Recently, several subway trains in Shenzhen, Guangdong province, have been suspended due to interferences from passengers' portable Wi-Fi devices. Passengers are not responsible for the technical problems and have the legal right to use the free and publicly available 2.4-gigahertz radio frequency, says an article on The Beijing News. Excerpts:

An investigation revealed that subway lines in Shenzhen have adopted the advanced railway signaling system known as Communication Based Train Control System, or CBTC, which can be affected by interfering signals.

Though other major cities in China haven't updated their subway systems with the CBTC system, in the long run many cities are also bound to face similar problems.

Metro operators in Shenzhen called for a ban on the usage of Wi-Fi enabled 3G devices. That's understandable due to safety reasons, but in the long run, it is the subways' responsibility to find ways to solve the issue.

Some suggest that subway systems need to apply for different radio frequencies. However, as we enter the information age, radio spectrums have become precious strategic resources and some national frequencies are being auctioned for billions of US dollars. Subways can hardly afford this.

Subways in other Chinese cities should take Shenzhen's incidents as a lesson and build "wireless metro" services, to provide passengers with free Wi-Fi services.

Subways abroad using the CBTC system should also take note as they're facing potential safety hazards.