For nine years the city of Bermen, Germany has been encouraging its 550,000 inhabitants to abandon car ownership by supplementing an ulramodern public-transport system with a car-sharing scheme that allows citizens to rent a vehicle quickly at relatively low cost. Cities elsewhere in Germany and Europe are considering similar experiments. A European Union study showed that, if applied on a continental scale, such programs could reduce car, mileage by as much as 32 billion kilometers a year, which in turn would curtail carbon-monoxide emissions-believed to contribute to global warming-by as much as 5 million tons a year.