As it enters the fourth quarter, Shanghai Suburban Railway Airport Link Line is in full swing, with tasks in the trial operation advancing steadily. Currently, the continuous over 20 days of train operation based on weekday schedule has been successfully completed, and full efforts are being made to achieve the opening goal. Behind this bustling scene are the wisdom and sweat of CASCO engineers who have worked tirelessly day and night, as well as their unspoken thoughts.

Shanghai Suburban Railway Airport Link Line is the first line in China to adopt the CTCS-2+ATO signaling system while also supporting the bus-like operation. CASCO is responsible for the integration, production, supply, installation, testing, and delivery of the signaling system. Compared to previous national railway projects, this project innovatively introduces new functions such as ATO, automatic turnback, and platform door protection on the basis of the CTCS-2 train control system, achieving the deep integration of technologies in national railway and urban rail transit. This innovation means that there is no precedent for the project construction, especially the commissioning, which is full of unknowns and challenges.

To this end, CASCO has assembled elite forces from Shanghai, Beijing, Wuhan, Kunming, and Suzhou, etc., integrating the team resources in urban rail and national railway to complement each other's advantages and jointly overcome difficulties.

Wang Jianxue, who is responsible for the testing of trackside equipment, has many years of experience in national railway projects, but this is his first time to fully participate in commissioning. He said, "When I first received the commissioning task, I wasn't sure about it. Thanks to the company's rich experience in urban rail commissioning, with the joining of colleagues in urban rail transit, we sorted out a complete commissioning system together, forming a series of normative documents. I also learned a lot personally."

Based on the CTCS-2 technology in national railway, CASCO has compiled the commissioning procedure of signaling system with the characteristics of suburban railway, combining the management method of signaling commissioning in urban rail. The test content exceeds 100 items in total to ensure the safety and reliability of every function of the system. Based on the practical experience of this project, CASCO has further sorted out a set of commissioning system applicable to the CTCS-2+ATO signaling, providing valuable references for the construction of subsequent similar projects.

During the commissioning, the busiest time required uninterrupted train operation for 24 hours a day. Li Guanghua, who is responsible for the testing of urban rail system, introduced that as the signaling system integrator, CASCO not only needs to complete the signaling system testing but also needs to communicate and coordinate for some emergencies or unexpected events in the face of complex field environment. When asked if it was difficult to be "stuck" at the site all day, he and his colleagues said, "Time flies too fast. We actually wish time could slow down a bit so that we can do a more thorough job of testing."

Li Zhiyi, who is responsible for CTC function testing, shared, "Although we tested many times in the lab earlier, it was still moving to see everything working normally on site, such as the automatic trigger of route sequence, the automatic route setting on the station diagram, the automatic tracking of back-and-forth trains, the yellow light band for speed limit issuance, and the report of scheduled line points on the operation diagram. It's like watching a concert live versus in person; it's a completely different feeling," expressing a sense of accomplishment.

This project is the first part of the planned 1,157-kilometer suburban railway blueprint in Shanghai. To leverage its role as a demonstration line, engineers strive for excellence in construction and do not overlook any detail. For example, to improve the parking accuracy of platform doors, they have undergone countless software optimizations and tests, aiming to provide passengers with a more comfortable experience.

Long-term involvement in the frontline of the project has not only honed the professional skills of engineers but also allowed them to make many new friends, including colleagues from clients and other construction units. They have worked side by side and forged deep friendships. Li Guanghua, who has more than 10 years of experience in urban rail commissioning, said that he was surprised to encounter a subway driver he had worked with many years ago on site. "When we met again, we felt very close, and our work coordination was also very tacit."

The summer of 2024 in Shanghai was particularly hot, which was crucial for the project's commissioning. Since the control center had not been equipped with air conditioning in the early stages of construction, the heat generated by equipment operation accumulated in the equipment room. These "sauna rooms" with temperatures above 36°C were a huge test for the engineers.

In stark contrast, some colleagues turned into "underground workers", barely encountering the summer as they left for work early and returned late. Wang Jie, who is responsible for the testing of the centralized signal monitoring system, is one of them. He once joked, "In the summer when everyone turns dark, I turn white. This is the unique magic of the suburban line!" Since entering the underground, his phone couldn't receive signals. When asked curiously about what he did during his frequent "disconnects", Wang Jie always humorously replied, "I'm building a beautiful China in corners you can't see."

This statement is lightly said, but it reveals the deepest confession of CASCO engineers. In the near future, Shanghai Suburban Railway Airport Link Line will officially open. To welcome this milestone moment and create more wonderful travel experiences, CASCO engineers are still striving.