Replacing signals when a train is approaching

What happens if a yellow ground signal reverts and gets passed?

Would this be a SPAY?

Crikey, I started something here! X

I can also replace a signal at any time providing the driver of an approaching train doesn't see an adverse change of aspect OR if the driver of an approaching train will see an ACOA, I have to forewarn the driver that this is what I am going to do. I don't have to wait until the train is at a stand at the signal I wish to replace before doing so. Providing the driver is aware that I'm doing it, it's ok to do so. There is also a prevalence for some signalmen to ask the driver's "permission" to replace the signal. This is absolutely not the case. The Driver does not have that authority. In the hierarchy of Safety Critical Communications (for which these situations would be classified) the Signalman is only subordinate to the Electrical Controller. The Driver, and anyone else, is therefore subordinate to the Signalman.

" said:

What happens if a yellow ground signal reverts and gets passed?

Would this be a SPAY?

Depends on the lay of the points? If they're toward the main line then that would still be a SPAD, if they're away from it then it's not anything.

What happens if a yellow ground signal reverts and gets passed?

Would this be a SPAY?

Earlier i had an AHB failed indication just as a train was approaching it. I hit the emergency replacement and got docked points for it. :S

Aren't AHB failures usually when the barriers have been *down* for too long? I don't know for sure, I'm not a signaller... but it could be the train heading towards it was just much slower than usual for that line or something?

Wrong side failures are very rare (though not absolutely unheard of), but I'm struggling to think of a single failure mode where you'd end up with no red road lights *and* the barriers up *and* a failed indication in the box

Wouldn't the train have to stop and protect (flag) across the malfunctioning crossing anyway unless the failure had been ascertained positively to be 'right side' (i.e. barriers stuck down), and perhaps even in that case (depending on operating rules)?

Interesting note about US practice: I know of no facility (either local or remote) on gated level crossings in the US akin to the functional/failed indications provided either locally or remotely on active level crossins in the UK. Then again: what's this about treadles and such being used to actuate level crossings? I'd think you'd want different strike-ins for HSTs and class 8 freights... :huh: (Or equivalently: does the UK make use of constant warning time or predictor-type detectors at automatic level crossings?)

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Wrong side failures are very rare (though not absolutely unheard of), but I'm struggling to think of a single failure mode where you'd end up with no red road lights *and* the barriers up *and* a failed indication in the box

Leaving barriers in local control!

Ff

Quote:

Wrong side failures are very rare (though not absolutely unheard of), but I'm struggling to think of a single failure mode where you'd end up with no red road lights *and* the barriers up *and* a failed indication in the box

Leaving barriers in local control!

Ff

I don't know if there are systems that don't have a TRTS button but just do it based on average timing for dwell times - anyone know?

I don't think it would be unreasonable for a real signaller to cancel a route with a train approaching for an AHB failure, but not sure what the exact rules are.

It would probably be a disproportionate effort on the part of Geoff and Clive to alter the core code to prevent a penalty in these circumstances.

Warning time is constant. AHBs are generally twenty-seven seconds from the crossing sequence starting to the train passing over the crossing if it is doing line speed.

Treadles are used in conjunction with track circuits for this purpose.

One thing we do have (which you may have noticed in some sims) is, where an AHB is very close to a station, the signaller has to specify whether the train is stopping or not. For stopping trains, barrier sequence is delayed until a TRTS button is pressed (at which point the protecting signal at the station will clear) - for non-stopping trains, the sequence starts in the usual place for such crossings (before the station).

I don't know if there are systems that don't have a TRTS button but just do it based on average timing for dwell times - anyone know?

" said:

Warning time is constant. AHBs are generally twenty-seven seconds from the crossing sequence starting to the train passing over the crossing if it is doing line speed.

Treadles are used in conjunction with track circuits for this purpose.

That's not quite accurate or, more precisely, it's misleading.

The strike-in point for the crossing is 27 seconds (on single lines; 37 seconds on double lines, but the crossing doesn't activate for 10 seconds) *at line speed* from the crossing. 50% of trains should arrive within 50 seconds and 95% within 75 seconds of the start of the sequence. If this can't be met, *then* a predictor system or speed discrimination controls need to be installed. SimSig doesn't have either of these, though it might be possible to simulate speed discrimination controls with some special logic - I haven't looked into it.

Waterbeach doesn't have a TRTS plunger but a seperate set of 'treadles' which become active when 'stopping' is selected. Once the train departs the station and activates this treadle the barrier sequence starts and the signal clears after about 15 seconds.