Throughout Europe, increased traffic in town and city centres has resulted in chronic congestion, with the many adverse consequences that this entails in terms of delays and pollution. Air and noise pollution is getting worse year by year. Urban traffic is responsible for the bulk of emissions arising from road transport. The number of road traffic accidents in towns and cities is also growing each year. Local authorities cannot face all these issues on their own; there is a need for cooperation and coordination at European level. With the publication of this Green Paper, the European Commission opens the debate on its role in addressing the challenges presented by urban mobility.