After taking trains on three round trips from Harbin, Heilongjiang province, to Tianjin over the National Day holiday, Deng Zhike finally earned a rest.

"It takes only six hours for the 1,242-kilometer trip by a bullet train," the 45-year-old engineer for China Railway Harbin Group said. "When I started the job in the 1990s, I never expected that it would be so fast."

Over the past 25 years, he has covered 1.52 million kilometers, roughly 37 times the circumference of the Earth at the equator, without an accident.

Deng - who is licensed to operate steam, diesel and electric locomotives and now bullet trains - is proud of the rapid development of the country's railway system.

Living near a railway in his childhood, he always liked trains.

"Every time a train passed through, I would run out to look at it," he said. "I dreamed that one day I could sit in the cabin and pull the steam whistle."

After graduating from junior middle school, he chose a railroad school in his hometown of Suihua, Heilongjiang province.

Three years later, he began working as a fireman, adding coal to the firebox of a steam locomotive.

However, the gap between his dream and reality was a disappointment.

"You can't imagine how hard it was to work in a steam locomotive," he said. "At that time, I had to add about 10 tons of coal to the firebox during a 14-hour shift."

A steam locomotive typically requires three people - two engineers and a fireman - and it took more than seven hours from Harbin to Changchun, Jilin province, about 240 kilometers away.

"Handling the coal at work, I was all covered in black," he recalled.

Two years later, he obtained a license to operate a steam engine. In 1995, after driving a steam locomotive for several months, he stepped up to diesel at a time when most of the steam locomotives in China were upgraded.

"Only two people are needed for a diesel locomotive - an engineer and a conductor," said Deng. "The speed increased to 120 kilometers per hour, cutting time between Harbin and Changchun from seven hours to three."

"The operating environment was largely improved with no smoke and ashes in the cabin, but still a loud engine noise," he said.

He stayed with the diesel locomotive for 18 years and got his license for electric locomotives in early 2013.

"The electric locomotive runs at 160 km/h and it's quiet and more environmentally friendly," said Deng. "More amenities have been put in the cabin, such as a refrigerator, microwave oven and air conditioner."

At about the same time, the Harbin-Dalian High-Speed Railway, the world's first high-speed railway in a frigid zone, began operation.

"When I learned that only one driver was needed to operate the train and the high-speed link had reduced travel time between Harbin and Changchun to one hour, I wanted to have a try," he said.

However, it was not so easy for a 42-year-old to get a license to drive bullet trains.

"There was so much theoretical knowledge to learn, which was an enormous challenge to my poor memory," said Deng. "And most of the knowledge is different from what I knew about the trains I had driven, such as the structure."

"Thanks to my family members' support, I could focus on my new goal," he said. "I finished studying theory and took psychological and etiquette training courses before I got the license for the bullet train."

Finally, at the end of 2015, he realized his dream to operate bullet trains.

"The trains are not only faster but also equipped with more advanced devices," said Deng. "For example, Wi-Fi service is available on trains, and facial recognition technology is used for passengers entering the station."

"I am proud to have witnessed the great changes over the past decades," he said. "I hope I can stick to my post and participate more in the future."