Workers reinforce the guardrail along the Qinghai-Tibet Railway in southwest China's Tibet Autonomous Region April 20, 2006. The construction of the Qinghai-Tibet Railway, the world's highest, is in the last sprint. Its trial operation is scheduled on July 1. (Xinhua Photo)

An engineering vehicle maintains the Qinghai-Tibet Railway in snow in southwest China's Tibet Autonomous Region April 19, 2006. (Xinhua Photo)