Every year during the Spring Festival travel rush in China, train platforms bustle with passengers, few of whom notice the critical work happening beneath the train carriages. Hidden within the exposed wheels lies the critical cog to ensuring a safe journey.

In the wheel and axle workshop of the China Railway Taiyuan Group's Taiyuan Railway Vehicle Depot, 36-year-old Gao Bincheng sits on a low roller stool, meticulously measuring the axle journey of train wheels. He is committed to controlling the measurement precision to 0.001 millimeters — a minuscule error margin comparable to about one 80th of the diameter of a human hair, yet crucial for the safety of countless travelers.

Technician Gao is primarily responsible for measuring axle diameters and assembling bearing inner rings. He and his colleagues work tirelessly with wheels and axles, dismantling, repairing and reassembling them with a single goal in mind: to ensure the smooth operation of the trains.

Every day, Gao completes the measurement of 12 to 16 sets of wheels for regular-speed trains.

"I conduct precise measurements at 21 points on each wheel set using tools like an outside micrometer. During operation, I must maintain a stable posture, gripping the micrometer handle with my left hand and adjusting the knob with my right, while keeping a close eye on the numerical changes to ensure accuracy," Gao said.

The measurement results are directly used in the intelligent bearing selection system, providing precise data for subsequent bearing assembly and effectively preventing safety hazards.

A wheel set's life span is about 22 to 25 years, and the Spring Festival travel rush is its busiest time.

The 2026 Spring Festival travel season began on Feb 2, marking the start of a 40-day period known as the largest human migration in history. Returning home for the Chinese New Year is a cherished wish for everyone, and train travel is a vital choice for many.

Gao grew up surrounded by the clatter of train tracks. With generations of his family working in the railway industry, the dream of contributing to the railway had long taken root in his heart.

In 2013, after retiring from the military, Gao joined the wheel and axle workshop at the Taiyuan Railway Vehicle Depot.

"We've considered fully replacing manual measurements with automated machines, but under current conditions, it's not feasible," said Hao Yanlong, deputy director of the wheel and axle workshop. "While automated machines offer precision, they lack the experience and analytical ability of our workers. When encountering special wear points, machines cannot flexibly select new measurement points, which can bring inconvenience to subsequent bearing selection and affect operational efficiency."

In the Chinese railway system, the principle that "there are no small matters with wheels and axles; millimeters determine safety" is ingrained in every maintenance worker's heart.

Over the years, Gao has earned numerous accolades, including "advanced worker of the Taiyuan section" and "star of Taiyuan Railway Vehicle Depot". Despite having 12 years of experience, he continues to learn and refine his skills in his spare time.

To ensure the quality of passenger train maintenance, the Taiyuan depot implements a strict system of oversight. It requires workers to conduct self-inspections, followed by re-inspections by the foreman and quality inspection department, and finally, a final verification by the acceptance office. This rigorous process is particularly crucial for the hidden nature of wheel and axle maintenance, ensuring that every step is thoroughly checked to promptly identify and eliminate potential faults.

"There are no shortcuts in this line of work; it's about practicing and refining repeatedly," Gao said."A strong sense of responsibility is essential. I must be fully aware of the quality of my work.

After each day's work, I carefully review the day's operations; otherwise, I can't sleep peacefully."

He added, "Although we are not on the front line of passenger transportation, through our equipment inspection and assurance, we safeguard train operations and provide passengers with peace of mind for their journey."

Sun Hao contributed to this story.

Contact the writers at zhuxingxin@chinadaily.com.cn