Railway worker Feng Weidong checks a light tower beside tracks in Kunming, Yunnan province.
A dedicated team of young maintenance workers is helping keep the lights shining on 671 kilometers of railway line in Yunnan province.
The 21 members of the team - average age just 24 - work at night as they check the thousands of bolts on light towers and bridges on two new lines.
Selected for the special duty in July from more than 1,500 repairmen at China Railway Corp's Kunming branch, they methodically check over 60,000 bolts over the course of three months before starting the process again.
Late each night, after trains stop running on the Shanghai-Kunming high-speed line and the Yunnan-Guangxi line, the team starts work, climbing light towers and bridges to check every bolt. They finish by breakfast time and rest up during the day.
It is nearly 11 pm when they push through the weeds along the lines to reach the 25-meter-high light towers to begin their climb.
"The first time I climbed a light tower, I was so scared because I felt it shaking and was worried it would collapse," team leader Dai Bing, 28, said.
Team members each carry 3 kilograms of safety ropes and maintenance equipment on their climbs. The higher they get, the thinner the tower becomes and the more violently it shakes.
"As time went by, we just gained more experience," Dai said. "The trick is to move with the tower as it shakes."
On each tower, the workers loosen and retighten every bolt, applying a special coating to prevent the bolts from slipping.
A light tower has over 1,200 bolts and a bridge many more, and there are 104 light towers and bridges along the two lines as they cross Yunnan.
"We can check two light towers a night and will spend nearly three months finishing all the light towers and bridges," Dai said. "Apart from the bolts, we should also check the lamps and tidy up the electric cables."
The work requires physical strength, mental agility and perfect teamwork to overcome the stresses and risks.
Team member Yin Chengkun, 23, unconsciously unhitched two of his three safety ropes when working one night because he had a bad cold. Luckily, a colleague yelled out to stop him from unhitching the last rope.
"If I'd untied the last rope, there's no doubt that I would have fallen," he said. "Even after doing the job hundreds of times, you would die if you made a small mistake."
Another team member, Zhao Xian, also had a narrow escape. "It was rainy and I just slipped and was actually hanging in the air," he said. "That scared me so much."
Not wanting their families to worry, most team members have not told their parents about the work they do. Han Weihu is one of them.
"One time when I'd just finished work in the morning, my mother called me, complaining that my phone wasn't available for the whole night," he said. "I just lied that I'd slept early and had switched off my phone."