Technicians inspect electric locomotive equipment at a service workshop at Houma North Locomotive Depot, China Railway Taiyuan Group, in Houma, Shanxi province, on Tuesday. Regular and precise maintenance of the equipment is the cornerstone of railway safety, underpinning the reliable operation of China's over 165,000-kilometer national rail network — the world's largest — which carries about 4.6 billion passengers and 5.2 billion metric tons of freight annually, serving as the backbone of the country's transportation system.