Platform sharing & permissive working

[fil]

Hi,
Am I right in thinking that permissive working is not an acceptable means of working for anything other than coupling trains?
If so, how do we control platform sharing? Signals mid platform seems the obvious solution but how would one get the required overlap?

Thanks

[Jerry1237]

Permissive working is not permitted for moves under a main aspect. However, using a call-on route, a passenger train can enter an occupied section under a subsiduary aspect and their exit signal is effectively the obstruction (i.e tail light, back end of train, buffer stops, other red aspect in the route).

Here are some homework questions for you:
1) what is the difference between a warner, call-on, main and shunt route?
2) which type of route in 1) can a passenger train not use?
3) which type of route in 1) can a freight train not use?

Answers to this forum within five days please (except for PJW).

Jerry

[Peter]

Hi,
Am I right in thinking that permissive working is not an acceptable means of working for anything other than coupling trains?
If so, how do we control platform sharing? Signals mid platform seems the obvious solution but how would one get the required overlap?

Thanks

If you are looking at how permissive platform working has been used rather than what is stated as preferred today, have a look at places like the main London termini (Paddington, Waterloo etc) or at places where services start / terminate / divide en route (Eastleigh, Haywards Heath spring to mind). Bristol Temple Meads is an interesting case study on platform sharing because of the way the route indicator effectively gives the driver the authority (or not) to pass the mid platform "signal" which never changes its indication.

If you can find out about how it has been used, you will appreciate some of the risks that may be present and see why is may not be appropriate for general use, but if the relevant risks can be controlled, perhaps not ruled out totally.

[PJW]

Yes you are broadly correct; the ambition is not to have permissive passenger working except when it is unavoidable due to the timetable requirement to join two trains together and go forward as one (saves train crew and even more important increases capacity as only utilise the one train path in a congested area).

However historically it was regarded as perfectly acceptable, and in truth there have been very few accidents and incidents because of it. At some places there wouldn't be enough platforms to keep to the rule, one train in one platform. Sometimes, subject to risk assessment, it is possible to argue for the perpetuation of permissive moves at a particular site. Other places have got mid-platform signals- I think of Manchester Piccadilly through platforms on the line to Oxford Road and Birmingham New Street. Such places do tend to have very short overlaps, in the range 20m to 50m; even so rather better than the tail lamp of the previous train that has a zero overlap.

In some places (pretty sure The Netherlands is one) the platform staff wheel out on the platform a portable stop marker signal that if battery fed from the platform trolley on which it is mounted- this tells the incoming train driver exactly where to stop (and thus choose an appropriate overlap for the circumstances) and once it has served its purpose they wheel it away again.

I don't know the history of the BTM mid platform markers (i.e. whether they pre-date the current signalling that I believe dates from the late 1960s/ early 1970s); not sure they are actually unique, but cannot think of an equivalent elsewhere. Not in the Rule Book but I guess in some local operating instructions; very Western Region- cheap and simple and serves the purpose, so can't see it being adopted as a national standard.

As Peter said, there is less concern about terminal platforms particularly if the approach visibility is good. It is all about controlling risk and balancing any theoretical increase in safety against deteriorating flexibility and operability. If we don't signal the second train into the same platform somehow, then it'll probably just have to be held at a red signal and potentially cause delay to other trains as well as itself. This itself has a safety consequence; more trains being brought to red signals means more opportunity for a SPAD to occur.......

Hi,
Am I right in thinking that permissive working is not an acceptable means of working for anything other than coupling trains?
If so, how do we control platform sharing? Signals mid platform seems the obvious solution but how would one get the required overlap?

Thanks

If you are looking at how permissive platform working has been used rather than what is stated as preferred today, have a look at places like the main London termini (Paddington, Waterloo etc) or at places where services start / terminate / divide en route (Eastleigh, Haywards Heath spring to mind). Bristol Temple Meads is an interesting case study on platform sharing because of the way the route indicator effectively gives the driver the authority (or not) to pass the mid platform "signal" which never changes its indication.

If you can find out about how it has been used, you will appreciate some of the risks that may be present and see why is may not be appropriate for general use, but if the relevant risks can be controlled, perhaps not ruled out totally.

[fil]

Permissive working is not permitted for moves under a main aspect. However, using a call-on route, a passenger train can enter an occupied section under a subsiduary aspect and their exit signal is effectively the obstruction (i.e tail light, back end of train, buffer stops, other red aspect in the route).

Here are some homework questions for you:
1) what is the difference between a warner, call-on, main and shunt route?
2) which type of route in 1) can a passenger train not use?
3) which type of route in 1) can a freight train not use?

Answers to this forum within five days please (except for PJW).

Jerry

1) main route:
main aspect entrance signal
main aspect exit signal
full overlap

warner route:
main aspect entrance siganl
main aspect exit signal
overlap can be reduced to 50m dependant on the amount of delay applied to the approach control of the entrance.

call on route:
entrance= PLG associated with a main aspect showing two white lights at 45 Degrees.
no exit signal (train)
no overlap
used under permissive working so track section to be occupied in route.
speed to be limited to stopping distance.
approach control of entrance to bring train to a stand before a movement aurthority is given.

shunt route:
entrance= PLG two white lights 45 deg
exit= PLG two red
overlap can be reduced to 47m
not permitted for passenger moves. (answer2)

3) ?????freight trains cannot use call on routes?????
i can't think of any benefits in allowing a freight train to approach an occupied passenger platform.


wasn't sure how much detail you were looking for, this is just a quick sum up.

[Jerry1237]

@fil

Basically, yes. I believe there are a couple details that differ between our answers.

1)
Main - route from main aspect to main aspect with full overlap.
Warner - main aspect to main red aspect (at time of release?) with reduced overlap and approach release
Call-on - PLI to clear of obstrution or red aspect, permissive move with effectively no overlap.
Shunt - Non-passenger move (2) from PLI to clear of obstruction or red aspect with potentially no overlap.

Only other comment I'd make is about speeds. With main aspects the speed is what is appropriate but not exceeding the local speed restrictions or speed of the line, whichever is greater. With the rest, shunt is walking pace (<15mph!) and warner/call-on/shunt mandate such a speed as to be able to stop the train clear of any obstruction, i.e. with caution (if you read a lot of accident reports for yards, approaches to terminals etc., caution is often not exercised).

3) Why can't non-passenger trains use a call-on? Imagine a station used for berthing trains overnight. An MPV turns up and needs a turnback move. Possibly no shunt move available... (PJW or Peter may correct me on this).

4) Level of detail is whatever is appropriate for you. Our hope is that people learn from the forum by asking even the most daft question and then researching the answer or getting peer advice. Good to see someone rising to a challenger. Well done.

Jerry

[PJW]

It depends on route knowledge and circumstances.

I believe a freight train is permitted on a call-on move; the issue is that we would not want to signal a freight train on top of a passenger train waiting in the platform. The signaller is permitted to use the signal (at some stations) as a Permissive Passenger but not by regulations allowed to use for a freight. However there is no interlocking that would prevent and the driver wouldn't know better and so would take the aspect.
The signaller I believe can use permissively for two freight trains to share the section; indeed there are call-on moves rovided on non-passenger railway.

Note that an Empty Coaching Stock train (and I think also a light loco which could be regarded as an ECS with zero coaches) can be counted as eighther "freightr" or "passenger" as convenient to the situation.

@fil

Basically, yes. I believe there are a couple details that differ between our answers.

1)
Main - route from main aspect to main aspect with full overlap.
Warner - main aspect to main red aspect (at time of release?) with reduced overlap and approach release
Call-on - PLI to clear of obstrution or red aspect, permissive move with effectively no overlap.
Shunt - Non-passenger move (2) from PLI to clear of obstruction or red aspect with potentially no overlap.

Only other comment I'd make is about speeds. With main aspects the speed is what is appropriate but not exceeding the local speed restrictions or speed of the line, whichever is greater. With the rest, shunt is walking pace (<15mph!) and warner/call-on/shunt mandate such a speed as to be able to stop the train clear of any obstruction, i.e. with caution (if you read a lot of accident reports for yards, approaches to terminals etc., caution is often not exercised).

3) Why can't non-passenger trains use a call-on? Imagine a station used for berthing trains overnight. An MPV turns up and needs a turnback move. Possibly no shunt move available... (PJW or Peter may correct me on this).

4) Level of detail is whatever is appropriate for you. Our hope is that people learn from the forum by asking even the most daft question and then researching the answer or getting peer advice. Good to see someone rising to a challenger. Well done.

Jerry