Title:
'Device For Improving Safety Of TPWS/ETCS In Absolute Block Working "
Complete Description:
This Invention relates to improvement of Safety of Trains fitted with balise or transponder based Train Protection Warning Systems (TPWS), like the European Train Control System (ETCS), which is now widely being used by Railways all over the world.
ETCS/TPWS prevents accidents between two trains on the same track and works in conjunction with the line side signals. It enforces speed restrictions to match the aspects of the Signal. If a signal is red, and the driver ignores the Red Signal, the ETCS/TPWS will automatically apply brakes, to stop the train. This system works well in Automatic Signaling Sections and within the Station Section.
However, a problem arises when the ETCS/TPWS is used in Absolute Block System. In this system only one train is permitted on a line between two stations. The entry into the block section is controlled by two signals on either end, in case of single line section and by a Home Signal at the entry side of a double line section. These signals are controlled by Block Instruments or Axle Counter Block Proving Devices.
The ETCS/TPWS system docs not folly cover the safety of train operation in the Absolute Block system between two stations and becomes ineffective under the following circumstances:

• There is a failure of the station interlocking system and hence failure of Signals authorizing Trains to Pass
• Block Instrument failure.
• Faults or temporary shut down of one line of a Double Line system, thereby forcing the remaining line to be used for train movement in both directions.
In all these cases, trains are permitted to move in and out of the block section by issuance of a Paper Line Clearance Ticket issued by the Station authority. It is quite possible that conflicting movement authority may be issued, jeopardizing safety. A similar safety hazard can arise when a train enters into a wrong line in a double line section.
The said invention creates two Safety Zones at either end of the Block Section. These Safety Zones are located immediately after the Last Stop Signal of the Originating Station and just before the Home Signal of the Destination Station. This zone has a geographical length of about 3 kilometers. These two safety zones are provided with commercially available Transponders, which can be one of Balises or RFID Tags, mounted on the track, at appropriate locations. For convenience sake, we will refer to these Transponders using the term "Balise". These Balises are in turn connected to Line side Electronic Units, which can write information on the Balises that they arc connected to. The information in the Balises is read by the TPWS/ETCS equipment on the Train. The Safety Zone also has a Train Direction Sensing Device. The LEUs and the Train Direction Sensing Device are in turn connected to pair of Command and Control Units (CCU),

which can communicate with each other. The CCUs also receive inputs from the Axle Counter Block Proving Device if they are provided in that section.
Once a train enters into a Safety Zone at one end of the Block Section, The CCU of that Zone communicates with its pair CCU at the Safety Zone at the Destination Station. Any other train equipped with TPWS/ETCS trying to enter into cither of these Safety Zones is automatically stopped by the onboard TPWS/ETCS braking mechanism. Both the Safety Zones are normalized only when the first train reaches the Destination Station.
This device/system is used as an add-on facility to the TPWS/ETCs systems. While TPWS/ETCS provide protection at the signals within the Station Sections, this device provides protection in the Absolute Block section even when the protecting Signals / Block fails during temporary single line working, or when a driver enters into wrong line in double line section A modification in the TPWS/ETCS the software will be required to handle Paper Line Clearance working. In the Paper Line Clearance mode of working, the TPWS/ETCS will ignore all the Balises in that section excepting the Balises in the Safety Zones in that section.
In Block Sections equipped with Axle Counter Block Proving Device, the said Invention, utilizes inputs from the Axle Counter Block Proving Device to add an additional layer of safety in case the Axle Counter Block Proving Device fails.

The Invention comprises of a pair of Safety Zones, Train Direction Proving Device, Balisc (Transponders) for Track to Train communication. Communication link between the Safety Zones, Track side Electronics in the form of Line Electronic Units (LEU) to write the information to the Balise, a pair Control and Command Unit (CCU), interconnected by Communication Media. The Command and Control Unit consists of Electronic Circuits programmed with appropriate Logic and Communication Modules for receiving information from its pair CCU, Train Direction Sensing Devices, Axle Counter Block Proving Devices and Line Electronic Units, The CCU passes commands to the LEUs to dynmically write on the Balises they are connected to. A Red Aspect written on the Balisc is read by a Train passing over it. The TPWS/ETCS will automatically apply the brakes andstop the train if it passes over a Balise showing Red Aspect.
The Train Direction sensing device that that can be based on any one of tfie existing known methods. Track Circuit based. Axle Counter based or RFID based. The Train Direction sensing device, covers the Safety Zone and can sense the Direction of the train anywhere in the Safety Zone.
Once a train enters into a Safety Zone at one end of the Block Section, the train entering information is sensed by the CCU at the Originating Station. If the block section has an Axle Counter Block Proving Device this input is also fed to this CCU. This information is conveyed by to the CCU of Safety Zone at the other end of the Block Section, through Communication Media which can be any one of cable, OFC or wireless media. The CCU at the Safety Zone at the Destination Station communicates with the LEU and conveys a Red Indication to the Balise.

1
If any train equipped with TPWS/ETCS enters into this block and passes over this Balise, it is automatically stopped by the onboard TPWS/ETCS braking mechanism. The Balises in the safety zone at the originating station are also brought to Red, so that another train cannot follow the first train when the first train is still in the Block Section. Both the Safety Zones are normalized only when the first train reaches the Destination Station.
Figure 1, is an embodiment of the Invention in a Single Line Section. Station A (1) and Station B (2) are connected by a Single Line (17) representing the Block Section. Signal (15) and Signal (16) control the movement of trains leaving Station A and Station B, respectively. Safety Zone (3) and Safety Zone (4) located as shown in the figure. Balises (5) and (6) are connected to LEU (9) of Safety Zone of Station A and Balises (7) and (8) are connected to LEU(IO) of Safety Zone of Station B. These LEUs are in turn connected to Command and Control Units (11) and (12). Directions Sensing Devices (13) and (14) are connected to CCUs (11) and (12) respectively. Inputs (20) and (21) fi"om Axle Counter Block Proving Devices are also fed into CCUs (11) and (12) respectively. The CCUs communicate with each other through Communication Media (18).
Initially, both the Safety Zones (3) and (4) are in normalized condition. Consider a Train (19) fitted with TPWS/ETCS moving from Station A to Station B. As soon as the Train enters the Safety Zone (3), its direction is sensed by Train Direction sensing Device (13) and communicated to CCU (11). CCU(11) communicates the information of a train occupying Safety Zone(3) of Station A and traveling towards Station B, to the CCU(12) of Safety Zone (4) of Station B. The CCU (11) of Station A, monitors the movement of this Train (19) and the

moment it crosses Safety Zone (3) towards Station B, it send a command to LEU (9). LEU(9) writes Red Aspect on Balises (5) and (6). The CCU(12) of Station B receives the information from CCI(11) and sends a command to LEU(IO), which writes Red Signal Aspect information on Balises (7) and (8). Train (19) is now between the two Safety Zones and the Balises in both the Safety Zones are now showing Red Aspect.
Consider an event now where another train starts from Station B to Station A, when Train (19) is on its way from Station A to Station B. When the train leaving Station B enters the Safety Zone (4) of Station B, it move over the first Baise (8), which transfers the Red Aspect information to the Balise Reader of the onboard TPWS/ETCS on the Train. The moment the Red Aspect on the Balise is sensed by the onboard TPWS/ETCS equipment, the train is automatically stopped. The driver now knows that there is a train coming towards him in the Block ahead and takes corrective action to make way for the entry of Train (19) into Station B.
Considering Station A, the Red Aspect on Balises (5) and (6) ensure that no other train can leave Station A towards Station B. Any train trying to enter the Block will automatically be stopped by Safety Zone (3). The Block Section (17) is now effectively locked and no train can enter this block from either end.
When Train (19) approaches Station B, it will enter the Safety Zonc(4) of station B. the Direction Sensing Device (14) senses the direction of this Train (19) as being from Station A to Station B and conveys the information to CCU(12).

CCU(12) sends a command to LEU (10) to remove the Red Aspect on Baliscs (7) and (8), so that the Train can enter station B.
Once the Train(19) leaves Safety Zone(4) towards Station B, CCU(12) communicates this information to CCU(11) of Station A. CCU (11) removes the Red Aspect on Balsises (5) and (6) through LEU (9). Both the Safety Zones are now normalized.
A similar sequence of operations will start when a Train leaves Station B towards Station A. Safety Zone (4) of Station B will now initiate the Locking of the Block.
In the case of a section provided with Axle Counter Block Proving Device, the Inputs from these will provide an additional level of redundancy and hence reliability, to the Safety Zones. In case the Axle Counter Block Proving Device system fails, the said invention still maintains safe movemnt of trains in the block section.
In a single line section, Balises and Signals will be available on the same track for trains running in both directions. A Train will need to work on Paper Line Clearance, only when there is a Block failure. In this case, the onboard TPWS/ETCS will be switched to Paper Line Clearance Mode. The Safety Zones in the said Invention will ensure full protection for the train in that section.

Figure 2, is an embodiment of the Invention in a Double Line Section. Station A (52) and Station B (53) arc connected by Double Lines (26) and (27) representing the Block Section. Signal (46) and Signal (47) control the movement of trains leaving Station A and Station B, respectively.
Station A Safety Zones (22) and (23) are as shown in the figure. Balises (28) and (29) are connected to LEU (34) of Safety Zone (22) and Balises (31) and (32) are connected to LEU (35) of Safety Zone (23). LEUs (34) and (35) are connected to CCU (36). Direction Sensing Devices (30) and (33) are connected to CCU (36).
Station B Safety Zones (24) and (25) are as shown in the figure. Balises (44) and (45) are connected to LEU (39) of Safety Zone (24) and Balises (41) ami (42) are connected to LEU (38) of Safety Zone (25). LEUs (38) and (39) are connected to CCU (37). Direction Sensing Devices (40) and (43) are connected to CCU (37). Inputs (50) and (51) fi"om Axle Counter Block Proving Devices are also fed into CCUs (36) and (37) respectively. The CCUs communicate with each other through Communication Media(50). The CCUs arc designed to take inputs for more than 2 lines and treat the fimctioning of each line separately.
Initially, all the Safety Zones arc in normalized condition. In the normal case, a Train(48) moving fix>m Station A to Station B, will move on line (26) and Train (49) moving fi-om Station B to Station A, will move on line (27). The protection for each of these lines using the said invention will be as detailed for a single line section, with the Safety Zones (22) and (24) locking the Block on line (26) and

the Safety Zones (23) and (25) locking the Block on line (27) respectively, to provide safety.
In the case of Temporary Single Line working due to failure in one line of the Double line section, a Train is allowed on the working line with Paper Line Authority. In the case of Line (27) failing. Train (49) going from Station B to Station A, will be given Paper Authority to travel on line (26). The onboard TPWS/ETCS will be switched to Paper Line Clearance Mode so that it will disregard the normal Signal Balises, but will be programmed to read the Baliscs of the Safety Zones on line (26). Train (49) then proceeds to enter Safety Zone (24). If the Block Section on line(26) is unoccupied and the Safety Zones arc in normalized condition, it will be permitted entry. After entry into this Safety Zone (24), the Safety Zone Balises (28) and (29) will have Red Aspect to prevent any other train entering the block, until the train(49) reaches and crosses Safety Zone (22) at station A. The Balises (44 and 45) in Safety Zone (24) will also show Red Aspect until the train crosses Safety Zone(22). Once the train crosses the Safety Zone (22), both the Safety Zones are automatically normalized.
In the case of a section provided with Axle Counter Block Proving Device, the Inputs from these will provide an additional level of redundancy and hence reliability, to the Safety Zones. In case the Axle Counter Block Proving Device system fails, the said invention still maintains safe movement of trains in the block section.

The Invention thus assures safety in Absolute Block Sections, no matter how trains enter the block section - with authority of a signal or paper authority, or without authority due to accidental entry or willful disobedience to rules. The Invention is independent of the working of the Station Interlocking System or the Block Instruments, or Axle Counter Block Proving Device between Stations

We claim
1. A Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working, by creating a pair of Safety Zones at each end of a Block Section, the said Safety Zone Comprising of Balises, Train Direction Sensing Devices, Axle Counter Block Proving Device, Line Electronic Units, a pair of Command and Control Units with appropriate logic, interconnected and interacting with each other, to perform the task of improving safety in trains, running in Absolute Block Sections, by automatically stopping and denying entry to any other trains into the Safety Zones, if a train is already in that Block within the Safety Zones.
2. A Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working, claimed in Claim (1), wherein a pair of Safety Zones are created, one on each side of a Block Section, with the purpose of automatically stopping any train trying to enter into cither of these Safety Zones, when a train is already in the block section between these Safety Zones.
3. A Device for improving Safety of Trains equipped with TPWS/ETCS, in
Absolute Block Working, claimed in Claim (1), wherein these Safety Zones
contain Balises, Line Electronic Units and Train Direction Sensing Devices
connected to a Command and Control Unit.

4. A Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working, claimed in Claim (I), wherein the Command and Control Unit consisting of Electronic Circuits programmed with appropriate Logic and Communication Modules, in conjunction with information from its pair CCU, Train Direction Sensing Devices and Line Electronic Units, ensures that the Balises in the Safety Zones transmit Red Aspect to any train trying to enter the Safety Zone at either end, when there is a train already present in the Block Section.
5. A Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working, claimed in Claim (1), wherein the Command and Control Unit is capable of receiving Inputs from Block Proving Axle Counter ^ Systems as an additional level of input for providing safety and reliability and can provide safety of train movement even in the event of failure of the Block Proving Axle Counter System.
6. A Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working, claimed in Claim (1), maintains the principle of absolute block system of working, which states that there should be only one train in the block at any time, is fully enforced, no matter how trains enter the block section - with authority of a signal or with paper authority, or without authority due to accidental entry or willful disobedience to rules.

7. The "Device for improving Safety of Trains equipped with TPWS/ETCS, in Absolute Block Working" according to any of the Claims from 1 to 7, substantially as herein described with reference to and as shown in Figures 1 and 2 of the accompanying drawings.