Stockholm Congestion Pricing Trial

Summary

Stockholm's congestion pricing trial is the gold standard for evaluating road pricing. The 7-month trial produced an immediate 22% reduction in traffic volumes and a 14% drop in emissions within the cordon. Uniquely, the scheme went to a public referendum after the trial — and voters who had experienced the trial approved it by a comfortable majority, despite initial opposition. Traffic volumes in the first year of permanent operation were virtually identical to the trial year, suggesting no rebound effect. The trial is notable for demonstrating both behavioral effects and political feasibility.

Research question

"Does congestion pricing reduce vehicle entries to the inner city and improve traffic flow?"

Methodology

Result

Positive

Traffic volumes fell 22% during trial; CO2 emissions near cordon fell 14%; public transit ridership +6%; effects persisted fully after permanent implementation

Evidence strength

Limited

Observational or pre-post design; correlation not necessarily causal.

Replication status

Replicated