Metro Line 1, one of the oldest and busiest lines of Mexico City, has been in operation since 1969. The line spans 18.83 kilometers and has 20 stations, with daily passenger volume exceeding 1 million.

The subway overhaul is CRRC's first overseas "system plus" project. It involved investment, financing, manufacture of new trains, comprehensive modernization, and upgrade of existing car communication and signaling systems, electromechanical systems and the maintenance system.

The upgraded metro line is now equipped with a communication-based train control system, which offers more precise train control, better service reliability and increased route capacity, the company said.

CRRC Zhuzhou founded a local factory in Mexico City to make train cars. So far, 15 cars have been manufactured, with the help of more than 100 local suppliers. It has also trained nearly 300 Mexican technicians and created some 1,500 jobs for the local people.

The company has developed rubber wheel train cars for the subway line, which are safer, need less energy and produce less noise. Each such train has nine carriages, a capacity to carry 2,252 people and can reach a top speed of 80 kilometers per hour.

Wang Qiaolin, general manager of CRRC Zhuzhou, said the city government, its metro bureau, the Chinese embassy in Mexico and local partners extended support to the project, contributing to its success.

The company will now strengthen its communication with different sides to make sure the upgrade of the second section of the line is completed on time, he said.

Marti Batres, mayor of Mexico City, said the metro is an indispensable part of people's daily lives in the city and integral to urban culture.

Apart from the locations of the subway stations, which stay the same like on the old line, all other things of the upgraded Line 1 are new, which will offer a more comfortable experience to passengers, he said.

Hector Villanueva, who works for CRRC Zhuzhou's unit in Mexico, said he is proud to be part of the company and participating in the upgrade project.

The upgraded line is modern and offers smooth train rides, comfort and safe service to local people, he said.