Bullet trains fuel real-estate booms, improve quality of life, reduce air pollution and traffic congestion, and provide a “safety valve” for crowded cities, especially in the developing world, according to a study by Chinese and U.S. economists. The study was based on China’s rapidly expanding high-speed rail network, but the researchers said the benefits experienced there would be similar for California’s proposed high-speed rail system. Bullet train systems connecting China’s largest cities to nearby smaller cities have made these “second tier” cities more attractive for workers and alleviated traffic congestion and pollution in megacities, according to the study, carried out by economists at Tsinghua University and the University of California, Los Angeles. The study found that the trains created a new category of exurbs within 60 to 470 miles of urban centers such as Beijing, Shanghai, and Guangzhou, helping keep people from moving to already crowded megacities. The study was published in the online version of the Proceedings of the National Academy of Sciences.