Stuttgart’s geographical location in a valley basin, along with its mild climate, low winds and surrounding industries have made it susceptible to poor air quality. Continuous air monitoring indicates high levels of traffic-related emissions (especially particulates and nitrogen oxides), with European limit values exceeded on some of Stuttgart’s busiest roads.
Under the CARAVEL project, various measures were designed, implemented and assessed in an effort to reduce air pollution and fulfil the requirements of the European Clean Air Directive. This included the Clean Air Programme and Action Plan, which were launched in December 2005. Access restrictions are the most effective means to permanently reduce the number of vehicles entering and passing through the city centre.