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ARS question

Current and future British signalling (UK except Northern Ireland)

ARS question

Unread postby Mike Stone » Mon Apr 17, 2017 3:07 pm

I recently noticed on the open train times map a train arrived in platform 4 at Stafford. Normally the route behind it would disappear, but in this case it didn't.
;
Would this be due to ARS selecting the route for a following train?
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Re: ARS question

Unread postby RDNA » Tue Apr 18, 2017 11:00 am

Post by Mike Stone » Mon Apr 17, 2017 3:07 pm

I recently noticed on the open train times map a train arrived in platform 4 at Stafford. Normally the route behind it would disappear, but in this case it didn't.
;
Would this be due to ARS selecting the route for a following train?


No Mike, currently ARS cannot 'overcall' routes, what you saw was probably caused by the signaller operating an AUTO facility for the next train to follow.

This lack of overcalling causes problems where signals on approach to a conflicting point have 'Double Red' controls (for TPWS overspeed purposes) i.e. the next signal in rear is approach controlled unless a 'live' route is set from the protecting signal.

DB
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Re: ARS question

Unread postby rower40 » Tue Apr 18, 2017 8:01 pm

RDNA wrote:
No Mike, currently ARS cannot 'overcall' routes, what you saw was probably caused by the signaller operating an AUTO facility for the next train to follow.

This lack of overcalling causes problems where signals on approach to a conflicting point have 'Double Red' controls (for TPWS overspeed purposes) i.e. the next signal in rear is approach controlled unless a 'live' route is set from the protecting signal.

DB

I've configured ARS to overset routes in specific cases where it allows the previous signal to clear to an unrestricted yellow instead of being approach-controlled-from-red. Great Eastern, Down Main through Seven Kings springs to mind as an example.
It's important to ensure that the route releases after one train before letting ARS set it for the next one, but the first train does not have to have left the section. Also ARS has to be configured to ignore the fact that the route has not proved within the usual 30-second route proving timer.
I agree that what was seen by the original poster was most likely the use of an A-button.
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Re: ARS question

Unread postby Mike Stone » Mon Apr 24, 2017 1:45 pm

Thanks - I had subsequently come to that conclusion, and wondered if it was being done to stop ARS crossing trains slow to fast through platform 3, with nothing approaching UF, which makes little sense.
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Re: ARS question

Unread postby StevieG » Mon May 8, 2017 10:48 am

Not sounding like a similar situation in that no oversetting of route was involved, but in case of interest, just thought I'd mention about the ability of ARS to request the setting of route into an occupied terminal platform.

From the outset at Liverpool Street (1989), I recall that ARS was able to request the SSI to set Call-On class route into an occupied platform in at least two circumstances : -

- If the data for the approaching train in the TTP (TimeTable Processor) contained a next working's train description (TD), known as its "Association", which matched that already interposed for another train already in an accessible platform [whether done by ACI (Automatic Code Insertion) or manually by the signaller], then ARS would request the route into that platform for the second train, as an attaching of the two trains was apparently required ; OR

- If the TTP data of the approaching train included a "J" (Join) data instruction with the TD of another train already in a platform, then, again, route into the occupied platform would be requested by ARS.

Whether and at what point, the signal was permitted to display the call-on aspect for the second train was a different matter, separate from ARS operation, and dependent on the absence, or presence (and to what degree), of train-length measuring track detection sections in the platform(s) and at the signal's approach ('Lime Street' Control or similar), any provision of a 'Lime Street' override facility, etc.

Afraid I have no experience of ARS being configured to handle attaching / detaching or 'platform sharing' at through stations' platform lines, so do not know how such may be facilitated.
BZOH

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