Photo taken on Jan. 26, 2022 shows railway workers at the Gyaca bridge and tunnel work area in southwest China's Tibet Autonomous Region. (Xinhua/Liu Zhoupeng)

LHASA, Feb. 7 (Xinhua) -- "K249+502; K166+700..." In a dark tunnel on the Lhasa-Nyingchi railway, Rinchen Tsering wrote a raft of numbers on the back of his left hand under the faint light of his cap-lamp.

The 36-year-old from southwest China's Tibet Autonomous Region has been a railway worker for 15 years. The numbers are his "security codes," indicating the maintenance conditions on bridge and tunnel equipment.

The codes mark the locations of tunnel diseases. Rinchen Tsering said "K249" is the number of kilometers corresponding to the bridge and tunnel section, and "+ 502" is the specific location where tunnel diseases appear.

The back of his left hand looks much rougher than his right hand due to the long-term recording of codes. "It's convenient to write them on the hand because I can see it with my head down," he said.

The main line of the Lhasa-Nyingchi railway stretches for 435 km. With complex geological conditions, 75 percent of the line comprises bridges and tunnels.

The Gyaca bridge and tunnel area where Rinchen Tsering and his team work includes 33 bridges and 18 tunnels. It accounts for 46.9 percent of the total length of tunnels along the railway.

Rinchen Tsering leads a group of young people with an average age of less than 25, responsible for the maintenance and repair of equipment in the area within 137 km, including the investigation and treatment in the off-road environment.

They are called "tunnel guards."

The codes recorded to ensure the safe operation of the railway are not only the numbers on the back of Rinchen Tsering's hand but also show the boldness and meticulousness of every tunnel guard.

At the Lengda No.2 bridge above the Yarlung Zangbo River, Zhao Haoze, a Generation-Z tunnel guard in a bright yellow safety vest with his strap fastened, opened the cover plate at the entrance of the hanging fence under the bridge deck.

Zhao climbed down slowly from the safety ladder, loosened and buckled the strap latch each step down the ladder until he landed safely, and began to check the situation of anti-seismic piles, bearings, and supporting pad stones in the fence.

"They write down what they learn every day in a small notebook -- as their codes," Rinchen Tsering said proudly.

To avoid the moving train, the railway maintenance and repair work can only happen by using the travel interval of the train.

From 10 p.m. to 6 a.m. the following morning, tunnel guards have to endure a low temperature of more than 10 degrees Celsius below zero. In the dim light of the cap-lamp, they check and repair every joint and drainage cover plate of the railway and do not miss any hidden dangers that may affect driving safety.

In 2021, China Railway Qinghai-Tibet Group Co., Ltd. handled 11.8 million passenger trips, up 12.3 percent from the previous year. The annual delivery volume of goods was 37 million tonnes, with a year-on-year increase of 1.2 percent.

By the end of 2021, the Lhasa-Nyingchi railway had transported 621,000 passengers and more than 7,900 tonnes of goods since it opened to traffic in June last year.

These tunnel guards braved the cold winter wind to eliminate cracks, cavities, water seepage, and other diseases in bridges and tunnels to ensure the safe operation of Tibet's first electrified railway during this year's Spring Festival travel rush.