GB2582936A

GB2582936A - Sensor based trackside train measuring system

Info

Publication number: GB2582936A
Application number: GB1905007.9A
Authority: GB
Inventors: Chadwick Simon
Original assignee: Siemens Mobility Ltd
Current assignee: Siemens Mobility Ltd
Priority date: 2019-04-09
Filing date: 2019-04-09
Publication date: 2020-10-14
Also published as: GB201905007D0

Abstract

A trackside train measuring system (1) for measuring a length (lM-N) of a passing train (100), includes two stationary sensors (11, 12) which are arranged along a train track (200) at a predetermined distance (d) from each other. Both sensors (11, 12) are connected to an analysis unit (13) which calculates the speed (s) of the train (100) by dividing the following values: s = d / (t2 – t1), wherein the time t1 is the time at which a predetermined feature (101, 102, 101’, 102’) of the train (100) passes a first sensor (11) and the time t2 is the time at which the same feature (100) passes the second sensor (12). The length (lM-N) of the passing train (100) is subsequently calculated based on the following equation: lM-N = s * (tM – tN), wherein the time tM is the time at which a predetermined feature (101, 101’) of the train (100) passes one of the two stationary sensors (11, 12) and the time tN is the time at which another predetermined feature (102, 102’) of the train (100) passes the 20 same of the two stationary sensors (11, 12). The sensors (11, 12) may be axle counters, and the total length of the train may be calculated by summing up several measured train portions. A measurement time window (possibly based upon train speed) may be used to set the time over which the length of a given train is sensed.

Description

SENSOR BASED TRACKSIDE TRAIN MEASURING SYSTEM

FIELD OF INVENTION

The present invention relates to a trackside train measuring system for measuring a length of a train. The length is calculated by an analysis unit which cooperates with trackside sensors which sense the passing of a train. The train length, for example, can be used to verify train length information stored in a train control system that was read in from another independent source.

BACKGROUND OF INVENTION

Train control systems are designed to be safety systems which guarantee the integrity of trains on their journey along train tracks. The train tracks might also be occupied by other vehicles and the movement of all trains will have to be controlled such that safety of all the track bound vehicles is never compromised at any time.

In Europe, the European Train Control System (ETCS) standard has been established in the year 2000 and it forms part of the wider European Rail Traffic Management System (ERTMS). The ETCS standard in particular pertains to rail signalling control systems and onboard safety control systems which increase safety for trains travelling across country borders and are confronted with different national railway standards.

ETCS is specified at four different, numbered levels. Level 0 ETCS systems do not interact with trackside equipment due to a missing compliance. Level 1 systems are train based signalling systems that can be superimposed on the existing national signalling systems, thus allowing the already installed national signalling systems to remain in place and use. According to the ETCS Level 1 standard, Eurobalise radio beacons receive signals from trackside signal devices and transmit them to the train as movement authority together with route data at fixed points. The ETCS Level 2 standard relies on a digital radio-based system which transmits movement authority and other signals to the train where they are displayed to the train driver. It is possible to dispense with trackside signalling in principle. However, the train detection and the train integrity supervision still require trackside devices at ETCS level 2 systems.

With Level 3, one could say, ETCS even goes beyond simple train protection.

Trackside train detection devices are no longer required and trains can find their position themselves by means of sensors. Trackside devices typically only receive position reports from the trains on the tracks to determine the state of the tracks. Trains must be capable of determining train integrity by onboard systems at a very high degree of reliability. The route is thus no longer cleared by track sections which are defined with help of the trackside detection equipment, but one train which follows another train can already be granted movement authority up to a point which the previous train has cleared and signalled this to a central radio and control station.

In a level 3 ETCS system without trackside train detection (TTD), the knowledge of the full train length is safety critical since the clearing of a track section must not take place if still some part of a previous train occupies the indicated section. In level 1 or level 2 ETCS systems, the full length of the train is entered into a train control system by the driver manually. Since trackside train detection equipment senses the presence of a train, a faulty entry of this train length is not critical when issuing movement authority to a following train. However, manual entry into a level 3 ETCS train control system increases the risks significantly as trackside equipment cannot provide sufficient security.

Therefore, it exists the need to provide train safety equipment, which overcomes these technical problems, in particular for a level 3 ETCS train control system. In particular, train safety equipment is required which allows the determination of the full train length without interaction with the train driver. Alternatively, safety equipment is required which allows for an automated train length detection. The detected train length could then be used to verify the information which e.g. has been manually entered by the train driver.

SUMMARY OF INVENTION

To address these problems, present invention provides for a trackside train measuring system for measuring a length Im_N (this can be the length of the full train L, or only the length of individual sections of the train which can be added up to calculate the full length L of the train) of a passing train, including two stationary sensors which are arranged along a train track at a predetermined distance d between them, wherein both sensors are connected to an analysis unit to transfer measurement signals from both sensors to this analysis unit which is adapted to calculate the speed s of the train based on the following equation: s = d / (t2 -t1), wherein the time t1 is the time at which a predetermined feature of the train passes a first sensor of the two stationary sensors and the time t2 is the time at which the same feature of the train passes the second sensor of the two stationary sensors; and wherein a length Im_N of the passing train is subsequently calculated based on the following equation: = s * (tM -tN), wherein the time tM is the time at which a predetermined feature of the train passes one of the two stationary sensors and the time tN is the time at which another predetermined feature of the train passes the same of the two stationary sensors. ;The problems are also addressed by a method to operate such a trackside train measuring system described before or hereafter, wherein the method comprises the following steps: - calculating with an analysis unit the speed s of a train passing two stationary sensors which are arranged along a train track at a distance d between the two stationary sensors; - calculating a length Im_N of the passing train subsequently; It is highlighted that the length Im_N of the train does not have to be the full length L of the train. The length Im_N corresponds to the distance between a predetermined feature (e.g. an axle, a wheel or a wheel pair) of the front car (locomotive) and a predetermined feature (e.g. an axle, a wheel or a wheel pair) of the rear car (passenger car, support locomotive, etc.). The length IM-N of the train can be a section of the full train length L, but it may also be identical with the full train length L. However, by measuring a number of individual train lengths Im_N (which are smaller than the full train length L), one is able to calculate the full train length L by e.g. adding all individual train lengths!Rim up. This is in particular the case, if all such individual train lengths Im_N relate to neighbouring sections of the train which all connect to each other. ;If one wishes to calculate the full train length L of the train between the end of the front car (locomotive) and the end of the rear car (passenger car, support locomotive, etc.) the overhangs of the respective cars will typically have to be added, i.e. the distances between the end of the front car and the first predetermined feature of the front car and the distance between the end of the rear car and the last predetermined feature of the rear car. Should, however, the first predetermined feature be identical with the end of the front car and the last predetermined feature be identical with the end of the rear car, the sum of all individual train lengths Im_N will be identical to the full train length L. The invention relies on the principle of sensor based time measurements at the time a predetermined feature of the train passes a track based sensor. Such predetermined features can be any kind of marking fixed to the train. Predetermined features, however, can also be train car components, such as sliding contacts, connectors between individual train cars or wheels or wheel pairs fixed to an axle. ;The sensors will have to be chosen according to the type of predetermined feature of the train which is looked at. The time measurement allows to identify a length of the train by a simple multiplication of a time period with the speed of the train. The speed of the train itself can also be identified using the sensor measurements, thus, allowing for a fully automatic measurement of the full train length or individual sections of it. For clarity it is stated here, that the speed measurements and the respective time measurements can all be carried out with the same set of sensors and during the same time period while the train passes the sensors. ;According to the invention, when a train passes one of the sensors, an interaction between the predetermined feature of the train and the respective sensor leads to the generation of a measurement signal. The measurement signals allow to determine the time at which a predetermined feature passed a certain location, specifically the location of the sensor itself. The time can be identified with the help of an analysis unit which receives the measurement signals. The identified times are subsequently used to determine the length of the train carrying out calculations as described above. ;The calculations described above are simple numerical calculations which can be carried out in very short periods of time, thus, allowing for an online determination of the train length while the train is still passing the sensors. All calculations can be carried out virtually instantaneously (less than a second) so that the train length has been calculated in less than a few seconds after having passed the two sensors. The calculated train length can then be compared to e.g. a value which has been manually inputted into the train control system. ;In order to improve on the accuracy of all calculated parameters, more than two sensors can be arranged along the train track. Sensor measurements can be carried out for a number of neighbouring sensor pairs while the measurements of different pairs are averaged, reducing errors in the parameter calculations. Equally, one can reduce the errors, if the parameters are calculated for a number of different sensor pair measurements first in time and only subsequently averaged. ;Overall, the present invention allows to improve the integrity of the train length information within the train control system, thus reducing the barriers for implementation of the ETCS level 3 standard. ;The invention also allows to use already existing technology, e.g. vibration sensors, inductance sensors, optical sensors, etc. which only need to be installed in a prescribed configuration. With a simple adaptation of the sensor software, the present invention can be realized without significant costs or development times. ;According to one aspect, the two stationary sensors are axle counters and the predetermined features of the train are train wheels which pass by the stationary sensors. The axle counters are able to identify the point in time at which a train wheel passes by the sensor (counter). Typically, axle counters allow to identify the point in time at which a train wheel passes by the axle counter. ;Axle counters are well understood and very rugged trackside equipment. They are very reliable and relatively failure free. Thus, they can build the foundation of a train length measurement system which is important to raise safety. ;According to another aspect of the invention, the time tM is the time at which the first predetermined feature of the train passes one of the two stationary sensors and the time tN is the time at which the last predetermined feature of the train passes the same of the two stationary sensors. The first predetermined feature relates to the feature which interacts with the identified sensor first in time and the last feature relates to the feature which interacts with the sensor last in time, assuming all features correspond to the same train. E.g. is the predetermined feature a wheel, the first feature relates to the first wheel (or wheel pair) of the first train car (locomotive) viewed in regular travelling direction. Similarly, the last feature relates to the last wheel of the last train car, also view in regular travel direction of the train. ;Is the speed of the train relatively constant, the full length of almost the entire train can be identified with only two measurements. This allows for a very quick and simple determination of the train length. Adjustments to the calculated length of the entire train to obtain the full train length (L) can be made and are explained further below. ;According to another aspect of the invention, the length of the train is added to at least one constant value to result in the full length of the train. It is highlighted again, that the full length of the train relates to the distance between the end of the front car of the train (locomotive) and the end of the rear car of the train, thus covering all parts of the train. In contrast, the length of the train calculated according to present invention does not need to cover the entire extension of the train length. In other words, the full length of the train typically requires the addition of an overhang accounting for the distance between the front end of the front car and the first predetermined feature and the rear end of the rear car and the last predetermined feature. ;The calculated train length can also be shorter when compared to the full length of the train, e.g. because certain parts of the train cannot be measured. This is in particular true for the distance between the front end of the train and the first predetermined feature, or the rear end of the train and the last predetermined feature, assuming that both features are not fixed to the front end and the rear end respectively. Are the predetermined features the wheels or wheel pairs of the train cars and the sensors axle counters, one may infer from the wheel base the adjustments to calculate the full length of the train. Calculated adjustments can be added to the measured and subsequently calculated length of the train. The adjustments typically depend on the type of train and may e.g. be readily taken from a data base which stores information about the train geometry and the predetermined feature location. ;According to another aspect, a length of the train is further calculated by adding at least two individual lengths for two different sets of predetermined features. In particular, the two different sets of predetermined features are neighbouring sets of predetermined features which mark out sections which in particular contact each other. Further, both pairs of predetermined features may share one predetermined feature. ;In the case of the predetermined features being wheels or wheel pairs passing by or over an axle counter, the two sets of different features relate to two different sets of wheels or wheel pairs, e.g. the first and second wheels or wheel pairs in the sense of a first set and the second and third wheels or wheel pairs in the sense of a second set of predetermined features. If the measured and calculated train lengths are added up for all sets of neighbouring wheels or wheel pairs in this sense, the full train length can be calculated. As mentioned before, small adjustments for the wheel base i.e. the location of the first and last wheels or wheel pairs of the train can be added to derive the full length of the train. ;Here, it should be highlighted that in the context of the entire description, the functioning of the axle counter typically only relies on a single wheel which is detected. Hence, if an axle counter is employed as stationary sensor, the passing of a wheel and the passing of a wheel pair have the same technical effect. ;According to another aspect of the invention, the analysis unit provides for a timeout operation, which allows to identify a measurement window during which the two stationary sensors transmit measurements and the analysis unit carries out the calculations of the train length. During regular operation, i.e. within the measurement window the analysis unit receives and uses the sensor signals in its calculations, during timeout operation, e.g. after the train has passed both sensors, no further signals are received and/or used for calculation by the analysis unit. A timeout operation, thus, prevents miscalculation of the train length by obtaining and considering faulty signals which e.g. do not result from an event which is desired to be detected. Time out operations might also occur if the train stops during measurement, moves very slowly or changes direction. ;Further, the timeout operation can be dependent on the train speed s and/or the maximum expected separation of predetermined features in time or in space. In particular, the time window length during which normal operation prevails is dependent on the train speed s and/or the maximum expected separation of predetermined features. Using these train parameters, allows for a simple and effective determination of the window in which the analysis unit operates normally and the timeout operation times. ;According to another aspect, the analysis unit provides for an updated calculation of the train speed s when a subsequent predetermined feature of the train passes the sensors. In particular, an updated calculation of the train speed s is provided each time when consecutive and/or neighbouring predetermined features of the train pass a respective sensor, thus, allowing to calculate individual train lengths always with the most recently determined train speed s. This reduces inaccuracies due to a change in train speed s, i.e. when the train accelerates or decelerates. Thus, by splitting the calculation of the train length into individual calculations of smaller train lengths, corresponding to sections of the train length, a change in train speed can be accounted for. Mathematically, the calculation which is carried out by the analysis unit imitates a numerical integration of smaller, individual train lengths with a changing train speed. The larger the change in train speed, the more significant a split-up calculation of the train length becomes in order to obtain a reliable result. ;According to another aspect, the analysis unit also determines the direction of a passing train, in particular using the sensor measurements with which the speed s of the train is calculated. To identify the direction, the analysis unit identifies which of the two sensors has been passed in time first and which one has been passed second. From this time information, the direction of the passing train is readily inferred. The calculation of the train direction is another security relevant feature, which allows to increase overall safety by the train control system. ;According to another aspect, the analysis unit is adapted to initiate an alarm in case the two stationary sensors do not detect the same number of measurement signals within a predetermined time window. The alarm is in particular initiated after it has been established by the train control system that the train decelerates and possibly will come to a stop before it has passed the two stationary sensors. Does the train indeed come to a stop before its full length passes the sensors the trackside train measuring system allows to determine that fact and the analysis unit will initiate an alarm as the stopped train can pose a danger for other vehicles on the train tracks. The length of the predetermined time window depends in particular on the speed s of the train. Is the speed of the train relatively small, the window will have to be selected relatively larger when compared to the window length of a relatively faster train. ;According to another aspect, the two stationary sensors are arranged on the train track not further than lkm away from a location where splitting operations, shunting operations or joining operations are carried out. Such operations are typically only carried out in determined locations of the track network. The locations typically are near a train station or a train depot. These operations change the length of the train and thus bear a potential for risk if e.g. the train length information is not put correctly into the train control system. ;Further, the analysis unit is connected to a train control system, wherein the train control system is in particular adapted to receive a signal indicating an expected arrival time of a train, and wherein the train control system generates a first alarm signal if either no train arrives at the indicated time or it generates a second alarm if a train arrives without the train control system having received a prior signal indicating the expected arrival time of the train. In both cases errors of the train control system can be the reason or they can indicate a train problem. Both incidences bear risks for the rest of all vehicles on the tracks. ;Alternatively, the analysis unit is connected to a train control system, wherein the train control system is adapted to receive a first signal indicating the direction of occupation of the train track and a subsequent, second signal indicating a measurement of the length of the train or a subsequent error message indicating a problem with measuring the train length. This will allow to determine if the stationary sensors detected an occupation of the train track and an alarm could be initiated if the train tracks were still occupied. In case a train passes the stationary sensors, the direction of occupation can be identified by comparing which of the both sensors measure the train movement first. Subsequently, the length of the train will be measured and a signal is sent to the control system indicating the ongoing measurement or a concluded measurement. The train track will be considered clear if the measurement of a direction of occupation and the train length will have been concluded and respective signals will have been received by the control system. If there was a problem with measuring the length of the train, the second signal would be an error message. If such error message was received by the control system, the respective section of the train tracks could not be cleared. ;Further, the two stationary sensors can be arranged on the train track at the border of a level 3 ETCS control area; this would allow the trackside train measuring system to keep all trains identified which enter and exit the level 3 ETCS control area. The knowledge of the train locations helps to maintain the necessary high security level within the level 3 ETCS control area. ;BRIEF DESCRIPTION OF THE DRAWINGS ;The above mentioned attributes and other 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 of an embodiment of the trackside train measuring system in a view from the side FIG. 2 shows a flow diagram of one embodiment of the inventive method for operating a trackside train measuring system; ;DETAILED DESCRIPTION OF INVENTION ;Figure 1 shows a schematic drawing of one embodiment of the trackside train measuring system 1 for measuring a length INI_N of a passing train 100. The length Inn_ N relates to a section of the front car (locomotive) of the train 100. The trackside measuring system 1 is designed to calculate the length INI_N of the passing train 100 without further manual interference e.g. by a train driver. ;The trackside train measuring system 1 has two sensors 11, 12 which are arranged along a train track 200 at a predetermined distance d between them. The two sensors 11, 12 are fixed to the tracks 200 or to the ground and remain stationary. Both sensors 11, 12 are connected to an analysis unit 13. The measurement signals generated by both sensors 11, 12 are transferred to the analysis unit 13 where the signals are analysed. The analysis unit 13 can receive raw data or pre-analysed information. Should it receive pre-analysed data, the stationary sensors 11, 12 will to include a pre-analysis unit. ;To calculate the momentary speed s at the time the train 100 passes over the stretch between both sensors 11, 12, the first of the two sensors 11, 12 is activated when the first train wheel 101, in the sense of the first predetermined feature 101 rolls over it. The sensors 11, 12 are axle counters and are adapted to detect the wheel of the train 100 passing. The sensors 11, 12 allow to determine the time t1 when the first wheel 101 passed the sensor 11. Similarly, the time t2 can be determined when the same first wheel 101 passes by or over the second sensor 12. ;With the knowledge of the distance d between both sensors 11, 12, the speed of the train 100 can be calculated in a very simple calculation based on the following equation 1: s = d / (t2-ti) (Equation 1) The first wheel 101 is identical with a first predetermined feature 101 of the train 100. This feature 101, however, could be any form of marker which in combination with the two stationary sensors 11, 12 allows the determination of the times at which the respective feature 101 was present at a specific location, in particular at the location of the sensor 11, 12. ;The speed s of the train 100 can be variable, i.e. the train can accelerate or decelerate. In case of a variable speed s, the calculated speed is an average speed. ;After the speed s of the train has been established, the length Im_N of the train 100 can subsequently be calculated based on the following equation 2: IM-N = S * (tM tN) (Equation 2) wherein the time tM is the time at which the first wheel 101 of the train 100 passes one of the two stationary sensors 11, 12 and the time tN is the time at which the second wheel 102 of the train 100 passes the same of the two stationary sensors 11, 25 12.

In order to increase the accuracy of the calculation, the length Im_N of the train 100 may also be calculated for both sensors 11 and 12 and the average of both calculated values will yield the calculated train length Im_N. In order to increase the accuracy even further, another pair of sensors 11, 12 could be arranged next to the already existing pair 11, 12, thus, increasing the overall result space.

The calculation of the train length Im_N yields in present embodiment the distance between the first two wheels 101 and 102 of the train. Subsequently, the calculation can again be carried out for the next set of wheels 101' and 102' of the train. The first wheel 101' of this new set is identical with the second and last wheel 102 of the previous set 101, 102. The second wheel 102' in the new set, however, is a wheel which has not been used in previous calculations. The new calculations yield a new train length Inho, which for example can be added to the already calculated train length IM-N. This addition is typically carried out in the analysis unit, but can also be carried out in the train control unit.

The calculation for the new set of wheel pairs 101' and 102' can also make use of an updated calculated speed s of the train. In case that for each wheel set the speed s of the train is updated, changes in the train speed s during the calculation of the full length L of the train 100 can be accounted for. Thus, a variable train speed s does not impede the determination of the full train length L (not shown in the figure).

Adding all lengths IM-N, IN-0 for the train 100 results in the length of the train. Only the train sections between the front end of the first car of the train 100 (shown here) and the first wheel 101, and the section between the end of the rear end of the last car of the train 100 (not shown here) and the last wheel cannot be accounted for. These lengths, also known as overhangs, however, may be added to the overall result by a simple addition of a constant value a (here, only accounting for the adjustment to the front end of the train car) to the sum of all lengths IM-N, IN-0 calculated for the train 100.

According to present embodiment, the analysis unit 13 is connected to a train control system 14. The train control system 14 is adapted to receive a signal indicating an expected arrival time of a train. The train control system 14 can also generate a first alarm signal if either no train 100 arrives at the indicated arrival time or it generates a second alarm if the train 100 arrives without the train control system 14 having received a prior signal indicating an expected arrival time.

Figure 2 shows a flow diagram of one embodiment of the inventive method for operating a trackside train measuring system 1 as described before. The method comprises the following steps: - calculating with an analysis unit 13 the speed s of a train 100 passing two stationary sensors 11, 12 which are arranged along a train track 200 at a distance d between the two stationary sensors 11, 12 (first method step 301); calculating a length Im-N of the passing train 100 subsequently (second 5 method step 302);

Claims

CLAIMS1. A trackside train measuring system (1) for measuring a length (Im-N) of a passing train (100), including two stationary sensors (11, 12) which are arranged along a train track (200) at a predetermined distance (d) between them, wherein both sensors (11, 12) are connected to an analysis unit (13) to transfer measurement signals from both sensors (11, 12) to this analysis unit (13) which is adapted to calculate the speed (s) of the train (100) based on the following equation: s=d/(t2-ti), wherein the time ti is the time at which a predetermined feature (101, 102, 101', 102') of the train (100) passes a first sensor (11) of the two stationary sensors (11, 12) and the time t2 is the time at which the same feature (101, 102, 101', 102') of the train (100) passes the second sensor (12) of the two stationary sensors (11, 12); and wherein the length (IM-N) of the passing train (100) is subsequently calculated based on the following equation: Im_N = s * (ti -tN), wherein the time tM is the time at which a predetermined feature (101, 101') of the train (100) passes one of the two stationary sensors (11, 12) and the time tN is the time at which another predetermined feature (102, 102') of the train (100) passes the same of the two stationary sensors (11, 12).
2. A trackside train measuring system according to claim 1, characterized in that the two stationary sensors (11, 12) are axle counters and the predetermined features (101, 102, 101', 102') of the train (100) are train wheels which pass by the stationary sensors (11, 12).
3. A trackside train measuring system according to one of the previous claims, characterized in that the time tM is the time at which the first predetermined feature (101, 101') of the train (100) passes one of the two stationary sensors (11, 12) and the time tN is the time at which the last predetermined feature (102, 102') of the train (100) passes the same of the two stationary sensors (11, 12).
4. A trackside train measuring system according to one of the previous claims, characterized in that a length of the train (100) is added to at least one constant value (a) to result in the full length (L) of the train (100).
5. A trackside train measuring system according to one of the previous claims 1 or 2, characterized in that the length (Im_N) of the train (100) is further calculated by adding at least two individual lengths (Im_N, Iwo) for two different sets of predetermined features (101, 102, 101', 102').
6. A trackside train measuring system according to one of the previous claims, characterized in that the analysis unit (13) provides for a timeout operation, which allows to identify a measurement window during which the two stationary sensors (11, 12) transmit measurements and the analysis unit (13) carries out the calculations of the train length (IM-N).
7. A trackside train measuring system according to claim 6, characterized in that the timeout operation is dependent on the train speed (s) and/or the maximum expected separation of predetermined features in time or in space.
8. A trackside train measuring system according to one of the previous claims, characterized in that the analysis unit (13) provides for an updated calculation of the train speed (s) when a subsequent predetermined feature (101', 102') of the train (100) passes the sensors (11, 12).
9. A trackside train measuring system according to one of the previous claims, characterized in that the analysis unit (13) also determines the direction of a passing train (100) using the sensor measurements with which the speed (s) of the train (100) is calculated.
10. A trackside train measuring system according to one of the previous claims, characterized in that the analysis unit (13) is adapted to initiate an alarm in case the two stationary sensors (11, 12) do not detect the same number of measurement signals within a predetermined time window.
11. A trackside train measuring system according to one of the previous claims, characterized in that the two stationary sensors (11, 12) are arranged on the train track (200) not further than 1km away from a location where splitting operations, shunting operations or joining operations are carried out which change the length of the train (100).
12. A trackside train measuring system according to one of the previous claims, characterized in that the analysis unit (13) is connected to a train control system (14), wherein the train control system (14) is adapted to receive a signal indicating an expected arrival time of a train, and wherein the train control system (14) generates a first alarm signal if either no train (100) arrives at the indicated time or it generates a second alarm if a train (100) arrives without the train control system (14) having received a prior signal indicating the time as the expected arrival time of the train (100).
13. A trackside train measuring system according to one of the previous claims 1 to 11, characterized in that the analysis unit (13) is connected to a train control system (14), wherein the train control system (14) is adapted to receive a first signal indicating the direction of occupation of the train track (200) and a second, subsequent signal indicating a measurement of the length (Im_N) of the train (100) or a subsequent error message indicating a problem with measuring the train (100) length (INA_N).
14. A trackside train measuring system according to one of the previous claims, characterized in that the two stationary sensors (11, 12) are arranged on the train track (200) at the border of a level 3 ETCS control area;
15. A method to operate a trackside train measuring system (1) according to one of the previous claims, comprising the following steps: - calculating with an analysis unit (13) the speed (s) of a train (100) passing two stationary sensors (11, 12) which are arranged along a train track (200) at a distance (d) between two stationary sensors (11, 12); calculating a length (Im_N) of the passing train (100) subsequently;