Green Days in Geneva.

BMW debuts a 1-series three-door variant with a stop-start system and brake energy regeneration that will reduce fuel consumption and CO2 emissions. At the Geneva auto show next week, carmakers will demonstrate how they are making cars more fuel efficient. Automakers are being pressured by European Union legislators to curb CO2, the gas mainly blamed for global warming. And they need to show that they are developing more environmentally friendly powertrains.