A worker checks the vehicle barn of a bullet train in Shanghai Municipality, Dec. 19, 2012. Shanghai Railway Bureau conducted a comprehensive overhaul of all the bullet trains to ensure the demand of vehicles during the coming spring rush on Wednesday. (Xinhua/Chen Fei)

Technicians checks the chassis of a bullet train in Shanghai Municipality, Dec. 19, 2012. Shanghai Railway Bureau conducted a comprehensive overhaul of all the bullet trains to ensure the demand of vehicles during the coming spring rush on Wednesday. (Xinhua/Chen Fei)

Technicians checks the pantograph of a bullet train in Shanghai Municipality, Dec. 19, 2012. Shanghai Railway Bureau conducted a comprehensive overhaul of all the bullet trains to ensure the demand of vehicles during the coming spring rush on Wednesday. (Xinhua/Chen Fei)

A technician checks the braking system of a bullet train in Shanghai Municipality, Dec. 19, 2012. Shanghai Railway Bureau conducted a comprehensive overhaul of all the bullet trains to ensure the demand of vehicles during the coming spring rush on Wednesday. (Xinhua/Chen Fei)

A technician checks the power box of a bullet train in Shanghai Municipality, Dec. 19, 2012. Shanghai Railway Bureau conducted a comprehensive overhaul of all the bullet trains to ensure the demand of vehicles during the coming spring rush on Wednesday. (Xinhua/Chen Fei)