Official production of the new Dodge Dart is being launched in northern Illinois this week. The model is being assembled at the Chrysler plant in Belvidere. Local union officials tell Bloomberg Businessweek the first Darts intended for shipment will start rolling off the assembly line Thursday. Industry observers say this is the biggest test of the partnership between Chrysler and Fiat, which took control of the U-S automaker during its 2009 bankruptcy. 18-hundred jobs are being added in Belvidere to accommodate production of the new model. The Dart is the first Chrysler car based on Fiat design features.