Computing the length of a railway vehicle or a train or a train of such vehicles

Abstract: In a railway signalling system, the length of a vehicle or train is computed by on board measurement of the distance travelled between detecting the passage of the front of the vehicle or train past a fixed point and detecting the passage of the rear of the vehicle or train past the same fixed point or a fixed point a known distance from the first.

Description: The present invention relates to computing the length of a railway vehicle or a train of such vehicles. The concept of replacing conventional railway signaling equipment by train carried, point controlling, and interlocking modules inter-connected by radio or other transmission medium is well known. There are however certain practical difficulties, missing elements, and unnecessary complications in the realisation of known systems. One such is the method of determining the location of the or rear of a train for the purposes of authorising a following train to proceed or of allowing a route which has been traversed to be released. In some known systems, train location is determined by an on-board train computer by a combination of reference wayside markers such as transponders, loop ends, loop transpositions or the like together with on-board distance measurement derived from an odometer, tachometer or equivalent device such as a reader of closely spaced track-side marks, plates or loop transpositions or the like. The location thus derived is reported to a wayside control computer which uses the information as the basis for generating movement authorities for transmission to trains with reference also to supervisory controls and fixed interlocking data. For the purpose of route release behind a train and to define the limit of proceed authority for a following train it is necessary for the control computer to deduce the location of the rear of the train. In a known system (GB-A-2 189 066), the control computer does this by reference to the "train consist" (i.e. the overall composition of the train) from which train length can be derived. In practice there are difficulties in ensuring that such information is in a sufficiently vital form for use in safety functions. It would be possible to provide equipment at the rear of the train equivalent to that at the front and to report the location of the rear of the train separately from the front, but this would be complicated and expensive and would double the number of mobile identities to be serviced by the communications system. It is also frequently impractical to locate appropriate equipment at the rear of a train. DE-B-1 232 610 discloses a system in which, for checking train completeness, means at the front of the train communicates with means at the rear of the train. According to the present invention, there is provided a system for computing the length of a railway vehicle or a train of such vehicles according to claim 1 the preamble of which corresponds to DE-C-2 830 672. Vehicle or train length may be used by the computing means to deduce and report the location of the rear of the vehicle or train, for example to a signalling control system or directly to a following vehicle or train; or alternatively the computing means may send the vehicle or train length to a signalling control system which will subsequently use it to deduce the location of the rear of the vehicle or train from a report from the computing means of the location of the front of the vehicle or train. Thus, a railway vehicle or train of such vehicles can measure its own length and use this information to deduce and report to a following vehicle or train, or to a signalling control system, or both, the location or clearance of its rear in relation to fixed points along the track or to pass a positive report of vehicle or train length to a signalling control system to enable the latter to effect subsequent route release and give proceed authorities to following vehicles or trains based on reports from the vehicle or train of the location of its front only. Vehicle or train length need be measured only at locations where trains may divide or vehicles attach or where journeys commence. The present invention will now be described, by way of example, with reference to the accompanying drawing, in which:- Fig. 1a) shows schematically an active trackside device; Figs. 1b) and 1c) shows respectively the front and rear of a train passing the device of Fig. 1a); Fig. 2a) shows schematically a passive trackside device; and Figs. 2b) and 2c) show respectively the front and rear of a train passing the device of Fig. 2a). Referring first to Figs. 1a), 1b) and 1c), a trackside device 11 such as a transponder reader or magnet detector detects a corresponding tail tag 12 mounted on the rear of a train 15 moving in the direction of arrow A and generates a train rear detection message which is transmitted by a radio transmitter 13 to a train computer 14 at the front of the train 15. The location of the trackside device 11 is first recorded by the train computer as the front of the train passes and detects either a related trackside marker 16 (such as a transponder) or the active trackside device 11 itself by means of a detector 17, which may be a transponder reader of known type also used for other signalling purposes. The train computer 14 tracks distance travelled as in known systems, for example by an odometer 18, and is therefore able to measure the distance travelled between detection of the trackside device 11 or its associated marker 16 and receipt of the train rear detection message from the trackside device 11. This distance corresponds to the train length. Any error arising from delays in transmission of the train rear detection message will result in excessive train length being measured, which is a safe error. Whether the measured train length is used by the train computer 14 to report the location of the rear of the train, or is transmitted by the train computer 14 to a wayside or centrally located control computer to enable it to deduce train rear location from train front location reports, some form of continuous monitoring is required to ensure that the train is complete, which for example may be continuous detection of a rear of train loop device via a train line 19 or may be continuous reception of a signal transmitted by radio or other means from a rear of train transmitter. Loss of monitoring will cause the train computer 14 to cease or modify train location reports so as to ensure that any detached train portion is protected by the signalling system. If a maximum train length can be defined, the system can be arranged to use this as a default value in the event of failure of the measuring function, thus enabling the rest of the signalling system to continue operation, albeit in a degraded mode. If the marker 16 is used, to be detected by detector 17, then the device 11 detected by tail tag 12 may be at a fixed point a known distance from marker 16. Referring to Figs. 2a), 2b) and 2c), in a second example, a passive trackside device 21 such as a transponder or magnet is detected by an active train rear mounted detecting arrangement 22 which generates a detection message which is transmitted by an associated radio transmitter 23 or train line or other medium to the train computer 14 at the front of the train. The location of the trackside device or a similar associated device, will first be recorded by the train computer when the front of the train passes it in a similar manner to the first example. Computation and subsequent application of train length information will be generally similar to the first example. Continuous detection of train rear may also be performed by part of the equipment which forms the active train rear mounted arrangement. The train rear mounted arrangement could detect a separate passive device at a fixed point a known distance from the device 21 detected by the equipment 17/18 at the front of the train.

Claims: A system for computing the length of a train (15) of railway vehicles, the system comprising: computing means (14) located on the train; distance measuring means (18) located on the train, said distance measuring means being coupled with said computing means for supplying thereto information dependent on distance travelled by the train; first detecting means (17), at the front of the train (15), for detecting trackside means (16 or 11,13) at a first fixed point to detect the passage of the front of the train past said first fixed point and transmitting a first indication to said computing means (14) in response to detecting the passage of the front of the train past said first fixed point; and second detecting means (22,23), for detecting the passage of the rear of the train (15) past said first fixed point or a second fixed point a known distance therefrom and transmitting a second indication to said computing means (14) in response to detecting the passage of the rear of the train past said first fixed point or said second fixed point, said computing means being arranged to compute a measure of the length of the train based on distance travelled by the train between reception by the computing means of said first and second indications, characterised in that: said second detecting means (22,23) comprises detecting means (22) at the rear of the train (15) for detecting trackside means (21) at said first fixed point or said second fixed point and transmission means (23) on the train for transmitting said second indication to said computing means (14). A system according to claim 1, wherein said transmission means (23) comprises radio transmission means. A system according to claim 1 or 2, wherein said computing means (14) is arranged for reporting the location of the rear of the train (15) based on knowledge of the location of the front of the train. A system according to claim 1 or 2, wherein said computing means (14) is arranged for reporting the length of the train (15) to a signalling control system so that the signalling or control system can subsequently deduce the location of the rear of the train from a report from the computing means of the location of the front of the train.

Inventors: MACDOUGALL DAVID BRUCE, MACDOUGALL, DAVID BRUCE
Applicants: WESTINGHOUSE BRAKE & SIGNAL, WESTINGHOUSE BRAKE AND SIGNAL HOLDINGS LIMITED
Application year: 1989
Main classification: B61L1
IPC codes: B61L1