| Topic: | Re:Reply | |
| Posted by: | Michael Robinson | |
| Date/Time: | 17/02/20 16:04:00 |
| GPS doesn't work inside tunnels. I stand to be corrected, but it seems to me that a train needing to frequently switch between different signalling systems would be highly prone to faults and errors. Modern signalling systems do use short range radio communications between equipment on the track and the trains. This compares to old equipment where the signalling is hard-wired on the track and detects the train passing overhead, hence the fixed size of signalling blocks mentioned previously. Even then, the high voltages used for train traction doesn't "play nice" with radio frequencies used for signalling causing interference so there can be a lot of system integration needed to get everything working reliably. I recently read of a case in Singapore where a fault on one train caused interference with another train passing it in a tunnel causing it to stop and it took them a while to figure out what was happening. |