After starting his career during the era of steam locomotives, Sun Mingjin looks forward to touring country by bullet train

Train attendant Sun Mingjin is working through his 39th Spring Festival travel rush, which began on Jan 21 and will not officially end until March 1.

Known in China as chunyun, the period in which people traditionally return to their hometowns to celebrate the Lunar New Year, the travel rush has become known as the world's largest annual human migration.

During his career at China Railway Shenyang Group, Sun has witnessed China's railway development from steam locomotives to diesel and electric trains, and now bullet trains.

Sun, 59, has collected 16 different types of keys to train carriage doors, which he has kept as souvenirs of a rapidly changing era.

"I got the first key from my father who was also a train attendant," Sun said. "On my first day of work after graduating from senior high school in 1980, he handed me the key and asked me to take my job seriously.

"At that time, train carriages were made in different countries such as Germany, Japan and the Soviet Union. The locks were not designed according to a unified standard. Therefore, I needed at least five different keys during my duty on the steam locomotive trains."

Passengers could hear the sound of keys jingling when a train attendant passed by.

"For decades, trains were the top transport choice of travelers, especially before 2000 when there were hardly any other choices for long journeys," he said, recalling how crowded the carriages were during peak travel seasons. "Passengers were everywhere - on the aisles, under the seats, and even in the toilets.

"At that time, it took more than 24 hours to travel from Jilin city (in Jilin province) to Tianjin, which is about 1,000 kilometers away. Numerous times, I had to stand at the carriage door the whole night because there was no way of going back to my room through the 20-meter-long aisle."

Moreover, the extremely cold weather in northeastern China was a huge challenge for train staff.

"Cold winds came through the gaps of the train doors and the doors could easily become frozen," Sun said. "The train attendants needed to be strong enough to open the door when the train arrived at the station."

The situation improved after 1997, when most of China's steam locomotives were replaced by diesel models and air conditioners were installed in carriages.

"On a diesel train, one key could open all the doors due to a unified design standard," he said. "Hence, the previous heavy set of keys became part of my permanent collection.

"Furthermore, the speed of the trains increased to 140 kilometers per hour, which seemed unimaginable in the past. Thanks to the excellent sealing of the doors and air conditioning system, passengers could enjoy a warm trip even on the coldest days."

High-speed trains came into operation in 2007, opening a new chapter in the country's railway development.

"Even though I didn't get a chance to work on the high-speed trains, I've found that the crowd on ordinary trains during chunyun has declined greatly," he said. "More passengers prefer the faster way. The time between Jilin city and Dalian in Liaoning province - the route that I worked on - has been cut from 12 to four hours."

Sun continues working on the ordinary trains that provide convenience to passengers in regions where there are no high-speed trains.

"The trains have been upgraded to electric locomotives that run at 160 km/h, and it's quiet and more environmentally friendly," he said. "The keys have also become smaller and more exquisite.

"I've also applied for a key to the doors of high-speed trains. I will retire next year, but I hope I can keep all the types of keys."

He plans to travel around the country with his wife by train after retirement. Although he has spent most of his time on trains, he said he has seldom enjoyed relaxed train trips in the past few decades.

"I want to experience the new Fuxing bullet trains, which have not been seen in the Northeast," he said. "I believe it will be an unforgettable trip."