sources, and usability for socio-economic analysis.
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