China has been the world's largest auto market for 4 years running. Last year, more than 19 million new cars were sold in the country. All those vehicles on the road come at a cost to the environment, contributing to a serious air pollution problem. Chinese manufacturers have been developing cars that create less of an exhaust burden, including electric models. High prices, however, have worked against their gaining popularity. To try to build some enthusiasm, the government has started a program of free test–drives of eco–cars and free license plates. The plates for conventional cars are allocated by auction. The program profiles new vehicles displayed at the Shanghai Motor Show and investigates whether they're making inroads in the marke