FIELD OF INVENTION The present invention relates to warning systems for trains approaching an area of risk. The invention also relates to a method operating such a warning system.

BACKGROUND OF INVENTION Train drivers always have to exercise caution and watch out for risks lying ahead on their tracks. Such risks e.g. might arise due to trackside engineering and repair work. But also severe weather conditions can cause the tracks to be covered with mud, soil or branches or cause the tracks or track bed to be damaged. Other obstructions on the tracks can result from people or animals. If not noticed in time by the train driver, the risks can lead to damage of the train or carriages, or even injuries to people. Also, for servicing personnel working on or alongside the tracks such incidences can pose a serious risk.

Because the typical speed of trains does not allow for sufficiently early visual detection of such risks by the train driver, a number of technical warning systems have been put into use or have been proposed.

Most of the warning systems which are positioned on a train serve to avoid the collision with other trains, especially oncoming trains on the same track. Patent US 5,574,469 for example relates to a method and system for improved collision avoidance of two locomotives by periodically receiving on each locomotive digitally encoded data to determine their geographical location, speed and direction of travel by means of an onboard global positioning system receiver. If a risk for collision is detected, avoidance procedures are automatically initiated, including the initiation of aural and visual alarms or the reduction of speed.

Patent US 7,317,987 concerns a collision warning and avoidance system which comprises an integrated on-board Train Navigation Unit and a GPS interface subsystem to locate a train. Further, a method is described which includes the step of receiving continuously from a network of satellites on a communication link one of a plurality of trains GPS ranging signals for accurately determining the position on a track. The method also requires communicating the status information to each other one of the plurality of trains and to a plurality of train control centres, and receiving at the one train each of the others' of the plurality of train status information. Other warning systems on a train use known locations of risk, such as crossings, to provide the train driver with a warning signal. Patent application US 2004/0015276 A1 e.g. describes a method and system for automatically activating a train warning device that uses a positioning system such as a global positioning system (GPS) receiver or an inertial navigation system (INS) to determine the train's position. The system further includes a database containing locations of crossings and other locations at which a train is required to give a warning signal and what regulations govern activation of the warning device at such locations.

By far the largest number of warning systems, however, concerns systems which send a warning signal to personnel who are not on the train but close to the tracks on which the train runs.

Patent US 5,554,982 e.g. describes a wireless train proximity alert system which provides a constant warning signal to warn vehicles approaching a train crossing when a train is also approaching the crossing. A transmission device, positioned on the train itself or at the side of the track, provides information on the train's speed and position. A crossing-based transceiver receives the train's proximity signal and transmits the boundary coordinates of a warning zone when the train's estimated time-to-arrival at the crossing is within a

predetermined range. A vehicle-based receiver receives the warning zone signal and the crossing's position, determines the vehicle's position and speed and produces an alarm to the vehicle' s operator when the vehicle is inside the warning zone and its distance to the crossing is within another predetermined range, which is a function of the vehicle's speed.

All these known systems have the disadvantage that they are designed for a specific risk situation and set up which hardly allows for a use in variable circumstances. In particular, the system is not able to adjust to different risk situations.

Therefore it is a desire to provide a warning system for trains which allows for the discrimination of different risk situations. In addition, it is desirable to provide an automatable system which is able to operate in such a variable risk environment. SUMMARY OF INVENTION

To address these problems, a warning system for trains is provided by present invention, which comprises:

- a mobile terminal which is operable manually and transmits upon operation a wireless message including the local coordinates of the mobile terminal and a risk parameter to indicate the type and/or severity of risk existing at the local coordinates;

a control centre which is adapted to receive the wireless message of the mobile terminal by means of a control centre receiver;

- a control centre processor comprised by the control centre adapted to process the risk parameter based on stored values of possible risk parameters and further adapted to identify all trains within a defined region around the local coordinates of the mobile terminal which are moving towards these local coordinates, and all trains within the defined region which are moving away from the local coordinates;

- a control centre transmitter comprised by the control centre which transmits at least a wireless alert signal for all those trains which have been identified to move towards the local coordinates of the mobile terminal, but not for the ones which move away from the local coordinates, if the risk parameter has been identified in processing to be critical. These problems are further addressed by a method for warning trains of a risk, comprising the following steps:

Operating a mobile terminal to transmit a wireless message including the local coordinates of the mobile terminal and a risk parameter to indicate the type and/or severity of risk existing at these local coordinates;

- Receiving a wireless message by a control centre receiver included by a control centre;

Processing the risk parameter with a control centre processor included by the control centre based on stored values of possible risk parameters;

Identifying all trains within a defined region around the local coordinates of the mobile terminal which are moving towards these local coordinates and all trains within the defined region which are moving away from the local coordinates;

Transmitting a wireless alert signal by a control centre transmitter included by the control centre for all those trains which have been identified to move towards the local coordinates of the mobile terminal, but not for the ones which move away from the local coordinates, if the risk parameter has been identified in processing to be critical. Typically, the local coordinates of the mobile terminal are obtained by a GPS, GLONASS or INS positioning system, however, may also be taken from a map or table.

The parameters which indicate the type and/or severity of risks are typically simple numbers, characters or strings of such numbers or characters. Certain incidents and/or risks may be linked to specific parameters, thus, allowing the control centre after processing these parameters to decide whether to send an alert message or not. For example, in case of loose branches on the tracks the parameter allows to identify the type of incidence

(branches on the tracks) and its risk level (low risk if the branches are small and can be removed easily).

While in this description the expression parameter it is used in its singular form, the skilled person understands that this expression also includes the meaning of its plural form, i.e. several parameters which are combined. For example, the parameter may consist of two sub-parameters of which one sub-parameter characterizes the type of risk, while the other sub-parameter characterizes the risk level.

According to this invention, the values of possible risk parameters which are stored at the control centre (i.e. can be retrieved there) are used to identify whether the transmitted risk parameter is critical or not. The risk parameter is critical if it is indicating that a risk resulting from or for the travelling trains might exist. Typically, this could be indicated if the risk parameter lies above a predetermined threshold.

The identification of all trains within the defined region around the local coordinates requires the knowledge of the train positions. These, typically, are known by an online GPS or GLONASS system which operates on the trains, allowing the control centre to have the information on the location of individual trains. When tracking the location of these trains over time, the control centre processor can also identify the speed of each train if this information is not already transmitted directly by wireless communication from the trains to the control centre. The control centre processor is also able to identify which trains move towards the identified coordinates and which ones move away from them e.g. when mapping the individual train information to a known track network in which the local coordinates of the mobile terminal is known. The region around the identified local coordinates may be defined in various ways. It could be defined as a simple circle or perimeter of any shape around the local coordinates in its centre, or it may be defined as a polygon connecting specific points on the train track network. Such points could be identified e.g. for individual trains or for different tracks differently.

When sending out the wireless alert signal, the discrimination between the trains which move towards the local coordinates and those which move away from them is typically achieved by an identifier for each individual trains or groups of trains. Does e.g. the control centre transmitter transmit an alert signal, it includes an identifier which is specific for each train or groups or trains. Therefore, the message is only transmitted for those trains, who match the identifier. Other trains possibly may receive the alert signal, but cannot read it or even receive it because of a lacking match with the identifier.

The inventive warning system relies on a mobile terminal which, e.g. can be carried by service personnel. Typically, the service personnel do not know about the type of risk before they reach the risk location. They might e.g. be called by members of the public or they are notified about a hazard whose risk level can only be judged at the location after inspection. The service personnel then will operate the mobile terminal which identifies the local coordinates. Further, the service personnel operates the mobile terminal and puts in risk related information, thus, allowing the risk parameter indicating the type and/or severity of the risk to be transmitted. The risk level might e.g. be considered low if the source of this risk can be removed easily or in a short period of time. It might also be considered low if the source does not cause any damage or danger in case of a collision with the train. Other risk levels can be adjusted.

Once the wireless message of the mobile terminal has been received by the control centre, the control centre processor is able to process the risk parameter and evaluate the risk level based on stored values (the storage does not have to take place at the control centre). If this evaluation has a negative result (i.e. a risk is existing), a wireless alert signal is sent out for all those trains which have been identified to move towards the local coordinates of the mobile terminal.

This alert signal may only be a simple signal warning the train driver of a general risk ahead, or it might provide the train driver with further information to allow him to take specific actions. E.g. the train driver might be informed of the risk parameter which was transmitted by the mobile terminal, thus providing the train driver with a relatively specific categorisation of the risk. To prevent confusion among train drivers whose train do not travel towards the risk location but e.g. away from it, it is envisaged to identify those trains within a defined region around the local coordinates which travel towards the risk location. All other trains, e.g. trains which are not moving or are travelling in a direction where no risk is expected would be

disregarded and shall be excluded from receiving or reading the alert signal.

An aspect of the present warning system is that the control centre transmitter is adapted to continuously transmit the at least one wireless alert signal for one of the identified trains moving towards the local coordinates until the control centre processor has established that the train has passed the location of the local coordinates. This reduces the risk for all trains within the defined region around the local coordinates. Alternatively, the control centre may also send an initial start alert signal, and a second finish alert signal, indicating that the train has already passed the risk zone. Continuous transmission here also includes an intermittent transmission, i.e. transmission which recurs at regular intervals.

In order to establish when a train might not be travelling towards the local coordinates (any more), it is required that the control centre is continuously informed about the location of the respective train. This, e.g. could be realized with a wireless GPS, GLONASS system which operates on the train to identify its location typically in real time. This location would then be sent on to the control centre to update the train location in their system. Once the control centre processor has established that no further risk exists for a respective train because it has already passed the local coordinates and moves away from them, the transmission of the signal is interrupted or stopped entirely for this train. This might also be realized by changing e.g. an identifier in the alert message which is transmitted by the control centre and received by the respective train.

A related idea might also be that the one of the identified trains is adapted to continuously emit a warning message to the train driver while it is receiving the wireless alert signal, which warning message in particular cannot be deactivated by the train driver. This allows to reduce the risk for the train within the defined region around the local coordinates. The warning message might be an aural or a visual message. Alternatively, the warning message might also be emitted upon receipt of an initial start alert signal, and it might be stopped upon receipt of a second finish alert signal, indicating that the train has already passed the risk zone. Continuous emission of a warning message also includes an intermittent emission, i.e.

emission which recurs in regular intervals. Such emission may be visual or acoustic in nature. To increase security in one particular embodiment, the warning message cannot be deactivated by the train driver and in particular is only deactivated once no further risk exists.

Another aspect of the present invention is that the control centre transmitter is adapted to transmit a wireless security message to the mobile terminal indicating whether any trains are present within the defined region moving towards the local coordinates; this will also increase the safety of the personnel operating the mobile terminal and prepare them for any risks which might result from the approaching trains.

The wireless security message might also contain information on whether any trains are present in the defined region at all and which ones move away from the local coordinates. Additionally, the wireless security message includes information on how many trains are present within the defined region moving towards the local coordinates and in particular when they are expected to arrive at the location of the local coordinates. This, again allows to increase the safety of the personnel operating the mobile terminal and prepare them for any risks which might result from the approaching trains.

In another aspect of the invention, the wireless alert signal includes information on how distant the location of the local coordinates is from the train receiving the wireless alert signal or how long it still will take the train to reach this location of the local coordinates; this, once more, allows to increase the security for the train driver and the train and prepare them for any risks which might lie ahead.

In another embodiment of the invention, the local coordinates of the mobile terminal are continuously updated and can change over time. Thus, in case that the service personnel operating the mobile terminal and the risk location does not remain stationary, the trains within the defined region can be notified of any change in risk location. If the local coordinates e.g. were initially relayed incorrectly or the risk level has been evaluated incorrectly, then the service personnel can override the initial wireless message, by retransmitting it with a new set of local coordinates or a change in the risk level. They may also opt to have the wireless alert signal cancelled if the incident has since been cleared. This again increases the security of all people and equipment involved. Alternatively, the local coordinates of the mobile terminal might also be lockable on the mobile terminal and do not change over time. This allows the service personnel to move around freely in and around the area of any stationary risks without confusing the travelling trains by changing the local coordinates. This, again increases the security.

In the event that there are poor mobile network conditions for the mobile terminal to initiate a wireless message, or the personnel is alerted of a remote incident at certain coordinates, this may require the mobile terminal to send coordinates that are different to its current location. Has the mobile terminal e.g. at a later time moved to a location where there is good network coverage, the user may then optionally relay remotely the local coordinates of the risk location instead. To support this feature, a mobile terminal software could utilise an option to save a current location, prior to moving the mobile terminal to the new location for sending the wireless message and provide information on the coordinates of the risk location.

In another aspect of the invention the defined region around the local coordinates of the mobile terminal is continuously updated. This might increase security in an environment in which the speed of trains or the direction of travel changes significantly. Further, the defined region around the local coordinates of the mobile terminal may be different for different trains and/or train tracks. This accounts for trains travelling at significantly different speeds or track conditions within the track network.

Alternatively, additionally to the defined region another second region is defined around the local coordinates and around the defined region. The second region allows for notifying trains travelling at much greater speeds towards the local coordinates of the risk location. Thus, trains which are present between the two defined regions travelling above a certain speed limit, which can be configurable, in the direction of the risk location could also be notified.

In another aspect of the invention, the control centre is adapted to operate automatically, and in particular is adapted to not need any human operator to process the risk parameter of the wireless message. This reduces the requirement of human work and reduces the risks for human error. Additionally, the automated system can operate much faster in comparison to a human operated system and react more quickly to any risks. In another embodiment of the invention, the control centre is adapted to send control messages at regular intervals to all trains within a control perimeter of possible track locations and the trains are adapted to send acknowledgement signals of these control messages back to the control centre. Typical intervals are e.g. hourly. Train drivers and control centre staff might be be unaware of the transmission of these messages and signals, however in the event of failure to receive one or a small number of acknowledgement signals by the control centre within a period of time, then control centre staff can be alerted that there is a possible loss of communications with a train, highlighting a possible hardware or software fault. If Communication Based Train Control (CBTC) systems are used, then this may already flag up communications outages and therefore assist in addressing this issue. This increases the security of all people and equipment involved.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned attributes, features and advantages of this invention and the manner of attaining them will become more apparent and the invention itself will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein

FIG. 1 shows a schematic drawing according to a first embodiment of the invention, in which the defined region around the risk location is simply defined by a circular perimeter with the risk location in the center,

FIG. 2 shows a schematic drawing according to a second embodiment of the invention, in which the defined region around the risk location is defined by a non- circular perimeter,

FIG. 3 shows a schematic flow diagram representing an embodiment of the inventive method for warning trains of a risk.

DETAILED DESCRIPTION OF INVENTION

Figure 1 shows a first embodiment of the invention in schematic depiction. A warning system 1 comprises different parts. A mobile terminal 10 which is operated manually typically by servicing personnel is located at the place at which a risk incidence might arise if trains 101 , 102, 103 would travel to it without extra caution. E.g. servicing personnel would go to such location with the mobile terminal 10 after they were notified of a hazardous situation. This situation could arise due to broken trees, a ravine, people walking on the tracks or any other situation, which requires the servicing personnel to inspect said location.

Once set up, the mobile terminal 10 is operated by the service personnel and can transmit a wireless message 1 1 including the local coordinates 12 of the mobile terminal 10 indicating the risk location. The wireless message 1 1 also includes a risk parameter which indicates the type and/or severity of the risk existing at the local coordinates 12. The servicing personnel might have to select a suitable risk parameter on the mobile terminal 10 or chooses from a table of possible risk situations which are e.g. displayed on the mobile terminal 10. Their choice would then be translated by the mobile terminal 10 into a suitable risk parameter and will be included in the wireless message 1 1.

This wireless message 1 1 is subsequently received at a remote control centre 20 which is adapted to receive the wireless message 1 1 with a control centre receiver 21 . This control centre receiver 21 then delivers this information to a control centre processor 22 comprised by the control centre 20 and adapted to process the risk parameter based on stored values of possible risk parameters. The storage of these risk parameters does not have to take place at the control centre 20 itself, but the information has to be retrievable by the control centre processor 22 and is used in the risk evaluation. Typically, the evaluation is done by comparison of the stored and transmitted parameters. If this comparison results in a negative outcome (a risk is existing), then only those trains 101 , 102, 103 shall be notified of the risk situation which happened to travel towards the location of risk, i.e. the local coordinates 12. For this distinction of travel direction, the control centre processor 22 is further adapted to identify all trains 101 , 102, 103 within a defined region 30 around the local coordinates 12 of the mobile terminal 10 which are moving towards these local coordinates 12. This predefined region 30 is depicted as a simple circle with the local coordinates 12 of the mobile terminal 10 at the centre of this circle. The radius of this circle is selected to minimize the risk for all people involved and all trains and other equipment. For this selection, the speed of the trains 101 , 102, 103, the condition and type of the tracks 201 , 202, 203, the weather and many other items can be taken into account.

Further, taking into account the current position of all trains 101 , 102, 103 in this defined region 30, the control centre processor 22 establishes which trains 101 , 102, 103 move towards the location of risk and which ones move away from it. The trains 101 , 102, 103 which do not move at all can be disregarded in this example, although the skilled person might also consider them if required. Normally, the control centre processor 22 will have access to all the current train position data which is e.g. transmitted from the trains 101 , 102, 103 to the control centre 20 by means of a GPS based system. Because only those trains 101 , 102, 103 which are moving towards the location of risk need to be informed about the risk lying ahead, a control centre transmitter 23 comprised by the control centre 20 transmits at least a wireless alert signal 24 for all those trains which have been identified to move towards the local coordinates 12 of the mobile terminal 10. In contrast, all trains 101 , 102, 103, which are moving away from the local coordinates 12, however, would not receive the alert signal 24, since no further risk exists for them or results from them.

The wireless alert signal 24 is only transmitted by the control centre transmitter 23 if in the processing of the risk parameter by the control centre processor 22 it has been established that a critical risk exists. This may be established as explained already above.

According to the depicted situation, three trains 101 , 102, 103 are located on three different track sections 201 , 202, 203 of the network. Train 101 is located on track section 201 and moves away from the local coordinates 12 of the risk location. Train 102 is located on track section 202 and moves towards the local coordinates 12 of the risk location. Train 103 is located on track section 203 and also moves towards from the local coordinates 12 of the risk location.

While the defined region 30 has been selected to cover the region in which trains 101 and 102 operate, it does not cover the region in which train 203 operates. Because train 101 will not encounter a risk situation at the location of risk (assuming it does not change its direction) it also will not receive the alert signal 24 which is transmitted by the control centre transmitter 23. Also, train 103 does not receive this alert signal 24 because it operates outside of the defined region 30.

While the track section 203 is straight and allows train 103 to travel significantly faster than e.g. train 102 on track section 202, which is curved or has significant slopes or is in poorer condition, train 103 might still reach the location of risk before train 102. Hence, train 103 also needs to be notified of the risk at the local coordinates 12 in order to avoid any danger to people or equipment. The embodiment of Figure 2 solves this problem simply by changing the shape of the perimeter of defined region 30. While the defined region 30 stretches out from the local coordinates 12 further on track sections 201 and 203 (the faster track sections), it stretches out less towards the curvy track section 202.

The effect of the redefinition of this defined region 30 is that now all the trains 102 and 103 moving towards the location of risk are covered by the defined region 30 and the alert signal 24 will be received by both of these trains 102 and 103. It should be pointed out that according to the presented depictions, only an alert signal 24 is transmitted to the two trains 102 and 103 but not to train 101. In the real world, however, the alert signal 24 will reach all trains 101 , 102, 103, while only the two trains 102, 103 will be able to read or receive this alert signal 24. Technically, such discrimination might be realized with an identifier for each individual train 102 and 103 which is attached to the alert signal 24.

Furthermore, in both depicted embodiments it is possible for the control centre transmitter 23 to transmit a wireless security message 25 to the mobile terminal 10 for example indicating whether any trains 101 , 102, 103 are present within the defined region 30 moving towards the local coordinates 12. The wireless security message 25 might also include information on how many trains 101 , 102, 103 are present within the defined region 30 moving towards the local coordinates 12 and in particular when they are expected to arrive at the location of the local coordinates 12.

Figure 3 shows a schematic flow diagram representing an embodiment of the inventive method for warning trains 101 , 102, 103 of a risk. The method includes the following steps:

Operating a mobile terminal 10 to transmit a wireless message 1 1 including the local coordinates 12 of the mobile terminal 10 and a risk parameter to indicated the type and/or severity of risk existing at these local coordinates 12; (method step 301 )

Receiving a wireless message 1 1 by a control centre receiver 21 included by a control centre 20; (method step 302)

Processing the risk parameter with a control centre processor 22 included by the control centre 20 based on stored values of possible risk parameters; (method step 303)

Identifying all trains 101 , 102, 103 within a defined region 30 around the local coordinates 12 of the mobile terminal 10 which are moving towards these local coordinates 12 and all trains 101 , 102, 103 within the defined region 30 which are moving away from the local coordinates 12; (method step 304)

Transmitting a wireless alert signal 24 by a control centre transmitter 23 included by the control centre 20 for all those trains which have been identified to move towards the local coordinates 12 of the mobile terminal 10, but not for the ones which move away from the local coordinates 12, if the risk parameter has been identified in processing to be critical, (method step 305)