5 ms·

If they're struggling, they should put a shout out to UK radio hams to help diagnose the problem, they'd get loads of expert help.

DocTomoe 5y ago
Or maybe use something that's less dependent on radio frequency in one of the most populated, thus most frequency-polluted areas on Earth. Radio not always is the best choice, sometimes, cable is worth it.
- matthewmacleod 5y ago
  The issue is interference at the interface between the train and the fixed signalling system. I’m sure you can appreciate the impracticality of building a train to signalling system interface that uses cables!
  - zeristor 5y ago
    You’d have to keep plugging it in.
  - teget 5y ago
    Shouldn't systems Like LZB or ETCS bei mostly protected against radio interference as only the Last section (centimeters) needs to bei transmitted wirelessly? Are they used in the line or did they opt for something else?
    - jonp888 5y ago
      LZB uses cable loops. ETCS can use cable loops, but for full functionality a radio data connection is required.
    - matthewmacleod 5y ago
      Yeah, generally that’s true - it’s certainly not a long-range system. I’m not clear on what the actual problem is at Stratford, but I do know these systems can be quite sensitive and it can be tricky to ensure they operate reliably alongside each other. In the case of Crossrail the core (new tunnels) use CBTC signalling, I think based on Siemens TrainGuard - I think the specification of the project predates ETCS being proven as a viable solution for this particular kind of service. The services leaving Stratford to the East use TPWS/AWS in common with most services on the UK mainline network. The challenge is in the transition between the two systems, as I understand it - anything out of the ordinary and the train will of course come to an immediate halt.
  - micropunk 5y ago
    At first blush I can but thinking a bit further, these are electric trains right? And I know there have been "use your home electricity wiring for network" things around for decades... So can't they use the power cables for comms?
    - matthewmacleod 5y ago
      It’s an interesting idea and not without some merit. Some signalling systems do actually use the rails as a conductor already, although that’s just basically “is there are train on me or not” detection. I’m getting out of my depth, but I’m sure I’ve seen at least one signalling system that uses the track circuit as a data signalling channel to the train to provide in-cab signalling, so I’d guess it’s at least theoretically possible. I’d imagine it would have much the same challenges as radio in practice though - interference from poor connections and ambient noise, not to mention your channel is basically a massive antenna.
heavenlyblue 5y ago
Are you assuming radio hams are better at this than engineers getting paid for it?
- bencollier49 5y ago
  No, but I am assuming that in their multiplicity and range of interests, they might quickly stumble on a solution in a way which a smaller population of well-trained professionals wouldn't. Reminds me of Feyerabend's "Against Method".

DocTomoe 5y ago

Or maybe use something that's less dependent on radio frequency in one of the most populated, thus most frequency-polluted areas on Earth. Radio not always is the best choice, sometimes, cable is worth it.

matthewmacleod 5y ago
The issue is interference at the interface between the train and the fixed signalling system. I’m sure you can appreciate the impracticality of building a train to signalling system interface that uses cables!
- zeristor 5y ago
  You’d have to keep plugging it in.
- teget 5y ago
  Shouldn't systems Like LZB or ETCS bei mostly protected against radio interference as only the Last section (centimeters) needs to bei transmitted wirelessly? Are they used in the line or did they opt for something else?
  - jonp888 5y ago
    LZB uses cable loops. ETCS can use cable loops, but for full functionality a radio data connection is required.
  - matthewmacleod 5y ago
    Yeah, generally that’s true - it’s certainly not a long-range system. I’m not clear on what the actual problem is at Stratford, but I do know these systems can be quite sensitive and it can be tricky to ensure they operate reliably alongside each other. In the case of Crossrail the core (new tunnels) use CBTC signalling, I think based on Siemens TrainGuard - I think the specification of the project predates ETCS being proven as a viable solution for this particular kind of service. The services leaving Stratford to the East use TPWS/AWS in common with most services on the UK mainline network. The challenge is in the transition between the two systems, as I understand it - anything out of the ordinary and the train will of course come to an immediate halt.
- micropunk 5y ago
  At first blush I can but thinking a bit further, these are electric trains right? And I know there have been "use your home electricity wiring for network" things around for decades... So can't they use the power cables for comms?
  - matthewmacleod 5y ago
    It’s an interesting idea and not without some merit. Some signalling systems do actually use the rails as a conductor already, although that’s just basically “is there are train on me or not” detection. I’m getting out of my depth, but I’m sure I’ve seen at least one signalling system that uses the track circuit as a data signalling channel to the train to provide in-cab signalling, so I’d guess it’s at least theoretically possible. I’d imagine it would have much the same challenges as radio in practice though - interference from poor connections and ambient noise, not to mention your channel is basically a massive antenna.

heavenlyblue 5y ago

Are you assuming radio hams are better at this than engineers getting paid for it?

bencollier49 5y ago
No, but I am assuming that in their multiplicity and range of interests, they might quickly stumble on a solution in a way which a smaller population of well-trained professionals wouldn't. Reminds me of Feyerabend's "Against Method".