Since the late 1990s, China's national road network has been significantly expanded through the creation of a network of national highways and expressways. In 2018, China's highways had reached a total length of , making it the longest highway system in the world. China has the world's largest market for automobiles, having surpassed the United States in both auto sales and production. A side-effect of the rapid growth of China's road network has been a significant rise in traffic accidents, though the number of fatalities in traffic accidents fell by 20% from 2007 to 2017. In urban areas, bicycles remain a common mode of transport, despite the increasing prevalence of automobiles – , there are approximately 470 million bicycles in China.