GB2622872A - Trackside worker warning method - Google Patents

Abstract

A method (100, fig. 3) of warning a trackside worker 1 or personnel nearby a railway of the approach of a train 4 along a rail track 2. Initially, an acoustic signal S indicating the movement of a train along a rail track toward a trackside worker is detected (102, fig. 3) using a portable signal detector 3. Next, the signal is processed (104, fig. 3) to determine the speed s of the train and distance d2 from the trackside worker. If the speed of the train or the distance from the trackside worker exceeds a pre-determined threshold, then a wearable alarm 6 worn on the trackside worker is triggered (106, fig. 3) to warn the trackside worker of the approaching train. Also disclosed is a portable signal detector comprising a housing (7, fig. 4a), a sensor (9, 21, fig. 4a) and a processor (29, fig. 4b).

Description

TRACKSIDE WORKER WARNING METHOD

The present invention relates to method of warning a trackside worker proximate a railway of the approach of a train along a rail track, and a system adapted to provide such a warning.

For trackside rail workers in the United Kingdom, the biggest cause of work-related fatalities is being struck by a train whilst working on or alongside the rail track. In all cases either the train driver is unable to stop the train before reaching the rail workers or the rail workers fail to realise that a train is approaching. Modern rolling stock is designed to achieve as low friction as possible between the wheels of a train and the train track, since this increases the efficiency of the train when up to speed. Since the course of the train is constrained by the rail tracks and the distance that a train driver can see is constrained by trackside objects and track direction, if a person is seen on the tracks the emergency braking capability of the train is a large factor in avoiding an accident. Where friction is reduced for efficiency purposes, emergency breaking will take longer. For high speed trains, the breaking distance may be over half a kilometre at 160km/h, meaning that significant visibility is required. In addition, the breaking relies on the reaction time of the train driver, which may add to the overall stopping distance.

In the situation where a trackside worker fails to realise that a train is approaching several factors are involved. Firstly, the low friction requirement in conjunction with the widespread use of continuously-welded rails reduces the audible noise generated by a train, since the traditional "clickety-clack" noise may be absent and vibrations along the rail may be reduced. Secondly, and particularly where heavy engineering apparatus is in use, a rail worker may not hear a train horn, since the sound intensity of the train horn is lower than that of the combination of heavy engineering equipment and hearing protec-tion.

A number of "safe systems of work" exist to enable work to be carried out on the railway whilst ensuring trackside worker safety. In the UK, these include: * Safeguarded: all lines a blocked; * Fenced: a fence is erected between the site of work and the nearest open line; * Equipment warning: o Automatic Track Warning System (ATWS): uses lights, sirens and/or a personal warning device; o Train Operated Warning System (TOWS): uses sirens; o Lookout Operated Warning System (LOWS): uses lights, sirens and/or a personal warning device triggered by a lookout; * Lookout warning: a lookout warns of oncoming trains using a horn, whistle or torch; and * "Site Warden" warning: a space is provided between the site of work and the nearest open line and a Site Warden watches to make sure everyone working re-mains in the safe area.

Despite these measures, fatalities still occur. It is necessary, therefore, to be able to give trackside workers sufficient warning of an approaching train that they can move away from any danger areas to a place of safety in good time before the train reaches 15 them.

The present invention aims to address these issues by providing, in a first aspect, a method of warning a trackside worker proximate a railway of the approach of a train along a rail track, comprising the steps of: a) detecting a signal indicating the movement of a train along a rail track toward a trackside worker using a portable signal detector; b) processing the signal to determine the speed of the train and distance from the trackside worker; if the speed of the train and/or the distance from the trackside worker exceed a pre-determined threshold, c) triggering a wearable alarm worn on the trackside worker to warn the trackside worker of the approaching train.

Unlike some existing track protection systems, which rely on a train being fitted with a device to alert the system of its approach or a unit having an interface with existing systems such as the control centre, the use of the portable signal detector can simply be placed where needed to detect approaching trains, without the need for any train interface changes.

Preferably, the portable signal detector is located at the same location as the trackside worker.

Preferably, the signal comprises acoustic waves generated by a train, and wherein the step of processing comprises: i) determining a first signal intensity // of the train at a first point in time ti; ii) retrieving a reference signal power PR of the train from a storage device; iii) calculating a first distance d1 the train is from the trackside worker based on the first signal intensity // and the sound power PR.

Preferably, the step of processing further comprises: iv) repeating steps i) to Hi) at a second point in time tzto determine a second distance d2 the train is from the trackside (a2-ao worker; v) calculating the speed s of the train using s = (t2-t1) The signal may comprise airborne acoustic waves generated by a train horn. In this case the portable signal detector preferably comprises a microphone.

The signal may comprise rail-borne acoustic waves generated by train wheels. In this situation, the portable signal detector preferably comprises a vibration sensor.

The signal may comprise an acoustic signature characteristic of a train. In this case, preferably the method further comprising the step of: using the portable signal de- tector to record acoustic signatures to create training data for a machine-learning pro-gram.

Alternatively, the signal may comprise a visual signal indicative of a train.

The step of triggering wearable alarm may comprise: i) sending a signal from the portable signal detector to a central control centre warning of the approaching train; and ii) sending a signal from the central control centre to the wearable alarm to trigger an alarm. Alternatively, the step of triggering wearable alarm may comprise: i) sending a signal from the portable signal detector to the wearable alarm to trigger an alarm.

Preferably, the wearable alarm comprises a vibration motor, light source and/or audible alarm.

The present invention also provides, in a second embodiment, a portable signal detector adapted to detecting a signal indicating the movement of a train along a rail track toward a trackside worker, comprising: a housing; a sensor adapted to detect a signal indicating the movement of a train along a rail track toward a trackside worker; and a processor adapted to process the signal to determine at least a first signal intensity // at a time ti for comparison with a reference source power PR to indicate the speed of the train and distance di the train is away from the trackside worker.

The present invention will now be described by way of example only, and with reference to the accompanying drawings, in which: Figure 1 is a schematic diagram of a train approaching a trackside worker using a method of warning in accordance with embodiments of the present invention; Figure 2 is a schematic diagram of a train approaching a trackside worker using a method of warning in accordance with embodiments of the present invention at a time t after Figure 1; Figure 3 is a flowchart of a method in accordance with the embodiments of the present invention; Figure 4a is a schematic diagram of a first portable signal detector used in conjunction with the embodiments of the present invention; Figure 4b is a schematic diagram of a second portable signal detector used in conjunction with the embodiments of the present invention; and Figure 5 illustrates a typical train acoustic signature in a frequency domain.

The present invention takes the approach of using automatic signal detection and processing to determine the speed and presence of an approaching train with a direct warning to a trackside worker. A signal indicating the movement of a train along a rail track toward a trackside worker is detected using a portable signal detector. The signal is processed to determine the speed of the train and distance and direction from the track- 2 0 side worker. This may be done in a variety of ways, either by the signal detector or re- motely in a central control centre or by utilising cloud-based services. If the speed of the train and/or the distance and direction from the trackside worker exceed a pre-determined threshold, a wearable alarm worn on the trackside worker is triggered to warn the trackside worker of the approaching train. This will now be explained in more detail be-low.

Figure 1 is a schematic diagram of a train approaching a trackside worker using a method of warning in accordance with embodiments of the present invention. A track-side worker 1 is performing maintenance tasks on a rail track 2 at a location Pi. A portable signal detector 3 is located proximate to the trackside worker 1, and adapted to de- tect a signal indication the movement of a train 4 along the rail track 2 towards the track-side worker 1. In Figure 1, the train 4 is shown at a distance ch from the portable signal detector 3 located at Pi. At this distance, the portable signal detector 3 detects a signal with a first signal intensity h, which corresponds to a reference signal power PR of the train 4. Figure 2 is a schematic diagram of a train approaching a trackside worker using a method of warning in accordance with embodiments of the present invention at a time t after Figure 1. Now the train 4 has moved closer to the portable signal detector 3 as indi-cated by d2, such that the portable signal detector 3 detects a second signal intensity '2, which corresponds to a second reference signal power PR of the train 4.

Figure 3 is a flowchart of a method in accordance with the embodiments of the present invention. The method 100 comprises a first step 102 of detecting a signal S indi- 1 0 cating the movement of a train 4 along a rail track 2 toward a trackside worker 1 using a portable signal detector 3. Next, at step 104, the signal S is processed to determine the speed of the train and distance and direction from the trackside worker. As an example, the signals comprises acoustic waves generated by the train 4, which may be an airborne acoustic signal, such as a horn or an acoustic signature corresponding to the noise of the train wheels 5 crossing expansion points, points or rail joints as the train 4 travels along the rail track 2. The signal may be rail-borne, generated by the train wheels 5 in contact with the rail track 2. Often this noise is known as "ringing". In other embodiments, the signal may be a visual signal indicative of a train, and comprise a video image of the train. The signals is analysed to determine a first signal intensity // of the train 4 at a first point in time ti. This signal intensity // corresponds to a reference signal power PR of the train 4 that is stored in a storage device. The storage device may be part of the portable signal detector 3, or may be accessed remotely, such as via a cellular connection to a remote server or to a cloud-based server. The reference signal power PR is preferably stored in a database, lookup table or similar. Once the reference signal power PR of the train has been retrieved from the storage device, a first distance di the train is from the trackside worker 1 based on the first signal intensity // and the signal power PR is calculated. For an acoustic signal, this is done using the inverse square law relationship between sound power P and distance d: / = 47rd2 where / is the sound intensity, P is the sound or signal power and d is the distance be-tween the train 4 and the portable signal detector 3. Therefore, the first signal intensity h leads to a determination of a first distance d1 that the train 4 is from the trackside worker 1. For a visual signal, image processing may be used to analyse the number of pixels corresponding to the image of a train, and thus create a signal intensity for which there is simple linear correlation with the reference signal power Pr.

At this point, the distance d1 may be compared to a threshold distance, regardless of the speed of the train 4, and at step 106 used to trigger a wearable alarm 6 worn by the trackside worker 1. Alternatively, it may be desirable to determine the speed of the train 4 as part of the warning process. This is done at a second time t2, which occurs at a time t after ti, where the signals is detected, analysed to determine a second signal in-tensity /2 and the second reference signal power PR is retrieved from the storage device.

This enables the calculation of the second distance d2 that the train 4 is from the trackside worker 1, and the speed of the train s calculated using: (d2 -d1) S = (t2 -tl) The combination of the speed s of the train 4 and the second distance d2 may then be used to trigger the wearable alarm 6 on the trackside worker 1. Alternatively, the second distance d2 may be calculated based on the ratio of the first signal intensity // to the second signal intensity /2 to avoid needing to retrieve a second reference signal power PR from the storage device.

Figure 4a is a schematic diagram of a first portable signal detector used in conjunc-tion with the embodiments of the present invention. This represents a simple portable signal detector 3, which can be deployed easily either proximate to the location of the trackside worker 1 or at the location of the trackside worker 1. The portable signal detector 2 comprises a housing 7 mounted on a base 8. For embodiments of the present invention where air-borne signals are used to determine the approach of a train 4, the port-able signal detector 3 is adapted to be placed on the ground with the bases in contact with either ballast, concrete, grass or other substrate material. An acoustic sensor 9 is positioned within the housing 7 to detect air-borne acoustic signals. The acoustic sensor 9 is connected to a power source manager 10 via a switch 11, an input filter 12 and a signal amplifier 13. The acoustic signal is passed firstly to the input filter 12 and then to the signal amplifier 13 before being input to a processor 14, such as an integrated chip. A mi-crocontroller 15 controls both the switch 11 and the processor 14, and is connected to the power source manager 10. The acoustic signal is processed by the processor 14, and the microcontroller 15 inputs to a switch 16, which is connected to the power supply 17, also operated by the power source manager 10, before being transmitted to a remote server 18 by a transmitter 19 for processing. The power source manager 10 is also con-nected to a battery 20 in case the power supply 17 should fail. For embodiments of the present invention that employ rail-borne sensing, the acoustic sensor 9 is replaced with a vibration sensor 21. Suitable acoustic sensors include microphones, transducers and piezoelectric acoustic wave sensors. Suitable vibration sensors include displacement sensors, velocity sensors and accelerometers. For embodiments of the present invention employing a visual signal, the acoustic sensor is replaced with an image detector, such as a CCD or CMOS device.

Since the portable signal detector 2 is a relatively simple design, the storage device for reference signal power PR and the processor for carrying out the various calculations to determine train 4 distance and speed are carried out remotely. This may be done by a remote server located in a central facility or using cloud-based storage and processing. In both cases the signal transmitted by the transmitter 19 is received by a receiver and signal processor, and then routed via a bus or wireless connection to the processor. The processor retrieves information from the storage device as required. The orientation of the portable signal detector 3 may be used to determine the direction the train is ap- 2 0 proaching in, or alternatively, a second acoustic sensor 9 may be provided and the iden-tity of the acoustic sensor with the strongest signal used to determine the direction. Once the train 4 speed and/or distance has been calculated, the processor compares these against a threshold based on the time taken for a trackside worker 1 to retreat to a safe position. If the threshold is met or exceeded, the processor triggers the wearable alarm 6 worn by the trackside worker 1 by sending a signal to the wearable alarm 6, which then alerts the trackside worker 1. This may be by vibrating, sounding an alarm, flashing a light or a combination of all three.

Figure 4b is a schematic diagram of a second portable signal detector used in conjunction with the embodiments of the present invention. The embodiment of the present invention illustrated in Figure 4a requires a good cellular connection to the remote or cloud-based server in order to process the signals detected by the portable signal detector 3. The embodiment of the present invention shown in Figure 4b may be used when such a connection cannot be guaranteed. The portable signal detector 3 can be deployed easily either proximate to the location of the trackside worker 1 or at the location of the trackside worker 1. The portable signal detector 2 comprises a housing 22 mounted on a base 23. For embodiments of the present invention where air-borne sig-nals are used to determine the approach of a train 4, the portable signal detector 3 is adapted to be placed on the ground with the base 23 in contact with either ballast, concrete, grass or other substrate material. An acoustic sensor 24 is positioned within the housing 22 to detect air-borne acoustic signals. The acoustic sensor 22 is connected to a power source manager 25 via a switch 26, an input filter 27 and a signal amplifier 28. The acoustic signal is passed firstly to the input filter 27 and then to the signal amplifier 28 before being input to a processor 29, such as an integrated chip. In this embodiment, the integrated chip 29 is connected to a storage device 30 with read-write capabilities. A microcontroller 31 controls the switch 26, the processor 29 and storage device 30, and is connected to the power source manager 25. The acoustic signal is processed by the pro- cessor 29, and the microcontroller 31 inputs to a switch 32, which is connected to the power supply 33, also operated by the power source manager 25. The power source manager 25 is also connected to a battery 34 in case the power supply 33 should fail. For embodiments of the present invention that employ rail-borne sensing, the acoustic sen- 2 0 sor 24 is replaced with a vibration sensor 35. The orientation of the portable signal detec- tor 3 may be used to determine the direction the train is approaching in, or alternatively, a second acoustic sensor 24 may be provided and the identity of the acoustic sensor 24 with the strongest signal used to determine the direction. Suitable acoustic sensors include microphones, transducers and piezoelectric acoustic wave sensors. Suitable vibra- 2 5 tion sensors include displacement sensors, velocity sensors and accelerometers.

In this embodiment, data relating to the reference signal power PR is stored in the storage device 30, and calculations are carried out using the processor 29. There is no need to transmit or receive data from remote servers whilst deployed, as data is stored within the portable signal detector 3. Information can be loaded onto the storage device 30 before deployment of the portable signal detector 3. In addition, the portable signal detector 3 can be used to record train 4 acoustic signatures to create training data to train machine learning programs to recognise individual acoustic signatures. The processor 29 is also used to send a signal from the portable signal detector 3 to the wearable alarm 6 worn by the trackside worker 1 to trigger the alarm, using a transmitter 36. Figure 5 illustrates a typical train acoustic signature in a frequency domain. The acoustic signature 37 is made up of two distinct components: a series of closely spaced peaks 38, corresponding to the wheelsets of the train bogeys contacting a feature on the rail, such as an expansion gap; and a frequency envelope 39, the slope of which indicates the speed of the train 4. Such an acoustic signature is useful where either there are known features the train will encounter along the route, or where a target is placed on the rail track 2 to generate an acoustic signal.

Other alternative sensors to replace either the acoustic sensor 9, 24 or the vibration sensor 21, 35, include voltage detectors (arranged to detect a voltage drop in either an overhead wire or third rail) and image sensors (adapted to detect movement on a specific rail track 2). Each of these alternative sensors can be used with the portable signal detector 3 to trigger an alarm on the wearable alarm 6 worn by a trackside worker 1 in the same manner as the embodiments above.

Unlike some existing track protection systems, which rely on a train 4 being fitted with a device to alert the system of its approach or a unit having an interface with existing systems such as the control centre, the embodiments of the present invention do not re-quire any interfaces and can simply be placed where needed to detect approaching trains 4. The wearable alarm 6 can be triggered based on the ringing in the rails typically observed by observed by trackside workers 1 a significant amount of time before a train appears in view. Trackside workers 1 can be notified of the speed, distance away and direction of a train 4 easily. In addition, the opportunity for human error is minimised, as the embodiments of the present invention may be used in addition to or instead of a lookout.

Claims (1)

1. CLAIMS1. A method of warning a trackside worker proximate a railway of the approach of a train along a rail track, comprising the steps of: a) detecting a signal indicating the movement of a train along a rail track toward a trackside worker using a portable signal detector; b) processing the signal to determine the speed of the train and distance from the trackside worker; if the speed of the train and/or the distance from the trackside worker exceed a pre-determined threshold, c) triggering a wearable alarm worn on the trackside worker to warn the trackside 2. Method as claimed in claim 1, wherein the portable signal detector is located at the same location as the trackside worker.3. Method as claimed in claim 2, wherein the signal comprises acoustic waves gener-ated by a train, and wherein the step of processing comprises: i) determining a first signal intensity Ii of the train at a first point in time ti; ii) retrieving a reference signal power PR of the train from a storage device; iii) calculating a first distance d/ the train is from the trackside worker based on the first signal intensity // and the sound power PR.4. Method as claimed in claim 3, wherein the step of processing further comprises: iv) repeating steps i) to Hi) at a second point in time t2 to determine a second distance d2 the train is from the trackside worker; v) calculating the speed s of the train using s = 5. Method as claimed in claim 4, wherein the signal comprises airborne acoustic waves generated by a train horn.II6. Method as claimed in claim 5, wherein the portable signal detector comprises a microphone.7. Method as claimed in claim 4, wherein the signal comprises rail-borne acoustic waves generated by train wheels.8. Method as claimed in claim 7, wherein the portable signal detector comprises a vibration sensor.9. Method as claimed in claim 4, wherein the signal comprises an acoustic signature characteristic of a train.10. Method as claimed in claim 9, further comprising the step of: using the portable signal detector to record acoustic signatures to create training data for a machine-learning program.11. Method as claimed in claim 4, wherein the signal comprises a visual signal indicative of a train.12. Method as claimed in any preceding claim, wherein the step of triggering weara-ble alarm comprises: i) sending a signal from the portable signal detector to a central control centre warning of the approaching train; and ii) sending a signal from the central control centre to the wearable alarm to trigger an alarm.13. Method as claimed in any of claims 1 to 12, wherein the step of triggering weara-ble alarm comprises: i) sending a signal from the portable signal detector to the wearable alarm to trigger an alarm.14. Method as claimed in any preceding claim, wherein the wearable alarm comprises a vibration motor, light source and/or audible alarm.15. A portable signal detector adapted to detecting a signal indicating the movement of a train along a rail track toward a trackside worker, comprising: a housing; a sensor adapted to detect a signal indicating the movement of a train along a rail track toward a trackside worker; and a processor adapted to process the signal to determine at least a first signal inten- 1 0 sity h at a time t-/ for comparison with a reference source power PR to indicate the speed of the train and distance d/ the train is away from the trackside worker.