Some policy analysts worry that if per capita wealth in China continues to escalate and approaches that of the United States, automobile ownership could quadruple. The likely consequences: extreme traffic congestion and even higher concentrations of air pollution and planet-warming carbon emissions. But researchers are all over the map as to how much massive increases in personal wealth in China will impact private car ownership levels and vehicle travel. Complicating their estimates are vast regional differences in economic growth rates; the emergence of vehicle ownership restrictions in some of China’s most densely populated cities; and common, yet unproven, assumptions that China’s car ownership growth will resemble that of the U.S., South Korea, and other countries during periods of rapid economic expansion.