Metro operator upgrades Line 1's signals system after 24 years

Engineers completed the upgrade of Line 1's 6502 electric relay interlocking system to the new computer-based interlocking system on Saturday morning. 
Metro operator upgrades Line 1's signals system after 24 years
Wang Rongjiang / SHINE

The 24-year-old signals system of Metro Line 1, which runs between Shanghai South Railway Station and Shanghai Railway Station, was upgraded in the early hours of Saturday.

“The operation with the new system will be more stable, and the signal of the trains will be more accurate,” said Shi Cong, the Shanghai rail transit maintenance support team's chief engineer of telecommunications and signals. “The departure interval between each train will be shortened from 160 seconds to 120 seconds.”

The upgrade is a simple cutover that switched on the new system after the old system was powered off. The transition from the old telecommunications and signals system into a new one is called a cutover.

The upgrading project took more than two years to prepare and process. “It took us more than two years to lay the cables of the new system in the tunnel of Line 1,” said Shi. “We had only two hours every night after Line 1 stopped its operation, but the total length of cable was 537,782 meters.”

Fu Yu, deputy manager of the telecommunications and signals team, said the previous 6502 electric relay interlocking system had served Line 1 for about 24 years. “Its name came from the year it was designed — 1965,” said Fu.

Explaining how the old system worked, Fu said electrocircuits of the system was embedded under the tracks. “When a train drove in, it weighed on the track, which led to a short circuit of the circuit underneath. The signals light in the control room would therefore turn red, suggesting the presence of a train,” Fu said.

The new signals system is called CBI (computer-based interlocking). “Controlled by a central computer, it will be easier to dispatch trains and to take precautions against accidents,” said Fu.

After the cutover, eight trains performed trial runs between 1:25am and 4am to ensure that the new signals system was working perfectly. 

The Metro operator declared the upgrading project a success after the first train departed from Shanghai South Railway Station at 5:30am on Saturday.

The signals system for Line 1 between Xinzhuang Station and Shanghai South Railway Station will be upgraded in the second half of next year.

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