"I think the bullet train system is not stable and may break down in extreme weather conditions, " said Professor Zhao Jian, a transportation expert with Beijing Jiaotong University.

CNN: STORY HIGHLIGHTS

"In less than a decade, we constructed more high-speed rail lines than what it took Japan and Europe 40 years to build, " said Zhao Jian, an economics professor at Beijing Jiaotong University and one of the country's leading experts on rail transportation.

CNN: China's high-speed trains attract frustrated fliers