凌晨3点，记者跟着他们在海河下隧道走了1万多步

Core Viewpoint - The article highlights the dedication and hard work of the maintenance crew responsible for ensuring the safe operation of high-speed trains during the Spring Festival travel rush, emphasizing their round-the-clock efforts to address potential issues in the railway system [2][11]. Group 1: Maintenance Operations - The maintenance team, consisting of personnel from the Tianjin Power Supply and Electrical Departments, conducts inspections during a designated window of 3 hours and 40 minutes, focusing on critical components such as the contact network and switch gaps [3][5]. - The precision required in maintenance tasks is underscored, with specific tolerances for switch gaps set at 1.5 mm ± 0.5 mm, indicating the high standards necessary to prevent safety hazards [5][7]. - The use of advanced technology, such as drones equipped with high-definition cameras and infrared thermal imaging, has significantly improved inspection efficiency, reducing the time required for a kilometer of track inspection from 1.5 hours to just 22 minutes [8][9]. Group 2: Working Conditions - The working environment in the tunnels is described as harsh, with cold temperatures and challenging terrain, which the maintenance workers have adapted to over time [6][11]. - The physical demands of the job are evident, as workers experience discomfort from the cold while performing high-intensity tasks, necessitating careful management of their clothing to prevent overheating and subsequent chills [7][10]. - The article emphasizes the emotional commitment of the maintenance workers, who view their role as a responsibility to ensure the safety of travelers during the busy Spring Festival period [11][12].