Beijing subway safe from Wi-Fi router signals

Beijing Subway Company Monday said the capital's subway lines have not encountered any operational problems caused when passengers attempt to connect to external Wi-Fi routers, after media reports said it resulted in the malfunction of Shenzhen metro lines last Thursday.

Jia Peng, spokesman for Beijing Subway Company, which runs 15 out of the city's 17 subway lines, said he doubted the truth of the reports.

"So far, there have been no similar cases on Beijing's subway," Jia said.

Beijing's subway system shares the same Communications-Based Train Control (CBTC) signal control system with Shenzhen metro lines, according to Jia.

"The CBTC signal system is a developed and mature radio telecommunication technology that is widely adopted on most metro lines in the world," Jia said. But he did not know whether Wi-Fi signals could affect a train's signal.

Many trains on the Shekou line of Shenzhen subway were brought to an emergency stop last Thursday between 8:15 am to 9:30 am, as the control signal was affected by undefined outside signals, the Shenzhen Metro Company posted on its microblog.

An operator at the Shenzhen Metro's hotline said the reason for the subway signal problem was still under investigation, and she has not received any notice to warn passengers not to bring any wireless equipment on the trains.

But experts in Beijing believe Wi-Fi signals could pose a threat to the operation of subway trains.

Zhao Da, section director of Beijing Radio Administration Bureau, said that the subway's control signal and the Wi-Fi signal are on the same spectrum.　

"So it is possible to affect the subway's control signal although the subway's signal is coded," Zhao said.

Cellphone 3G signals will not affect the subway's signal, as they use a different frequency, he said.

Zhao suggested wireless routers should not be used on trains for safety.