The world’s first rail transit “dual signal system” will be appliedin Shanghai Metro
After nearly five years of continuous technical research and transformation, the signal control system transformation of Shanghai Rail Transit Line 2 has achieved a key breakthrough recently. After the installation and commissioning of 31 newly purchased trains, the reconstruction project of the signal of 69 existing trains have been also officially started. In the future, Line 2 will be upgraded with the world’s first “dual signal system”. Even if the main signal system encounters a failure, its backup system can still achieve a 2-minute train operation interval to ensure normal operation during peak hours.
As an important line that runs through the city center and connects the two major airports in Shanghai, Line 2 has an average daily passenger flow of about 1.5 million passengers, and it can reach 2 million passengers on a peak day. It ranks first in the average daily passenger flow of the entire network. The characteristics of large passenger flow put forward extremely high requirements on the stability and safety of Line 2 operation.
According to reports, as early as 2014, the Shanghai Metro began to study the signal renewal and transformation plan for Line 2. At that time, there were two traditional transformation schemes in front of the technicians: the first was to use the original signal system, and the second was to replace it with a new system. The original signal system of the first scheme has been unable to meet the growing passenger demand of Line 2. The second new alternative requires that all equipment and trains on the entire line must complete the synchronous cutover of the new system in one night. For Line 2 with a long line and many trains, the workload is huge and the potential risks are high. It is an almost impossible task. In addition, Line 2 is divided into four phases and opened for operation. The equipment life cycle of each section is not uniform. In order to update the oldest part of the equipment, most of the equipment that has not yet expired is also updated. A waste of upfront investment. In addition, the most important thing is that as the line with the largest passenger flow in the entire network, Line 2 cannot withstand the drastic drop in operating efficiency caused by the failure of the main system.
After repeated exploration and derivation, Shanghai Metro has made a breakthrough in putting forward a third transformation plan for high operating pressure, segmented openings, and a large amount of equipment-the “dual signal system”. The “dual signal system” is expected to solve the problem that Line 2 needs to be retrofitted in one fell swoop, and the construction period will be shortened by more than one year. Even if the main signal system fails or the signal is degraded, the backup system of the modified system can still meet 2 minutes operating interval requirement greatly reduces the impact of signal failure on operations, and the cost of transformation has also been greatly reduced.
Since 2015, centering on the goal of “dual signal systems”, Shanghai Metro and Casco Signal Co., Ltd. and other Chinese first-class companies have jointly formed a project team, with domestic and foreign technical experts, finally successfully completed the on-board test of the CBTC+TBTC compatible on-board system, and successfully passed the third-party safety certification.
However, greater challenges are still in the subsequent system transformation process, especially to achieve seamless integration between two signal systems of different ages, different standards, different manufacturers, and different designs, so as to ensure that trains can realize self-control between different systems. Adapting to mixed operation is equivalent to mastering two “languages” for each train to achieve “barrier-free bilingual communication.”
In September 2019, some of the newly purchased trains on Line 2 were successfully put into operation with a new compatible system, successfully ensuring the smooth operation of Line 2 under high passenger pressure during the second CIIE, thus completing the “dual signal systems” had successful application in the first time in the world. At present, the installation, commissioning and online operation of 31 newly purchased trains on Line 2 have been successfully completed, the retrofitting and commissioning of 69 existing signal trains has officially started, and newly added equipment at the station has also been installed.
According to the system design, the related performance of Line 2 system has been improved exponentially after it was put into operation. For example, the operating efficiency has been greatly improved, and the designed operating interval is 90 seconds, which can ensure that 30 trains open in opposite directions per hour and achieve a rapid return in 2 minutes. According to relevant data analysis, the time from automatic door closing to automatic departure of the new system is about 11 seconds. The station can save 15 seconds of effective stop time, and the train departure time has increased from an average of about 360 seconds to about 120 seconds. In addition, the train tracking interval will be shortened from the original 150 seconds to 120 seconds.