6 ms·

Because of signal sighting rules in the UK, we experienced a lot of trouble upgrading lines to higher speed. All of a sudden, that signal that you could see for

Because of signal sighting rules in the UK, we experienced a lot of trouble upgrading lines to higher speed. All of a sudden, that signal that you could see for 10 seconds could now only be seen for 8 due to a bridge or whatever. Muchos dollars relocating signals and in some places not being able to increase the line speed at all. Boring but very real reasons why we "can't just update things"

red_admiral 8y ago
And of course there's the whole discussion in the UK about having a second safety-critical person on the train (e.g. "guard", "train manager" etc.) versus driver-only operation.
TylerE 8y ago
Dunno why they don't just go ahead and bite the bullet and go to 100% in-cab signaling. The technology has worked for decades and has been deployed on many lines, including a few in the UK.
- kposehn 8y ago
  Cab signaling requires a different set of standards in order to provide the necessary level of safety. Cab signals are (usually) transmitted through the rail and picked up by a special receiver on the leading axle of the locomotive. Each locomotive has to be equipped and the rails themselves have to be checked and blocked. This also means the rails have a higher maintenance requirement as opposed to lineside signals which can be more easily maintained. However, some countries (Brazil predominantly) have embraced a GPS based cab signal system where lineside signals are almost totally eliminated. However, this was done with federal subsidies to cover the expense iirc. Another example is the US Northeast Corridor where cab signals are used along with lineside signals to provide a level of redundancy at speed. Unfortunately there’s no easy solution, but I lean towards the Brazilian GPS based systems from Wabtec.
  - ComradeTaco 8y ago
    As a random piece of trivia, in cab signaling was pioneered in the 1920's and implemented commercially by Pennsylvania Railroad the 1930's while upgrading their main line between New York City and Washington D.C. You can see in this photo that the engineer had one indicator that would light up for each signal aspect: https://i.pinimg.com/originals/31/85/83/3185833fba11b79498ff9c658e730fc4.jpg https://i.pinimg.com/originals/31/85/83/3185833fba11b79498ff...
  - gsnedders 8y ago
    Realistically, in the UK, it's going to be ETCS with balises: all new build stock at this point either has ETCS in-cab signalling fitted, or is designed for its fitment. That said, the rollout of the infrastructure side of ETCS is somewhat delayed, but it is happening in places (Thameslink is ETCS Level 2 with conventional signal overlay, albeit with shorter blocks in ETCS; Crossrail is ETCS Level 2 with no overlay).
- adrianN 8y ago
  You'd have to upgrade all the rolling stock as well. That's not always possible, for technical or financial reasons.
  - TylerE 8y ago
    The locomotives, not all the rolling stock. I'm not saying it wouldn't be hard/expensive, but it seems better to spend money on things that will be useful for decades rather than stopgaps that just kick the can a little further up the road.
    - adrianN 8y ago
      You're right of course, just the locomotives. If budgets always allowed us to do what's best over the next decades the world would probably be a much nicer place.
    - eponeponepon 8y ago
      But when the people who hold the pursestrings are looking no further ahead than their next election, "useful for decades" means nothing at all to them.
    - donarb 8y ago
      If you remove the block signaling system and use in-cab signaling, you still need to know where the back of the train is. Otherwise a train could run into the back of another in the fog or heavy rainstorm. Currently, railroads use FREDs (flashing rear end device) on the last car of the train. Some FREDs are more intelligent than others but would benefit from being able to send out their location via GPS. https://en.wikipedia.org/wiki/End-of-train_device https://en.wikipedia.org/wiki/End-of-train_device
      - Retric 8y ago
        Longest trains are under five miles so you could use that or whatever the limit for that line is as a safe baseline. Unless you're worried about trains separating.
ant6n 8y ago
How about using some sort of advance signal?
- gsnedders 8y ago
  There are repeater signals for this purpose, see http://railsigns.uk/sect7page1/sect7page1.html http://railsigns.uk/sect7page1/sect7page1.html
maxerickson 8y ago
The DOT here just updated the signaling at some road intersections and I've really appreciated the better visibility.

red_admiral 8y ago

And of course there's the whole discussion in the UK about having a second safety-critical person on the train (e.g. "guard", "train manager" etc.) versus driver-only operation.

TylerE 8y ago

Dunno why they don't just go ahead and bite the bullet and go to 100% in-cab signaling. The technology has worked for decades and has been deployed on many lines, including a few in the UK.

kposehn 8y ago
Cab signaling requires a different set of standards in order to provide the necessary level of safety. Cab signals are (usually) transmitted through the rail and picked up by a special receiver on the leading axle of the locomotive. Each locomotive has to be equipped and the rails themselves have to be checked and blocked. This also means the rails have a higher maintenance requirement as opposed to lineside signals which can be more easily maintained. However, some countries (Brazil predominantly) have embraced a GPS based cab signal system where lineside signals are almost totally eliminated. However, this was done with federal subsidies to cover the expense iirc. Another example is the US Northeast Corridor where cab signals are used along with lineside signals to provide a level of redundancy at speed. Unfortunately there’s no easy solution, but I lean towards the Brazilian GPS based systems from Wabtec.
- ComradeTaco 8y ago
  As a random piece of trivia, in cab signaling was pioneered in the 1920's and implemented commercially by Pennsylvania Railroad the 1930's while upgrading their main line between New York City and Washington D.C. You can see in this photo that the engineer had one indicator that would light up for each signal aspect: https://i.pinimg.com/originals/31/85/83/3185833fba11b79498ff9c658e730fc4.jpg https://i.pinimg.com/originals/31/85/83/3185833fba11b79498ff...
- gsnedders 8y ago
  Realistically, in the UK, it's going to be ETCS with balises: all new build stock at this point either has ETCS in-cab signalling fitted, or is designed for its fitment. That said, the rollout of the infrastructure side of ETCS is somewhat delayed, but it is happening in places (Thameslink is ETCS Level 2 with conventional signal overlay, albeit with shorter blocks in ETCS; Crossrail is ETCS Level 2 with no overlay).
adrianN 8y ago
You'd have to upgrade all the rolling stock as well. That's not always possible, for technical or financial reasons.
- TylerE 8y ago
  The locomotives, not all the rolling stock. I'm not saying it wouldn't be hard/expensive, but it seems better to spend money on things that will be useful for decades rather than stopgaps that just kick the can a little further up the road.
  - adrianN 8y ago
    You're right of course, just the locomotives. If budgets always allowed us to do what's best over the next decades the world would probably be a much nicer place.
  - eponeponepon 8y ago
    But when the people who hold the pursestrings are looking no further ahead than their next election, "useful for decades" means nothing at all to them.
  - donarb 8y ago
    If you remove the block signaling system and use in-cab signaling, you still need to know where the back of the train is. Otherwise a train could run into the back of another in the fog or heavy rainstorm. Currently, railroads use FREDs (flashing rear end device) on the last car of the train. Some FREDs are more intelligent than others but would benefit from being able to send out their location via GPS. https://en.wikipedia.org/wiki/End-of-train_device https://en.wikipedia.org/wiki/End-of-train_device
    - Retric 8y ago
      Longest trains are under five miles so you could use that or whatever the limit for that line is as a safe baseline. Unless you're worried about trains separating.

ant6n 8y ago

How about using some sort of advance signal?

gsnedders 8y ago
There are repeater signals for this purpose, see http://railsigns.uk/sect7page1/sect7page1.html http://railsigns.uk/sect7page1/sect7page1.html

maxerickson 8y ago

The DOT here just updated the signaling at some road intersections and I've really appreciated the better visibility.