HARBIN, June 6 (Xinhua) -- It is a train that operates only once a year.

It takes students from north China's Greater Hinggan Mountains to a town 130 km away. There, they face perhaps the greatest challenge of their lives so far -- gaokao.

Gaokao, the national college entrance examination, takes place on June 7 and 8. About 9.75 million students have registered this year.

Lu Guiyi, a student in Dayangshu Township No. 2 Middle School, boarded the train on Tuesday with her classmates.

"The trip may be the last time we are all together," said Lu, a class monitor.

Lu has watched the "gaokao train" depart on its two-and-half-hour journey many times as generations of her schoolmates left for the examination, fates in the balance.

Dayangshu in north China's Inner Mongolia Autonomous Region is located at the southern foot of the Greater Hinggan Mountains. With no exam venue there, students like Lu have to travel across the mountains to Alihe township for the exam.

Every year, the "gaokao train" departs on June 5, with one-way ticket costing 12.5 yuan (2 U.S. dollars).

Before the chartered train service began in 2003, students had to get up at 4 a.m. to catch a train to Jiagedaqi before taking a bus to Alihe, six hours of travail.

Meng Li was one of the first batch of students who had enjoyed the service in 2003. She was thrilled to learn the opening of the "gaokao train" as she was worried that the bumpy journey would inevitably affect her performance.

"It was the first time many of us had taken a train. Some of my classmates had never left town before," said Meng, now a teacher in Dayangshu.

Since it began, the train has carried more than 30,000 students to their date with destiny. Of them more than 6,000 found places at university.

Given rising living standards and improved roads, many parents now drive their children to the exam.

The number of passengers, including students and parents, has declined from 1,300 at its peak to 500 this year, said Chen Ruqing, trainmaster of the Jiagedaqi section.

This year, the rickety old green train has been replaced with a newer one with air conditioning, and photographer on board will preserve the memories of what is a very special day in the lives of those aboard.

"Although we lose money by operating the train, we will keep running as long as it is needed," Chen said.