GB2288051A - Detecting a railway vehicle - Google Patents

Abstract

To determine the presence, or absence, of a vehicle on a predetermined length of railway track, axle counting detectors 1, 3, 2 count the number of train wheels entering and leaving each of at least two adjacent sections X, Y, in turn, and control means 5 respond to the receipt of entry/leaving count data from the axle counting detectors to give an indication of the presence, or absence, of a vehicle on the track. Any difference in the entry/leaving count data for the first section is indicative of the presence of a vehicle on the first section and results in the entry count data for the first section being compared with the leaving count data for the other of the at least two sections. The control means give an indication of the absence of a vehicle on the at least two sections in the absence of any difference between the entry/leaving count data for the at least two sections. <IMAGE>

Description

A SYSTEM AND METHOD FOR DETECTING A RAILWAY VEHICLE This invention relates to a railway vehicle detection system and method for determining the presence, or absence, of a vehicle on a predetermined section of the railway track.

The conventional system for detecting the presence, or absence, of a railway vehicle on a predetermined section of a railway track is a fail-safe system, known as the 'track circuit', which involves the use of electrical circuits in the railway tracks. With this railway vehicle detection system, if a track circuit fails to operate, for whatever reason, then it is assumed, by the system, that the section of the railway track concerned is occupied. This will result in the signals, for this section of the railway track, to be held at red, i.e. a stop signal for any other on-coming railway vehicle.

A recent investigation into the causes of signalling failures on railway tracks, indicated that track circuits are one of the principle sources of failure, limiting the overall availability of signalling systems. Advances in electric propulsion technology for use in modern rolling stock have necessitated the use of increasingly sophisticated track circuit designs that rely on a variety of modulation and coding techniques in order to achieve the required degree of immunity to traction induced interference. Furthermore, it has been found that complex microprocessor based track circuit designs cannot achieve the same degree of reliability as the simple electromechanical designs that were formerly used for railway vehicle detection.In addition, rail connections are inherently vulnerable in any track circuit installation, as are the traditional problems such as flooding, leaf deposit and poor shunting performance of light rail vehicles. All of these problems mitigate against theoretical failure rate predictions being achieved in practice. Thus, the foregoing factors, when taken as a whole, suggest that railway vehicle detection systems based on track circuits do not necessarily offer the simple, reliable and cost effective means of railway vehicle detection that has formerly been taken for granted.

It is also known to use axle counters for determining the presence, or absence, of railway vehicles on a discrete section of a railway track. An axle counter system involves the use of detectors, situated one at each end of the section of track concerned, which are bolted to the track and which are used to count the number of wheels (not axles) passing thereover. The wheel count leaving a section of the railway track is subtracted from the wheel count entering the section. If the result is zero, then the section is deemed to be clear of railway vehicles.

The use of axle counter systems has, however, been restricted to a limited range of specialised applications where the use of track circuits was not viable due to civil constraints. These specialist applications involved the use of stand-alone axle counter sections of the railway track and of a dedicated evaluator unit for comparing the number of wheels entering the section with those leaving the section and operating a safety relay for interface to Solid State Interlocking (SSI) arrangements in the normal manner.

The associated capital cost of such systems greatly exceeded the cost of a functionally equivalent track circuit installation. A further disadvantage of these axle counter systems is that no firm conclusion can be drawn as to the state of occupancy of the section of the track in the event of a discrepancy occurring in the count values obtained from the two detection points.

It is an object of the present invention to provide a railway vehicle detection system that overcomes the abovementioned disadvantages of track circuit detection systems and the known axle counter systems by employing a fundamentally different approach to the use of axle counters. With the present invention, a decision concerning the presence, or absence, of a railway vehicle on a predetermined section of the railway track is made by a centralised interlocking processor arrangement on the basis of count data obtained from multiple axle counter detection points.

According to one aspect of the present invention, there is provided a railway vehicle detection system for determining the presence, or absence, of a vehicle on a predetermined length of the railway track including detection means, for at least two adjacent sections of the track, comprising axle counting detectors for counting the number of train wheels entering and leaving each of the said at least two adjacent section, in turn, and control means responsive to the receipt of entry/leaving count data from the axle counting detectors to give an indication of the presence, or absence, of a vehicle on the track, wherein any difference in the entry/leaving count data for the first of the said at least two sections to be detected is indicative of the presence of a vehicle on the first section and results in the entry count data for the first section being compared with the leaving count data for the other of the said at least two sections, and wherein the control means give an indication of the absence of a vehicle on the said at least two sections of the track in the absence of any difference between the entry/leaving count data for the said at least two sections.

According to another aspect of the present invention, there is provided a method for determining the presence, or absence, of a railway vehicle on a predetermined length of railway track including the steps of: - detecting the wheel count of a vehicle entering a first section of the said predetermined length of track; - detecting the wheel count of the vehicle leaving the said first section and entering an immediately adjacent section of the said predetermined length of track; - detecting the wheel count of the vehicle leaving the said adjacent section; - subtracting the leaving wheel count for the said first section from the entry wheel count for the said first section, any difference in the wheel counts being indicative of the presence of the vehicle on the said first section;; - in the event of a difference in the wheel counts for the said first section, subtracting the leaving wheel count for the said adjacent section from the entry wheel count of the said first section, the absence of a difference being indicative of the vehicle having passed through the predetermined length of track; and - in the absence of a difference in the wheel counts for the said first section and/or the said adjacent section, effect a change in the track signal for the predetermined length of track from a stop signal to a line free signal.

The foregoing and other features according to the present invention will be better understood from the following description with reference to the single figure of the accompanying drawings which diagrammatically illustrates a railway vehicle detection system according to the present invention.

As is diagrammatically illustrated in the single figure of the accompanying drawings, the railway vehicle detection system according to the present invention, includes axle counter detectors 1 to 3 which are secured, in a spacedapart relationship, to the railway track 4 and which define two adjacent sections 'X' and 'Y' of the track 4. The axle counter detectors 1 to 3 interface directly to a centralised control unit 5, including Solid State Interlocking (SSI) Axle Counter Modules, with no requirement for stand-alone evaluators for each of the sections 'X' and 'Y'.

As, and when, a railway vehicle travelling along the track 4, in the direction of the arrow 6, enters the section 'X' of the track, the axle counter detector 1 will count the number of wheels passing thereover. When the railway vehicle leaves section 'X' and enters the adjacent section 'Y', the axle counter detector 3 will count the number of wheels passing thereover. The entry/leaving count data respectively obtained by the detectors 1 and 3 for the section 'X' is evaluated by the centralised control unit 5.

Any difference in the count data obtained by the detectors 1 and 3 would normally result in section 'X' of the track being assumed to be blocked by a railway vehicle and thereby prevent further traffic from entering the section. However, with the system according to the present invention, the section 'X' of the track will be released, by the centralised control unit 5, for future use if the count data obtained from the axle counter detector 2 matches the count data obtained from the axle counter detector 1. Thus, in these circumstances, the detector 3 will be automatically reset, the control unit 5 will cause the traffic signals for sections 'X' and 'Y' of the track to be switched from red to green, i.e. to indicate to other on-coming railway vehicles that the sections of the track are free for use.

The advantage of this detection system is that miscounts and wheel detector failures need not result in sections of the track 4 becoming permanently occupied since count values obtained from subsequent axle counter detectors can be used to release the section of the track previously assumed to be occupied, i.e. adjacent track sections merge to form longer sections in the event of unacceptable data being obtained from individual detection points. The effect of detector failure is thus limited to a localised worsening in service headway (number of trains per hour) until the fault can be rectified, i.e. failures of the train system result in graceful degradation of the overall signalling system availability.

Automatic reconfiguration of the axle counters, should a failure occur, will further improve performance by ensuring graceful degradation of the system. The effect of a failure will thus be to increase the section length, i.e.

to the next axle counter, rather than hold a signal at red.

Line capacity will, therefore, be affected while journey times are unlikely to alter except when the line is operating at maximum capacity.

Thus, the railway vehicle detection system according to the present invention has the following technical and commercial advantages: - reduces the financial impact of train delays due to a gradual degradation of the railway vehicle detection system in the event of failures; - existing signalling systems can be used with the present invention thereby facilitating the testing and commissioning of system installations; - the present invention is immune to all forms of electric propulsion; - the present invention is immune to flooding, leaf deposit and poor shunting of light vehicles; and - elimination of impedance bonds.

The railway vehicle detection system according to the present invention is not limited to the use of two adjacent sections, as is diagrammatically illustrated in the single figure of the accompanying drawings. Any number of adjacent sections could be used with an axle counter detector at the interface of each pair of adjacent sections. For example, with three sections, the entry count data for the first of the three sections to be detected could, in the event of a difference being detected between the entry/leaving count data for the first section, be successively compared with the leaving count data for the second and third sections in order to verify the presence, or absence, of a vehicle.

Claims (5)

1. A railway vehicle detection system for determining the presence, or absence, of a vehicle on a predetermined length of the railway track including detection means, for at least two adjacent sections of the track, comprising axle counting detectors for counting the number of train wheels entering and leaving each of the said at least two adjacent section, in turn, and control means responsive to the receipt of entry/leaving count data from the axle counting detectors to give an indication of the presence, or absence, of a vehicle on the track, wherein any difference in the entry/leaving count data for the first of the said at least two sections to be detected is indicative of the presence of a vehicle on the first section and results in the entry count data for the first section being compared with the leaving count data for the other of the said at least two sections, and wherein the control means give an indication of the absence of a vehicle on the said at least two sections of the track in the absence of any difference between the entry/leaving count data for the said at least two sections.

2. A railway vehicle detection system as claimed in claim 1 wherein the system is adapted to detect the presence, or absence, of a vehicle on two adjacent sections of the railway track, wherein the detection means include a first axle counter detector at the interface of the two adjacent sections, a second axle counter detector at the entrance to the two adjacent sections, and a third axle counter detector at the exit of the two adjacent sections, wherein the control means are adapted to subtract the count data of the first detector from the count data of the second detector, any difference being indicative of the presence of a vehicle on the first of the two adjacent sections, and wherein, in the event of a difference between the count data of the first and second detectors, the control means are adapted to subtract the count data of the third detector from the count data of the second detector, the absence of a difference being indicative of the absence of a vehicle on the two adjacent sections of the track.

3. A railway vehicle detection system for determining the presence, or absence, of a vehicle on a predetermined length of the railway track substantially as hereinbefore described with reference to the single figure of the accompanying drawings.

4. A method for determining the presence, or absence, of a railway vehicle on a predetermined length of railway track including the steps of: - detecting the wheel count of a vehicle entering a first section of the said predetermined length of track; - detecting the wheel count of the vehicle leaving the said first section and entering an immediately adjacent section of the said predetermined length of track; - detecting the wheel count of the vehicle leaving the said adjacent section; - subtracting the leaving wheel count for the said first section from the entry wheel count for the said first section, any difference in the wheel counts being indicative of the presence of the vehicle on the said first section; ; - in the event of a difference in the wheel counts for the said first section, subtracting the leaving wheel count for the said adjacent section from the entry wheel count of the said first section, the absence of a difference being indicative of the vehicle having passed through the predetermined length of track; and - in the absence of a difference in the wheel counts for the said first section and/or the said adjacent section, effect a change in the track signal for the predetermined length of track from a stop signal to a line free signal.

5. A method for determining the presence, or absence, of a railway vehicle on a predetermined length of railway track substantially as hereinbefore described with reference to the single figure of the accompanying drawings.