Interlocking Systems
This invention relates to a method of applying interlocking logic, an interlocking for a railway track and railway systems.
More particularly, the invention relates to interlocking of railway trackside signalling equipment, in particular, to interlocking of railway trackside signalling equipment on lines where different trains can be supervised in different ways by on-board signalling equipment. It also applies to lines on which a given train can be supervised in different ways at different times.
Specifically the invention relates to interlocking of railway trackside signalling equipment on lines where movement authorities are presented to trains, and supervised by signalling equipment on-board these trains, in different ways.
Background
By way of introduction, "railway trackside signalling equipment" is that equipment which authorises train movements on railway lines. "Interlocking" is the functionality within this equipment that ensures movement authorities are only given when it is safe to do so.
The trackside signalling equipment applies interlocking logic to determine whether to authorize a train to enter a specific signalling route. This equipment selects between different interlocking logic according to whether the next train to enter the route is supervised by on-board signalling equipment in a specific way, suitable methods / systems for this selection being known in the art.
As is well-known in the art, various signalling architectures are available within the field of rail signalling. Fig. 1 schematically shows two such architectures, here referred to as "System A" and "System B". It will be understood that only one such architecture will be used to authorize train movements at a given time, and in Fig. 1 these architectures are shown with the same train 1 to provide clear comparison only.
Both Systems A and B comprise trackside (i.e. located proximate track 2) equipment 3A and 3B respectively, installed on the railway infrastructure. System B trackside equipment 3B provides information directly to the train driver 4 whereas System A trackside equipment 3A does not. Both sets of trackside equipment 3A, 3B are controlled by interlocking equipment 5, which also received inputs from fail safe train detection equipment 6.
System A includes equipment 7A on-board the train; this equipment 7A provides information to the driver and interfaces to train traction and / or braking equipment (shown generally at 8). System B may also have such on-board equipment 7B.
Both System A and System B inform the train driver 4 him how far and how fast the train is authorized to proceed, as determined by interlocking equipment 5. System A presents this information to the driver 4 from a display (not shown) within the driving cab, and this is known as 'cab signalling'. System B presents the information to the driver 4 from components of its trackside equipment 3B, known as 'signals'. System B may supplement this information from signals with information presented within the driving cab.
System A cuts traction and / or applies brakes if the train 1 travels further or faster than is safe. This is known as 'Automatic Train Protection (ATP)'. System B may also optionally provide ATP functionality.
An example of the application of this invention is where System A comprises European Train Control System (ETCS) Level 2 / ETCS Level 3 and System B comprises colour light signals.
In this case, trackside equipment 3A comprises a device known as a Radio Block Centre (RBC). System A ETCS movement authorities are issued via radio from the RBC 3A to the train. These ETCS movement authorities are processed by ETCS on-board equipment 7A and presented to the driver as cab-signalling information. The ETCS on-board equipment 7A also provides ATP functionality by supervising train speed such that the train never travels further nor faster than authorized in its
ETCS movement authorities.
A further example of the application of this invention is where System A comprises Communication Based Train Control (CBTC) and System B comprises colour light signals. The benefits and functionality work in a similar way to that for ETCS Level 2 / ETCS Level 3 described above.
In general, System A can be viewed as any signalling system which provides movement authorities and utilises cab-signalling, while System B may be any signalling system which relies upon trackside signals rather than cab-signalling.
Trains signalled by System A can operate on the same railway line as trains signalled by System B. However, because System B trackside equipment presents information directly to drivers, System B information is also presented to drivers of trains operating under System A. A key requirement for such mixed traffic operation is that this System B information does not contradict that which the driver receives from System A.
The interlocking conditions for authorizing train movements can be less restrictive for trains operating under System A than for those operating under System B. This is principally because System A does not suffer from the constraints associated with presenting information to drivers from trackside equipment. Furthermore, System A provides ATP supervision, which can be used as an alternative mitigation to risks that are mitigated by restrictive interlocking conditions in System B.
For trains supervised by System A to benefit from less restrictive interlocking conditions, without their drivers receiving contradictory information from the trackside equipment of System B, the information transmitted to them by System B must also be according to these less restrictive interlocking conditions. However, this introduces the risk that System B transmits information based on less restrictive interlocking conditions to a train that is not operating under System A.
In more detail, System B movement authorities are conveyed by the colour of aspects displayed on signals at fixed location, supplemented by signage indicating maximum permissible speeds. Minimal ATP functionality is provided.
System A is very flexible in terms of where movement authorities can be issued from and to. System B can only issue movement authorities from one signal to another. Furthermore, the ATP functionality of System A means that interlocking controls to control speed or mitigate the risk of a train travelling too far in System B are not required.
Fig. 2 illustrates that to benefit from this enhanced functionality, the aspects displayed in a System B signal 9 to drivers of trains supervised by System A ETCS on-board equipment, such as train 1A as shown, need to be consistent with ETCS movement authorities held by that ETCS on-board equipment. In Fig. 2, signal 9 provides a yellow "proceed" aspect consistent with ETCS movement authority (MA). However, this introduces the risk of a signal aspect authorizing the driver of a System B train to proceed as far as the next signal 10 in conditions where it would only be safe for a System A train to proceed. As shown, here in fact the presence of another train 1 1 on the approach to signal 10 would make it unsafe for a System B train to proceed past signal 9.
It is an aim of the present invention to mitigate these risks.
This aim is achieved, by the present invention, by using a failsafe method of applying different interlocking logic for authorizing trains supervised by System A to enter a route compared to the logic used for trains that are not supervised by System A. The logic applied for trains supervised by System A is less restrictive than that for other trains. The invention is failsafe because it ensures that this logic is never used to authorize a train not supervised by System A to enter a route. In failure scenarios, trains are either authorized to enter the route based on (more restrictive) logic appropriate to System B operation or not authorized to enter the route at all.
Having detected a first train entering the route, after having applied interlocking conditions for a train supervised by System A, the trackside signalling equipment will provide new authorization to enter the route in any of the following scenarios:
Trackside signalling equipment receives a report from the on-board signalling equipment supervising the first train, for which the interlocking conditions were selected, indicating that the first train has entered the route. In this case, the process of selecting interlocking conditions is repeated for the following train.
Trackside signalling equipment receives a report from the on-board signalling equipment, indicating that the first train is still on the approach to the route. This scenario can occur when the indication of a train entering a route resulted from a failure. In this case, trackside signalling equipment requires manual intervention by a signaller before providing a new authorization for a following train to enter the route. Following such signaller intervention, the process of selecting interlocking conditions is repeated for the following train (that has not yet entered the route).
Trackside signalling equipment receives no report from the on-board signalling equipment of the first train for more than a configurable period of time. This scenario can occur as a result of a communications failure between the onboard and trackside signalling equipment for example. In this case, the processes of identifying the next train to enter the route and of selecting interlocking conditions are repeated.
The trackside signalling equipment also ceases to authorize entry into the route if either of the following conditions occur without the trackside signalling equipment detecting a train entering the route:
Having selected interlocking conditions for a train supervised by System A, trackside signalling equipment receives a report from the on-board signalling equipment, that was supervising that train, indicating that it is no longer supervising the System A train for which the interlocking conditions were selected, and has not yet entered the route. In this scenario, trackside signalling equipment requires manual intervention by a signaller before authorizing entry for that train into the route. Following such signaller intervention, the process of selecting interlocking conditions is repeated for the train based on the new way in which the train is being supervised.
Having selected interlocking conditions for a train supervised by System A, trackside signalling equipment receives no report from the on-board signalling equipment for more than a configurable period of time. In this scenario, trackside signalling equipment requires manual intervention by a signaller before providing new authorization for that train to enter the route. Following such signaller intervention, the processes of identifying the next train to enter the route and of selecting interlocking conditions are repeated.
The present invention provides, for example:
A fail-safe means of identifying that the next train to enter a route is supervised by on-board signalling equipment in a specific way (referred to as System A herein);
The use of a method of detecting a train entering a route, that has a default 'failed' state of detecting a train entering a route, to stop authorization for a following train to enter the route, based on the interlocking condition for a train supervised by System A, being received by a following train that might not be supervised by System A;
The prohibition of authorization to enter a route after a train has been detected to enter that route after interlocking conditions for a train supervised in by System A have been applied;
The use of a configurable time from the last report received from a train that was supervised by System A, after which the train is no longer regarded as being supervised by System A;
Functionality to force manual intervention by the signaller in scenarios where there is ambiguity over whether the next train to enter a route is supervised by System A; and
Functionality in a device performing interlocking logic, that is separate from a device managing communications with trains, whereby any indication that the next train to enter a route is supervised by System A must be revoked after a train has been detected to enter the route before new authorization to enter the route is given.
In accordance with a first aspect of the present invention there is provided a method of applying interlocking logic for a train approaching a route, the interlocking logic being dependent on the signalling architecture used by that train, the signalling
architecture comprising one of a first architecture in which cab-signalling is used and a second signalling architecture reliant upon trackside signals, the method comprising the steps of:
a) determining if the train is at least potentially supervised by the first architecture,
b) determining if the train is the next train to enter the route, and
c) if in steps a) and b) the train is not so determined, then applying a first signal stick function to the route, or
d) if in steps a) and b) the train is so determined, then applying a modified signal stick function to the route.
In accordance with a second aspect of the invention there is provided an interlocking for a railway track configured to apply interlocking logic for a train, comprising means for effecting either a first or a modified signal stick function, the stick function being effected being dependent on the signalling architecture used by that train, the signalling architecture comprising one of a first architecture in which cab-signalling is used and a second signalling architecture reliant upon trackside signalling.
In accordance with a third aspect of the invention there is provided a railway system comprising the interlocking of the second aspect.
In accordance with a fourth aspect of the invention there is provided a railway system operable to effect the method of the first aspect.
Detailed description
The invention will now be described with reference to the accompanying figures, of which:
Fig. 1 schematically shows two signalling architectures;
Fig. 2 schematically shows a length of railway track;
Figs. 3a-f schematically show a first scenario in accordance with the present invention;
Figs. 4a-f schematically show a modification of the first scenario;
Figs. 5a-e schematically show a modification of the first scenario;
Figs. 6a-e schematically show a second scenario in accordance with the present invention;
Figs. 7a-f schematically show a modification of the second scenario;
Figs. 8a-f schematically show a third scenario in accordance with the present invention;
Figs. 9a-f schematically show a modification of the third scenario;
Figs. 10a-e schematically show a fourth scenario in accordance with the present invention;
Figs. 1 1 a-d schematically show a modification of the fourth scenario;
Figs. 12a-d schematically show an embodiment of the present invention;
Figs. 13a-d schematically show a further embodiment of the present invention;
Fig. 14 schematically shows a yet further embodiment of the present invention;
Fig. 15 schematically shows an additional embodiment of the present invention; and Fig. 16 schematically shows a further embodiment of the present invention.
Identifying trains supervised by System A
An initial step is to identify trains that are supervised by System A, i.e. those which are fitted with some form of wireless signalling system providing cab signalling, as opposed to those supervised by System B, i.e. a signalling system relying on trackside signals.
Trackside signalling equipment regards the next train to enter a route as being supervised in a specific way, i.e. by System A, for the purposes of applying less restrictive interlocking logic, when all of the following conditions are true: i) Trackside signalling equipment has identified a train that is approaching the route. This means that the train is on a path that leads to the route and is heading in the direction of the route entrance;
ii) Trackside signalling equipment has assurance that there are no other
vehicles between the identified train and the route entrance. This means that the train in question will be the next train to enter the route (provided that it continues to head in that direction);
iii) On-board signalling equipment has reported that the train is supervised by System A;
iv) The time since the last report from on-board signalling equipment, indicating that the train was supervised by System A, is less than a pre-configured value such that the report can still be deemed current; and
v) No train has been detected entering the route since the most recent report from on-board signalling equipment was received. This means that the train supervised by System A has not already entered the route.
Trackside signalling equipment authorizes this train to enter the route when the interlocking conditions, contained in the interlocking logic selected for a train supervised in the specific way, are satisfied.
If any condition is false, trackside signalling equipment regards the train as not supervised by System A for the purposes of applying less restrictive interlocking logic. In this case, (more restrictive) interlocking logic appropriate for a train signalled by System B is used. This applies even if the train is supervised by System A, but cannot be proven to be so.
In addition to determining whether a train is supervised by System A in the fail-safe manner above, trackside signalling equipment also determines whether a train is potentially supervised by System A. This is important when trains transition from being signalled by System B, and not supervised by System A, to being supervised by System A and vice versa. During this transition, the ETCS stick invention is applied as a precursor to applying less restrictive interlocking conditions.
Criteria i), ii), iv) and v) above are retained for regarding a train as potentially supervised by System A. However, criterion iii) above is replaced by the following: iii*) On-board signalling equipment has reported its status that the train is capable of receiving System A movement authority information that would cause it to be supervised by System A.
Signal stick conditions
The 'signal stick' (otherwise known as 'disengagement') function is a conventional signalling function (the name 'stick' here originating from relay signalling technology, in which a current path used to keep a relay energised via one its own contacts is known as a 'stick' path). The term "signal stick" itself is listed for example in the Glossary of Signalling Terms published by the Rail Safety and Standards Board, where it is defined as "The disengaging of a signal after it has been used by a train, to prevent the signal from subsequently showing a proceed aspect until the route has been cancelled and again set", while the term "disengagement" is also referred to in the British Railway Group Standards. The signal stick is a function that ensures that only one train is authorized to enter a route each time that a route is set (from a signal or other location). It is overridden if the route is working automatically, i.e. such that no action is required from a signaller or separate route-setting device to authorize a train to enter that route. System B trains are only authorized to enter the route when this conventional signal stick latch is set. The latch becomes set when a route is cancelled and is permanently set when a route is working automatically. It becomes unset when all of the following conditions are true:
A train is detected entering the route via train detection equipment that fails to the 'safe state' of detecting a train entering the route;
The train was authorized to enter the route at the time it did so; and
The route is not working automatically.
In accordance with the present invention, this conventional signal stick functionality is maintained for trains that are supervised by System B - including those that are not identified as being either supervised or potentially supervised by System A.
However, in accordance with the present invention, when trackside equipment determines that the next train to enter a route is potentially supervised by System A (by application of the criteria i), ii), iii*), iv) and v) set out above), it instead applies an "ETCS signal stick function", which is based on the conventional stick function. The application of ETCS signal stick functionality is a necessary condition for the application of less restrictive interlocking principles to trains supervised by System A.
[A further condition is that the train be regarded as 'supervised' rather than 'potentially supervised' by System A]. The state of the signal stick latch remains the same during this transition, but the following logic subsequently applies to it.
The signal stick latch becomes unset when a train is detected entering the route via the same failsafe train detection equipment used for conventional signal stick functionality. This occurs regardless of whether the train is actually authorized to enter the route and regardless of whether the route is working automatically.
When the signal stick latch is unset, no authorization is given to enter the route via System B, i.e. using a trackside signal. Authorization to enter the route may only be given via System A to the train that was identified as the next train to enter the route when ETCS stick functionality was applied. Furthermore, it can only be given if that train is still on the approach to the route entrance, i.e. if the signal stick latch had become unset due to a "right side" train detection failure (where "right side failure" means a failure of equipment that causes it to revert to a pre-defined safe state). In this way, ETCS stick functionality ensures that only one train is authorized to enter the route each time the signal stick latch is set. Therefore, if this authorization is based on less restrictive interlocking principles, the ETCS signal stick functionality ensures that these principles are only applied to a specific train, which is supervised by System A.
The signal stick latch becomes set again when any one of the following occurs:
A route is cancelled. This behaviour is as for conventional signal stick functionality;
A route is working automatically AND the train supervised by System A reports that it has entered that route. This behaviour differs from conventional signal stick functionality as the signal stick latch would never have been unset when a route is working automatically in conventional stick functionality; or
A route is working automatically AND the train supervised by System A fails to report to System A trackside equipment for more than a period of time. Again, this behaviour differs from conventional signal stick functionality in which the signal stick latch would never have been unset.
Having become set, the process of determining whether the next train to enter is potentially supervised by System A is repeated and the appropriate stick functionality applied.
In order to demonstrate the present invention more clearly, various scenarios will now be described in detail with reference to Figs. 3 to 1 1 . In these figures, a length of railway track is shown, with first and second signals 9 and 10 located along the track, similarly to as shown in Fig. 2, delimiting a route therebetween.
Scenario 1 : conventional signal stick functionality
Figs. 3, 4 and 5 illustrate a first scenario, wherein a leading train 1 LB signalled by System B approaches and enters the route. Here, signal stick functionality behaves in the conventional manner. In Fig. 3, the route is working automatically, hence the signal stick bit remains permanently set. Here a following train 1 FB is signalled by System B.
In more detail, in Fig. 3a, the leading train 1 LB, which is approaching the route, fails to meet the criteria for identification as under System A (i.e. it is likely to be signalled by System B), and the signal stick is set. Signal 9 provides a "proceed" (green) indication, as does signal 10.
In Fig. 3b, entry of train 1 LB into the route is detected by failsafe train detection means, such as a track circuit or the like. Signal 9 therefore is caused to provide a "stop" (red) indication.
In Fig. 3c, train 1 LB has fully entered the route, and the signal stick remains set.
In Fig. 3d, a following train 1 FB approaches the route.
In Fig. 3e, leading train 1 LB approaches the end of the route.
In Fig. 3f, leading train 1 LB exits the route. Signal 9 switches to provide a proceed indication, while signal 10 turns red, providing a stop indication.
In Fig. 4, the route is cancelled (see Fig. 4c) and set again (see Fig. 4d) between trains. It can be seen that otherwise, the situation is very similar as for Fig. 3.
In Fig. 5, the following train 1 FA is signalled by System A. Figs. 5a-c are identical to Figs. 3a-c, but in Fig. 5d the System A movement authority granted to train 1 FA is shown as extending up to signal 9. In Fig. 5d. since train 1 FA has positively confirmed that it is signalled by System A, the MA granted to it can now extend past the signal 9, i.e. so that less restrictive interlocking conditions are be applied. Signal 9 provides a proceed indication into the occupied route.
It can be seen that the behaviour of the signal stick latch is the same regardless of whether the following train is also signalled by System B, as in Fig. 3, or by System A as illustrated in Fig. 5. In the latter sub-scenario, the subsequent behaviour of the signal stick latch will be in accordance with the proposed ETCS stick functionality. Furthermore, if the following train positively confirms that it is supervised by System A, less restrictive interlocking conditions can be applied as represented by a proceed (yellow) aspect at signal 9 into an occupied route in Fig. 5.
Scenario 2: train confirms that it has entered route
Figs. 6 and 7 illustrate a second scenario, wherein ETCS stick functionality is applied when the next (i.e. leading) train 1 LA to enter a route is (or potentially could be) supervised by System A. The latch always becomes unset when a train is detected entering the route by failsafe train detection. This prevents new System A movement authorities being issued into the route, but does not affect any that have previously been issued. If the route is working automatically (or is cancelled), the latch becomes set again when the train confirms that it has entered the route as illustrated in Fig. 6. It should be noted that the latch also becomes set following route cancellation as for conventional signal stick functionality.
In more detail, in Fig. 6a, leading train 1 LA, approaching signal 9, confirms that it is signalled by System A, and the signal stick latch is set. The movement authority granted to the train extends past signal 10, with both signals 9 and 10 being green.
In Fig. 6b, the train 1 LA is detected entering the route by failsafe train detection means. This causes the latch to become unset. The train's MA is unaffected, but no new MAs may be issued which extend into the route.
In Fig. 6c, train 1 LA confirms that it has entered the route to the System A trackside equipment. This causes the latch to become set again.
In Fig. 6d, a following train 1 FA, which in this case is signalled by System A, approaches signal 9, and its MA extends up to that signal.
Fig. 6e shows that - similarly to Fig. 5 - as the following train is signalled by System A, its MA may extend into the route, i.e. past signal 9, even though leading train 1 LA is still located within that route.
ETCS stick functionality applies regardless of whether the following train is also signalled by System A, as in Fig. 6, or by System B as illustrated in Fig. 7. In the latter case, the subsequent behaviour of the signal stick latch will be in accordance with conventional signal stick functionality and potentially more restrictive interlocking conditions applied.
In more detail, since the leading train 1 LA is again signalled by System A, Figs. 7a-c are identical to Figs. 6a-c. In Fig. 7d, a System B signalled following train 1 FB approaches the route, and is identified as not being signalled by System A. The signal stick latch remains set.
Figs. 7e-f show that following train 1 FB may only enter the route once leading train 1 LA has exited the route, at which point signal 9 changes to provide a proceed indication, and signal 10 changes to red.
Scenario 3: train reports itself on approach to route
Figs. 8 and 9 illustrate a third scenario, wherein a System A-signalled leading train 1 LA is erroneously indicated as entering the route.
The train detection equipment used to unset the signal stick latch is designed to fail to the safe state of detecting a train entering the route. There is therefore a failure mode in which the signal stick latch becomes unset when no train has entered the route. When this occurs with ETCS stick functionality being employed, System B authorization to enter the route is withdrawn as it would be had a train actually entered the route. This ensures that no System B authorization, based on less restrictive interlocking conditions applicable to a System A train that may now have entered the route, is given to a following System B train.
Authorization via System A to a train that was on the approach to the route before the signal stick latch was unset will not be prevented by ETCS stick functionality, as this authorization is still applicable to the correct train. However, other System A / interlocking functionality may cause this authorization to be withdrawn as a failsafe response to the train detection failure.
In this scenario, the signaller must cancel the route to set the signal stick latch. The signaller must then set the route again to provide new authorization for a train to enter it. The process of determining whether the next train to enter the route is / is supervised by System A is then repeated as though for a new train approaching the route entrance. This is illustrated in Fig. 8 for the case where the train remains supervised by System A and in Fig. 9 where it reports that it is no longer supervised by System A.
In more detail, in Figs. 8a, 9a, the leading train 1 LA, identified as being signalled by System A, approaches the route. Its MA extends past signal 10, and the latch is set.
In Figs. 8b, 9b, the train 1 LA is erroneously detected as entering the route by the failsafe detection means, when in fact it is still approaching signal 9. The latch becomes unset.
In Figs. 8c, 9c, the signaller cancels the route.
Figs. 8d, 9d show the train's MA having been withdrawn. The latch is re-set due to the route cancellation.
In Fig. 8e, the train 1 LA is again determined to be signalled by System A, and reports itself as approaching the route. The signaller then sets the route again.
In Fig. 8f, an MA is granted to the train which extends past signal 10.
In contrast, in Fig. 9e, the train 1 LA reports that it is no longer signalled by System A. The signaller then sets the route again.
In Fig. 9f, a proceed indication is provided by signal 9, enabling the train to enter the route.
Scenario 4: train fails to report
Figs. 10 and 1 1 illustrate a fourth scenario, wherein communications equipment of System A on-board equipment fails. In this case, trackside signalling equipment will stop receiving reports from trains supervised by System A. It will therefore fail to receive confirmation that such a train has entered a route after train detection equipment indicates that this has occurred.
If trackside signalling equipment fails to receive a report for more than a pre- configured period of time from a train supervised by System A, it will regard that train as not supervised by System A. It should be noted that System A equipment onboard the train itself may also regard its authorization as invalid after a similar period of time. If the route is working automatically, the signal stick latch will be set again and the process of determining the state of the next train to enter the route is begun anew. Fig. 10 illustrates this for the case where the train has entered the route.
In more detail, in Fig. 10a, leading train 1 LA, approaching signal 9, is identified as being signalled by System A, and the signal stick latch is set. The movement authority granted to the train extends past signal 10, with both signals 9 and 10 being green.
In Fig. 10b, the train 1 LA is detected entering the route by failsafe train detection means. This causes the latch to become unset. The train's MA is unaffected, but no new MAs may be issued which extend into the route.
In Fig. 10c, the train has entered the route.
In Fig. 10d, the timer expires without train 1 LA, which has now left the route, reporting to the trackside equipment. A following train 1 FB approaches signal 9.
In Fig. 10e, the latch is reset due to the automatic working of the route.
The failure of communications from a train supervised by System A can occur at the same time as the signal stick latch is unset due to a right side failure of train detection equipment. In this case, the train remains on the approach to the route and, if the route is working automatically, the signal stick latch becomes set after expiry of the timer. This is illustrated in Fig. 1 1 .
In more detail, in Fig. 1 1 a, the leading train 1 LA, identified as being signalled by System A, approaches the route. Its MA extends past signal 10, and the latch is set.
In Fig. 1 1 b, the train 1 LA is erroneously detected as entering the route by the failsafe detection means, when in fact it is still approaching signal 9. The latch becomes unset.
In Fig. 1 1 c, the timer expires before the train has entered the route. In Fig. 1 1 d, the latch is reset due to expiry of the timer. Additional functionality
The present invention provides additional functionality for handling trains that were regarded as supervised by System A, but can no longer meet the criteria for being so.
This additional functionality is concerned specifically with routes that the train supervised by System A has not yet entered. The train ceases to be regarded as supervised by System A when:
it reports to trackside signalling equipment that it is no longer supervised by System A (This can occur in degraded mode operation and when the train changes its direction of travel);
no report is received from the train for a pre-configured period of time (as described with reference to the fourth scenario).
Where this additional functionality is implemented, the signal stick latch is unset when a train that has not entered a route from the signal ceases to be regarded as supervised by System A. To authorize the train to move again, the signaller must manually cancel the route and set it again (regardless of whether it is working automatically or not). This is illustrated in Fig. 12 for the case where the train reports that it is no longer supervised and in Fig. 13 for the case where no report is received from the train for a period of time.
In more detail, Fig. 12a the leading train 1 LA, identified as being signalled by System A, approaches the route. Its MA extends past signal 10, and the latch is set.
In Fig. 12b, train 1 LA reports that it is no longer supervised by System A. This causes the latch to unset. The signaller then cancels the route.
In Fig. 12c, the signaller resets the route.
In Fig. 12d, the latch is reset due to the route cancellation.
In Fig. 13a, the leading train 1 LA, identified as being signalled by System A, approaches the route. Its MA extends past signal 10, and the latch is set. However, the timer expires before the route is entered.
In Fig. 13b, the train is no longer identified as being supervised by System A due to the timer expiry, and the latch is unset. The signaller then cancels the route.
In Fig. 13c, the signaller sets the route again.
In Fig. 13d, the latch is reset due to the route being set.
Architecture specific features
The following are features of the invention specific to architecture in which interlocking equipment is implemented in a separate device to System A trackside equipment. These features are not applicable where the interlocking and System A trackside equipment are implemented in the same device:
Having detected a train entering the route, the device performing interlocking logic requires revocation of all indications from System A trackside equipment that the next train to enter the route is supervised by System A before new authorization to enter the route is given (via either system).
If the indication that the next train to enter the route is revoked, with no train detected entering the route, the device performing interlocking logic requires manual intervention by the signaller before new authorization to enter the route is given.
Possible further applications of the invention
Short block: -
Fig. 14 schematically illustrates a possible application whereby the methodology of the present invention can be used to improve railway capacity for trains supervised by System A on lines shared with trains signalled by System B by enabling the former to operate with shorter signalling block sections or with moving block sections. As shown, five trains are present on a section of track, with the three leftmost trains being supervised by System A and the fourth train being signalled by System B. The signalling system used by the fifth (rightmost) train is not of relevance for this discussion. It should be noted that in most normal operation scenarios, only one train is permitted to enter a block section at once, and consequently, shorter block sections enable trains to travel closer together. The
interlocking conditions to authorize a train supervised by System A to enter a route based on these shorter block sections are thus less restrictive than those for trains signalled purely with System B, and this is clearly shown in Fig. 14, where the system B train has a longer associated block. It can be seen that this is general case for the specific example of the first scenario discussed above.
Interlocking control override:-
Fig. 15 schematically shows how the methodology of the present invention can be used to improve railway capacity for trains supervised by System A on lines shared with trains signalled by System B by overriding restrictive interlocking controls that are not needed for System A. An example of such a control is the practice, known as approach control, of controlling speed by withholding authorization to enter a route until a train detection section has been occupied for a period. Approach control is not needed for System A as speed is indicated and supervised by other, less intrusive, means as is known in the art; it can therefore be overridden as illustrated. In more detail, Fig. 15 shows a three-stage time sequence for a train approaching a signalled junction 12 for each of the cases of a System A train 1 A and a System B train 1 B. In both cases, initially the signaller sets a route, and the correct exit from the junction is effected. However, while the System A train may be granted an MA which extends past the junction, the System B train has its proceed authorization withheld (i.e. the signal remains red) until an approach control timer determines that a set period has elapsed, at which point the signal provides a proceed indication.
Additional routes for trains supervised by System A:-
Fig. 16 schematically illustrates a feature made possible by the present invention whereby railway flexibility can be improved by enabling the provision of routes exclusively for trains supervised by System A. Here for example, two generally parallel railway lines 13, 14 are shown, the arrangement being such that for line 13, by virtue of their signalling, System B trains may only travel from left to right, but for line 14 System B trains may only travel from right to left. System A trains conversely can be signalled, and thus may travel, bi-directionally on each of these lines. As
shown in Fig. 16, this provides the possibility that a system A train 1A may be provided with an MA to enable travel from line 13 to line 14 and back to line 13, thus circumventing a track section of line 13.
Higher speeds through different approach locking conditions:-
The methodology of the present invention can be used to reduce railway journey times by enabling trains supervised by System A to operate at higher speeds.
System A enables trains to travel at higher speeds by providing them with longer movement authorities than is possible with System B. It should be noted that trains take a longer distance to stop from higher speeds, and therefore need longer movement authorities to travel safely at such speeds. However, in addition to this, the conditions appropriate for the releasing the route, known as 'approach locking conditions,' must be appropriate for the higher speed. There must never be a situation in which a route is released in front of a train, because the train was unable to stop before entering it.
The methodology of the present invention may cause approach locking conditions appropriate to the higher speed to be applied when a train potentially supervised by System A approaches the route. Unlike the examples discussed so far, these interlocking conditions are more restrictive than those for System B, hence they are applied even if the absence of positive confirmation that the train is actually supervised by System A. Application of these more restrictive approach locking conditions is then a pre-requisite to authorizing a train to enter a route via System A (and thereby at higher speed than via System B). These more restrictive approach locking conditions remain in force whilst there is a possibility that the train has or could receive a System A movement authority into the route.
The above-described embodiments are exemplary only, and other possibilities and alternatives within the scope of the invention will be apparent to those skilled in the art.