The BBC reports "Satellite fault shuts train doors"
Thanks to qwghlmBlog for alerting us to this astonishing bit of ineptitude in a safety critical system. More details are available in the Brighton Argus report "Satellite system traps passengers on trains"
"They have a selective door opening system on board which takes a combination of GPS satellite signals to tell the train exactly which station it is located at and then ensure only the number of doors that are accommodated on the platform are opened."
"In some locations the GPS signal being received is of a much higher strength than the system it was designed for. This is being addressed by changes to the aerial on each train.
"Sometimes we have had problems with the train not locating itself and thus not opening the doors at all. In this instance the driver has to override the system by telling the train where it is and then giving a manual door release."
So what happens when, in the future, the US government encrypts the GPS signals in a trade dispute with the competing European Union Galileo system or as part of some other econoomic sanctions package ?
What happens when cheap GPS jamming and spoofing equipment hits the market as a result of attempts by vehicle drivers to evade the Transport Secretary Alistair Darling's ill conceived satellite road pricing schemes ?
There must be a dozen existing ways of reliably determining when a train is in a station and the length of the available platform. Why have the designers of this safety critical system aboard railway trains, made them dependent on an external system over which they have no control like GPS, whose weak radio signals can be so easily jammed or spoofed ?