Method and system for controlling a vehicle

Abstract

 Traffic detection system (4) for detecting a motion of a vehicle (2) on a track (1), the traffic detection system (4) including a traffic sign state detection arranged for detecting at least a stop state signal (S3) of a traffic sign (3), the stop state signal indicating to the vehicle to stop at or before a standstill position (x0) at the traffic sign (3), wherein the traffic detection system (4) includes a motion detector (5), the motion detector (5) being arranged for measuring at least one of a set of motion parameters of the vehicle, and the traffic detection system (4) is arranged for determining based on the at least one motion parameter obtained by the motion detector (5), a prediction signal relating to the vehicle (2) while approaching the traffic sign (3), to predict if during the stop state signal (S3) the vehicle (2) is capable to stop at or before the standstill position (x0).

Description

Field of the invention

[0001] The present invention relates to a method for detecting undesired motion of a vehicle as defined in the preamble of claim 1. Also, the present invention relates to a system for detecting undesired motion of a vehicle.

Prior art

[0002] Such a method and system are known as traffic detection method and traffic detection system. Traffic detection systems are capable of detecting motion of a vehicle that ignores a stop signal of a traffic sign.

[0003] In railway systems, a traffic detection system is known, which can take over control of a train when the train passes a traffic sign that indicates a stop signal. Ignoring the stop signal occasionally happens when an engine driver mistakenly overlooks the signal.
Clearly, in that case a traffic accident may result with potentially serious consequences for personnel, passengers and equipment.

[0004] Therefore, the traffic detection system may automatically force the train to stop. In the prior art, some traffic detection system are known which function only at speeds above a predetermined velocity. Traffic detection systems according to this type are applied in for example, the railway system of the Netherlands, where a velocity of 40 km/h is the threshold value. In most cases where the velocity of the train is above this safety threshold, which determines whether to intervene or not, the traffic detection system from the prior art suffices to prevent an accident. A traffic detection system using this safety threshold is known as an automatic train protection system.

[0005] However, below this predetermined velocity the traffic detection system remains idle. The train passing the traffic sign when a stop signal is active, may be detected, but no action is initiated by the traffic detection system.

[0006] Thus, under circumstances where trains move at or below the predetermined velocity, for example, when approaching or leaving a railway station, or on some particular parts of the railway track, no external control over the train by the traffic detection system is possible. At such locations with velocities below the safety threshold, no intervention by the traffic detection system will happen.

[0007] Especially in these "low velocity" areas, where the situation may be more complex for an engine driver to overlook, the risk of ignoring traffic signs is relatively higher.
Moreover, even at relatively low velocity, accidents may still be serious.

[0008] From the prior art, a traffic detection system that can intervene at each velocity is known from a European standard ERTMS. However, the proposed system is not yet fully implemented due to, mainly, costs and complexity.

[0009] It is an object of the present invention, to provide a system and method for detecting undesired motion of a vehicle which reduce the risk of a driver overlooking a traffic sign and thus the risk of accidents involving that vehicle. Additionally, it is an object of the present invention to provide an additional measure for the prevention of accidents at low velocity.

[0010] The present invention relates to a traffic detection system as defined in the preamble of claim 1, characterised in that the traffic detection system further comprises a motion detector, the motion detector being arranged for measuring at least one of a set of motion parameters of said vehicle, and the traffic detection system is arranged for determining based on said at least one of a set of motion parameters obtained by the motion detector, a prediction signal relating to the vehicle while approaching the traffic sign, to predict if during the stop state signal the vehicle is capable to stop substantially at or before the standstill position.

[0011] The present invention provides a way to determine if a vehicle is going to pass the traffic sign without stopping. Advantageously, the present invention detects this error before the actual passing of the traffic sign occurs.

[0012] The determination is preferably based on determining a path to be traversed based on at least one of measured motion parameters of the vehicle, such as velocity, deceleration, and their relative change and on the distance of the vehicle from the traffic sign. During the determination procedure braking characteristics of the vehicle may be provided, and based on these braking characteristics the determination procedure may provide a prediction if the vehicle will be able to stop before the traffic sign.

[0013] If the prediction indicates the vehicle cannot stop within reasonable certainty, the present invention will provide an interaction with the driver.

[0014] In a further aspect, the present invention is capable of providing an alert signal for directing the attention of the engine driver towards the stop signal of the traffic sign.. Due to the alert signal, the engine driver may possibly correct his error before passing the sign, may be able to act on the stop signal of the traffic sign, and may prevent a possible accident.

[0015] Such an alert signal may be an optical signal, for example a strobe signal at a high intensity or an audible signal.

[0016] Advantageously, the application of a special alert signal may assist in preventing accidents that occurring at velocities below the safety threshold, where no active control by the traffic detection system is possible.

[0017] In a further aspect of the present invention, other types of alert signal may be used and involve a communication signal to a mobile receiving unit in the engine cabin.

[0018] In a still further aspect of the invention, such a communication signal may be used to provide an action to initiate braking to stop the vehicle.

[0019] Further, the present invention relates to a method for traffic detection as described above, characterised in that the method comprises the step of:

• determining, based on measurement of at least one of a set of motion parameters, a prediction signal relating to the vehicle while approaching the traffic sign, to predict if during the stop state signal the vehicle is capable to stop substantially at or before the standstill position.

[0020] Moreover, the present invention relates to a computer system for use in traffic detection system for detecting a motion of a vehicle on a track, the traffic detection system comprising a traffic sign state detection, the traffic sign state detection being arranged for detecting at least a stop state signal of a traffic sign, the stop state signal indicating to the vehicle to stop at or before a standstill position at the traffic sign, the computer system comprising processing means and memory;
characterised in that
the traffic detection system further comprises a motion detector, the motion detector being arranged for measuring at least one of a set of motion parameters of the vehicle, the processing means are connected to the memory, to the traffic sign for receiving the stop state signal and to the motion detector for receiving the at least one of a set of motion parameters of the vehicle,
and the computer system is arranged to enable the traffic detection system to perform:

based on at least one of a set of motion parameters, determining a prediction signal relating to the vehicle while approaching the traffic sign, to predict if during the stop state signal the vehicle is capable to stop substantially at or before the standstill position.

[0021] Additionally, the present invention relates to a computer program product to be loaded by a computer system for use in a traffic detection system as described above,
characterised in that the computer program product after being loaded allows the processing means to carry out:

based on the at least one of a set of motion parameters, determining a prediction signal relating to the vehicle while approaching the traffic sign, to predict if during the stop state signal the vehicle is capable to stop substantially at or before the standstill position.

[0022] In a preferred embodiment the system has a compact form which can be installed on a traffic sign.

[0023] Preferred embodiments and other advantageous developments can be derived from the dependent claims.

Brief description of drawings

[0024] The invention will be explained in more detail below with reference to a few drawings in which illustrative embodiments thereof are shown. They are intended exclusively for illustrative purposes and not to restrict the inventive concept, which is defined by the claims.

Figure 1 shows diagrammatically a vehicle in approach of a traffic sign;

Figure 2 shows schematically a detection system for detecting undesired motion of a vehicle;

Figure 3 shows a flow diagram of a procedure for the detection system to carry out a method in accordance with the present invention;

Figure 4 shows a diagram of vehicle speed vs distance to traffic sign in accordance with the present invention.

Description of preferred embodiments

[0025] For the purpose of teaching of the invention, preferred embodiments of the method and devices of the invention are described below. It will be appreciated by the person skilled in the art that other alternative and equivalent embodiments of the invention can be conceived and reduced to practice without departing form the true spirit of the invention, the scope of the invention being limited only by the appended claims.

[0026] Figure 1 shows diagrammatically a vehicle in approach of a traffic sign.

[0027] The present invention relates to a situation as depicted in Figure 1: On a track 1 a vehicle 2 approaches a traffic sign 3. The track in this case is a railway track, and the vehicle 2 is a train. The train 2 travels towards the traffic sign 3 at a given speed ν and a given acceleration α, as indicated by the arrow. The distance between train 2 and a standstill position x0 at the traffic sign 3 is denoted by the double arrow x.

[0028] At the standstill position x0 of the track 1, the train must be at a standstill. Beyond that point x0, the train 1 is considered to have passed the traffic sign 3. It is noted that depending on the actual situation the standstill position x0 may be before the traffic sign (as seen from the train) or behind the traffic sign 3.

[0029] The traffic sign 3 is capable of displaying a signal S to the driver of the train. The signal, indicated by the arrow S, may display various sign states: for example, a safe state S 1 allowing passage of the sign, a warning state S2 indicating to act proactively (e.g., reduce speed) or a prohibitory state S3 demanding to stop before the traffic sign 3.

[0030] A detection system 4 for detecting undesired motion of a train is located near the traffic sign 3. The detection system 4 is capable of determining the presence of the train 2, as indicated by arrow D, by means of a detector 5. Further, the detection system 4 comprises a signal generating device 6, or, alternatively, a connection to such device.

[0031] The determination procedure of the present invention is based on determining a path to be traversed by the train based on at least one of its measured motion parameters: e.g., velocity v, acceleration a, their relative change upon approaching the traffic sign 3 and on the distance x between train 2 and standstill position x0... The detection system 4 is arranged for determining braking characteristics of the train 2, and based on these characteristics is arranged for predicting if the train will be able to stop before passing the standstill point x0 at the traffic sign 3.

[0032] The ability of the train to stop at standstill position x0 can be considered using various criteria. For example, the criterion may be the ability to stop before x0 while decelerating at a rate comfortable for passengers or load. Also, the criterion may be the ability for an emergency stop. In general, various combinations of the train's velocity v, acceleration (deceleration) a and distance x to the standstill position x0 may indicate the ability of a stop at the standstill position x0. Moreover, the allowable combinations may depend on the actual location of the traffic sign 3 along the track 1. In the present invention, therefore a certain degree-of-freedom is considered in this respect. A skilled person will appreciate which combinations of ν, α, and x will indicate the ability of a stop.. Below, a more detailed explanation will be given.

[0033] The detection D of a train approaching can be done in various ways, for example, by a radar system, an ultrasound generation and detection system, an optical detection system (equipped with a laser), or a system of sensors arranged on the track. Other systems may applicable as well as known to persons skilled in the art.

[0034] If for some reason, when the traffic sign indicates the stop signal, the engine driver in the train 2 overlooks the signal, the train will pass the traffic sign and enter a prohibited part of the track.

[0035] In the present invention, the detection system 4 of the present invention will detect as described above from the approach of the train 2, whether or not the train 2 will be able to stop before entering the prohibited part of the track 1.

[0036] Upon detection of a failure of the train 2 to stop before or at the standstill position x0, the detection system 4 will activate the signal generating device 6 to generate an alert signal for the engine driver.

[0037] The alert signal is intended for directing the attention of the engine driver towards the stop signal of the traffic sign 3. By observing the alert signal, the engine driver may possibly correct his error before passing the sign, be able to act on the stop signal of the traffic sign, and prevent a possible accident.

[0038] Such an alert signal may be an optical signal, for example a strobe light signal at a high intensity. In that case, the signal generating device 6 of detection system 4 comprises a high intensity lamp which generates a flashing signal. Also, the alert signal may be an audible signal. The signal generating device 6 then comprises an audio generator and some loudspeaker. Other types of alert signal may also be used, for example a wireless communication signal that is transmitted to a mobile receiving unit (not shown) in the engine cabin. Further, such a wireless communication signal may initiate braking to stop the train.

[0039] Figure 2 shows schematically a detection system 4 for detecting undesired motion of a vehicle in accordance with the present invention.

[0040] The detection system 4 may be embodied by e.g., a computer system, a microcontroller, a programmable logic controller, or programmable logic array.

[0041] Functionally, the detection system 4 comprises processing means or host processor 21 with peripherals. The host processor 21 is connected to memory units 18, 19, 22, 23, 24 which store instructions and data. Further the host processor may be connected, if needed, to one or more reading units 30 (to read, e.g., floppy disks 17, CD ROM's 20, DVD's), a keyboard 26 and a mouse 27 as input devices, and as output devices, to a monitor 28 and/or a printer 29.

[0042] Other input devices, like a trackball, a touch screen or a scanner, as well as other output devices may be provided.

[0043] Further, a network I/O device 32 may be provided for a connection to a network 33.

[0044] The memory units shown comprise at least one of RAM 22, (E)EPROM 23, ROM 24, tape unit 19, and hard disk 18. However, it should be understood that there may be provided more and/or other memory units known to persons skilled in the art. Moreover, one or more of them may be physically remote from the processor 21, if required.

[0045] The processor 21 is shown as one box, however, it may comprise several processing units functioning in parallel, or in sequence, or controlled by one main processor, that may be located remotely from one another, as is known to persons skilled in the art.

[0046] The detection system 4 shown in Figure 1 is arranged for performing computations in accordance with the detection method of the present invention.

[0047] Furthermore, the host processor 21 is connected to the traffic sign 3 for receiving a sign state signal as a first traffic input I1. Also, the host processor 21 is connected to a detector 5 for receiving a motion detection signal as a second traffic input I2. Moreover, the host processor 21 is arranged to send communication signals to both the traffic sign 3 and the detector 5, as indicated by the double arrow of the respective connection.

[0048] The sign state signal relates to the sign states S1, S2, S3 indicated by the traffic sign 3. The motion signal from the detector 5 relates to an approach of a train 2.

[0049] Detector 5 implements at least one detection method for detecting a train approaching as mentioned above. The detector 5 is arranged to measure at least one of the train's velocity v, its acceleration a, or its distance x from the standstill position x0 and use that/those as the motion signal.

[0050] The actually used detection method or detector type may depend on the location of the detection system along the track 1. In case of concurrent tracks, depending on the density, for example near a railway station or on a shunting-yard, a specific detection method or detector type for detector 5 may be preferred to obtain signals relating only to the track 1 assigned to the traffic sign 3. A skilled person will appreciate to select a detection method or detector type as preferred by the location along the track.

[0051] Further, the host processor 21 is connected to a signal generating device 6.

[0052] The signal generating device 6 is arranged for receiving a control signal from the host processor 21. Based on the contents of that control signal the signal generating device 6 is arranged for generating an alert signal.

[0053] Persons skilled in the art will appreciate that the detection system 4 as shown here may also be embodied as a boxed micro-electronic device which may be fitted to an existing traffic sign 3. From the traffic sign 3 power may be taken to supply power to the traffic detection system 4.

[0054] The signal generating device 6 may be installed on or in the traffic sign 3, or in its vicinity.

[0055] Figure 3 shows a flow diagram of a procedure 500 for the detection system 4 to carry out a method in accordance with the present invention.

[0056] Procedure 500 starts at a block 505.

[0057] In block 505 some initialisation as known to persons skilled in the art may be carried out by the host processor 21.

[0058] In next block 510, the processor 21 tests if the traffic sign 3 is signalling a stop signal S3. If not, the procedure re-enters block 510.. If the stop signal S3 is active, the procedure continues in block 515.

[0059] Next, in block 515, measurement is performed to detect a presence of a vehicle 2 on the track 1. Such measurement may comprise instructions for reading a detection signal from the detector 5.

[0060] Then, in block 520, the detection signal is tested if a vehicle 2 is approaching on the track 1. If not, the procedure may continue again at block 515 to watch for a vehicle. If a vehicle is approaching, the procedure continues at block 525.

[0061] In block 525, the motion parameters of the vehicle are determined. Either, the detector 5 is instructed to do (time-resolved) measurements at this time, or the motion parameters may be extracted from the detection signal already obtained in block 520. The procedure continues in block 530.

[0062] In block 530, the host processor 21 determines a prediction if the vehicle 2 is able to stop at the standstill position x0. The result of the prediction can be used as a prediction signal for further action by the processing means. The prediction model will be described later in more detail.

[0063] Next, in block 535, the host processor 21 tests if a stop at standstill x0 is feasible. If confirmed, the vehicle will "stay under surveillance": the procedure continues at block 510. If, however, a stop at standstill position x0 is not feasible according to the prediction of block 530, the procedure continues at block 540.

[0064] In block 540, the host processor 21 provides an alert signal to the signal generating device 6. Possibly, other signals are generated as well, for example, for communicating the alert to a traffic control centre.

[0065] Finally, the procedure 500 ends in block 545 or may return to block 500.

[0066] It is noted that alternative procedures are possible which substantially have an equivalent outcome... The procedure 500 illustrated here is based on observation of the track in dependence of the state S1, S2 or S3 of the traffic sign 3.

[0067] An alternative procedure may provide a continuous watch of the track, irrespective of the state of the traffic sign and provide the alert signal in block 540 on the condition that the traffic sign is displaying a stop signal S3.

[0068] Further, the procedure may be arranged to have parallel blocks: for example, a first block for detection of a train approaching and its motion, and a second block for detecting the sign state signal of the traffic sign 3. In such a parallel scheme processing may continue by some block which combines their results. In case a parallel architecture of the traffic detection system is used, such parallel processing may be preferred.

[0069] The prediction model for predicting the feasibility of a successful stop of the vehicle at the standstill position x0 is based on at least one of several motion parameters of the approaching vehicle 2. The motion parameters used in the prediction comprise velocity ν and acceleration (deceleration) a of the vehicle 2, as well as its distance x from the standstill position x0.

[0070] Each of the motion parameters may be measured in some way, or may be derived from some basic measurement. For example, the velocity ν may be measured by a Doppler measurement, but may also be derived from time resolved measurements of the distance x.

[0071] Figure 4 shows a diagram of vehicle speed ν vs distance x to the standstill position x0 to illustrate the method and system of the present invention.

[0072] In a preferred embodiment, the prediction model is based on determining if at least one of the motion parameters is within a range of velocity-distance combinations.

[0073] In Figure 4 a plot is shown of distance x from the standstill position x0 (on horizontal axis) and velocity ν (on vertical axis).

[0074] The plot illustrates a decision strategy for predicting an eventual trespassing, i.e., ignoring of the stop signal S3 at traffic sign 3 by the train.

[0075] A first brake path L1 indicates a relation between velocity v and distance x for a deceleration of the train under normal conditions, i.e., using a braking procedure with a prescribed deceleration to have a normal stop. A normal stop may depend on the actual train type (freight or passengers), i.e., the braking is relatively comfortable the load and /or passengers. Also, a normal stop may be defined in a technical sense: i.e., to have a certain prescribed deceleration under normal operation...

[0076] A second brake path L2 indicates a relation between velocity v and distance x for a deceleration of the train under non-normal conditions, i.e., using a braking procedure with a maximum deceleration. Such maximum deceleration may depend on the actual track condition (for example, being flat or on a slope), the type of vehicle its state of maintenance, external conditions such as the weather, or combinations thereof.

[0077] The shape of the first brake path L1 may be either linear or non-linear depending on the normal braking characteristics of the train. Also, the shape of the second brake path L2 may be either linear or non-linear depending on the braking characteristics of the train. In Figure 4, for reasons of clarity both brake paths L1 and L2 are assumed to be linear.

[0078] The velocity-distance range is divided by first and second brake paths L1, L2 into three regions R1, R2, R3.

[0079] In region R1, the velocity is below the maximum "normal" velocity allowed at the given distance for still having a normal stop at standstill position x0... Based on the motion parameters, the train is approaching in a way which allows a stop with ease. The detection system 4 does not provide an alert signal in this situation.

[0080] In region R2, the velocity is between the maximum "normal" velocity of L1 and the maximum "feasible" velocity which still allows a stop at standstill position x0, albeit the braking is at maximum braking power. Based on the motion parameters, the train is approaching in a way which still allows a stop. The detection system 4 may provide an alert signal in this situation, depending on some predetermined rule which may relate to the situation at the actual location, or to a safety policy of the railroad company.

[0081] Finally, on brake path L2 or in region R3, the velocity of the train 2 at a given distance x is equal to, or respectively above, the maximum "feasible" velocity at that distance. In this situation clearly the approach of the train is dangerous, the detection system 4 will issue an alert signal to alert the engine driver.

[0082] As an example a dotted line T1 is shown which displays the motion of a train which approaches the traffic sign at a continuous velocity ν1. The traffic sign 3 is displaying a stop signal S3. In first region R1 the train may maintain this constant velocity. Then, at distance x1 the train passes the point of a trajectory for a normal stop at x0 with a "normal" deceleration (with the velocity decreasing along first brake path L1).

[0083] If the engine (driver) does not respond, the train may continue at velocity ν1 as indicated by dotted line T2 in second region R2. in this region R2, stopping at standstill position x0 is still possible, although deceleration must be more vigorous than shown by first brake path L1.

[0084] If the engine still does not respond when distance x2 is reached, maximally feasible deceleration may still allow a stop at. Beyond point x2, stopping is no longer possible at standstill position x0.

[0085] As mentioned above, the prediction method may comprise various options when to start to provide the alert signal to the engine driver or when to intercept. Alerting or interception may start in region R1 before crossing the trajectory of L1 or in region R2, directly after passing point x1. Also, it may start at a later stage, at an alerting distance x3 before reaching point x2. (After passing point x2, stopping at standstill position x0 in a safe part of the track 1 is no longer an option, although nevertheless a stop must be made to avoid or minimize any damage). Note that the values of x1, x2 and x3 may depend on the velocity of the train 2.

[0086] As already mentioned above, there is some degree-of-freedom how to interpret the motion parameter(s) that is (are) measured. For example, the behavior of a train that approaches the brake path L1 from first region R1 may indicate from the actual deceleration value that is slowing down and that its trajectory of velocity ν and distance x is going to follow brake path L1. In that case, the train's behavior appears as normal: it can stop at x0.. In Figure 4 this trajectory is indicated by line T4.

[0087] However, a train approaching brake path line L1 from first region may appear to accelerate. In that case, the ν-x trajectory will not tend to follow brake path L1, but may cross it into region R2. Clearly, such behavior indicates that the train is not likely to stop at x0. In Figure 4 this trajectory is indicated by line T5.

[0088] Also, in second region R2, the acceleration/ deceleration of the train may indicate if a stop at x0 may be made. A trajectory T6 of a train braking at somewhat higher deceleration than L1 (and possibly able to stop at x0) is shown in Figure 4.

[0089] Thus, from observation of the acceleration of the train an indication is obtained if the engine driver is responding to the traffic sign or not. Also, this indication may be used as a criterion to generate an alert or interception signal.

[0090] Is noted here that the prediction method can apply various techniques to determine what the outcome of the prediction can be. For example, the prediction method may compare measured motion parameter values with computed ones through a model of equations, or with tabulated values, or with some map. Without any limitation to the scope of the present invention, the prediction method may use any suitable method to relate the measured motion parameter(s) to the possibility that a stop signal of a traffic sign will be ignored.

[0091] It will be noted that the present invention may be practiced in various ways.

[0092] For example, the detection system may be used without regard to a safety velocity threshold above which active braking can be initiated by the detection system or not. The present invention provides a clear advantage at velocities below such a predetermined threshold velocity, since the prior art in some cases does not provide any active interaction of the traffic detection system with a train in that velocity range.

[0093] Also, the traffic detection method according to the present invention may be used for other purposes than providing alerts to the driver of a vehicle. It may also be used to provide information to others, such as train operators or train traffic management authorities.

Claims

1. Traffic detection system (4) for detecting a motion of a vehicle (2) on a track (1), the traffic detection system (4) comprising a traffic sign state detection, the traffic sign state detection being arranged for detecting at least a stop state signal (S3) of a traffic sign (3), the stop state signal indicating to the vehicle to stop at or before a standstill position (x0) at the traffic sign (3),
characterised in that
the traffic detection system (4) further comprises a motion detector (5), the motion detector (5) being arranged for measuring at least one of a set of motion parameters of said vehicle, and the traffic detection system (4) is arranged for determining based on said at least one of a set of motion parameters obtained by the motion detector (5), a prediction signal relating to the vehicle (2) while approaching the traffic sign (3), to predict if during the stop state signal (S3) the vehicle (2) is capable to stop substantially at or before the standstill position (x0).

2. Traffic detection system (4) according to claim 1, wherein the set of motion parameters comprises a velocity (ν) of the vehicle (2), an acceleration (α) of the vehicle (2), and a distance (x) between the vehicle and the standstill position (x0).

3. Traffic detection system (4) according to claim 1, wherein the prediction signal is further determined based on at least one of an actual track condition, a type of vehicle, its state of maintenance and weather conditions...

4. Traffic detection system (4) according to claim 1, 2 or 3 wherein the traffic detection system (4) comprises processing means (21) and memory (18, 19, 22, 23, 24);
the processing means (21) being connected to the memory (18, 19, 22, 23, 24), to the traffic sign (3) for receiving the stop state signal (S3) and to the motion detector (5) for receiving the motion (v, a) of the vehicle (2), the processing means (21) being arranged for performing a computation for the prediction signal.

5. Traffic detection system (4) according to any one of the preceding claims, characterised in that the traffic detection system (4) comprises a signal generating device(6), the signal generating device arranged for receiving the prediction signal and further arranged for providing an alert signal to be communicated to the vehicle (2) if the prediction signal indicates that the vehicle (2) may not be capable to stop substantially at or before the standstill position (x0).

6. Traffic detection system (4) according to claim 5, characterised in that the signal generating device(6) comprises an optical signal generator for generating an optical signal as the alert signal.

7. Traffic detection system (4) according to claim 5, characterised in that the signal generating device(6) comprises an audio signal generator for generating an audio signal as the alert signal.

8. Traffic detection system (4) according to claim 5, characterised in that the signal generating device(6) comprises a communication signal generator for generating a communication signal as the alert signal.

9. Traffic detection system (4) according to claim 8, characterised in that the communication signal is used as a signal for initiating a braking operation by the vehicle.

10. Method for traffic detection for detecting a motion of a vehicle (2) on a track (1), comprising the steps of:

- detecting at least a stop state signal (S3) of a traffic sign (3), the stop state signal indicating to the vehicle to stop at or before a standstill position (x0) at the traffic sign (3),

characterised in that
the method comprises the step of:

- determining, based on measurement of at least one of a set of motion parameters, a prediction signal relating to the vehicle (2) while approaching the traffic sign (3), to predict if during the stop state signal (S3) the vehicle (2) is capable to stop substantially at or before the standstill position (x0).

11. Method for traffic detection according to claim 10, wherein the method comprises the step of providing an alert signal to be communicated to the vehicle (2) if the prediction signal indicates that the vehicle (2) may not be capable to stop substantially at or before the standstill position (x0).

12. Method for traffic detection according to claim 10 or 11, wherein determining
the prediction signal comprises testing if application of a normal deceleration along a first brake path (L1) would allow stopping substantially at or before the standstill position (x0).

13. Method for traffic detection according to claim 10 or 11, wherein the computing of the prediction signal comprises testing if application of a maximally feasible deceleration along the second brake path (L2) would allow stopping substantially at or before the standstill position (x0).

14. Method for traffic detection according to any of the claim 10 - 13, wherein the prediction signal is derived from the motion (v, a) by means of a map using at least a first region (R1) of motion (v) and distance (x) below the first brake path (L1) of normal deceleration, a second region (R2) of motion (v) and distance (x) between the first brake path (L1) of normal deceleration and the second brake path (L2) of maximally feasible deceleration, and a third region (R3) of motion (v) and distance (x) above the second brake path (L2) of maximally feasible deceleration.

15. Method for traffic detection according to claim 14, wherein the provision of the alert signal to be communicated to the vehicle (2) is carried out in dependence on a trajectory of the vehicle (2) within the first region (R1), the second region (R2) or the third region (R3) of the map, the trajectory being such that the vehicle (2) may not be capable to stop substantially at or before the standstill position (x0).

16. Computer system for use in a traffic detection system (4) for detecting a motion of a vehicle (2) on a track (1), the traffic detection system (4) comprising a traffic sign state detection, the traffic sign state detection being arranged for detecting at least a stop state signal (S3) of a traffic sign (3), the stop state signal indicating to the vehicle to stop at or before a standstill position (x0) at the traffic sign (3), the computer system comprising processing means (21) and memory (18, 19, 22, 23, 24); characterised in that
the traffic detection system (4) further comprises a motion detector (5), the motion detector (5) being arranged for measuring at least one of a set of motion parameters of said vehicle,
the processing means (21) is connected to the memory (18, 19, 22, 23, 24), to the traffic sign (3) for receiving the stop state signal (S3) and to the motion detector (5) for receiving the at least one of a set of motion parameters of the vehicle (2),
and the computer system is arranged to enable the traffic detection system (4) to perform:

based on at least one of a set of motion parameters, determining a prediction signal relating to the vehicle (2) while approaching the traffic sign (3), to predict if during the stop state signal (S3) the vehicle (2) is capable to stop substantially at or before the standstill position (x0).

17. Computer program product to be loaded by processing means (21) for use in a traffic detection system (4) for detecting a motion of a vehicle (2) on a track (1), the traffic detection system (4) comprising a traffic sign state detection, the traffic sign state detection being arranged for detecting at least a stop state signal (S3) of a traffic sign (3), the stop state signal indicating to the vehicle to stop at or before a standstill position (x0) at the traffic sign (3), characterised in that
the traffic detection system (4) further comprises a motion detector (5), the motion detector (5) being arranged for measuring at least one of a set of motion parameters of said vehicle,
the processing means (21) is connected to a memory (18, 19, 22, 23, 24), to the traffic sign (3) for receiving the stop state signal (S3) and to the motion detector (5) for receiving the motion (v, a) of the vehicle (2), and
in that the computer program product after being loaded allows the processing means (21) to carry out:

based on the at least one of a set of motion parameters, determining a prediction signal relating to the vehicle (2) while approaching the traffic sign (3), to predict if during the stop state signal (S3) the vehicle (2) is capable to stop substantially at or before the standstill position (x0).

18. Data carrier for computer program product according to claim 17.

Drawing